USING SAME

FIELD OF THE INVENTION

This invention relates in general to the field of sensors and more specifically to sensors having resonating electrical circuits.

BACKGROUND OF THE INVENTION

Many applications require arrays (or groups) of sensors for mapping physical parameters such as pressure temperature, force and others in various measurement environments. Sensors (including miniature sensors) having an electrical circuit with a resonance frequency which varies as a function of a parameter in a measurement environment are well known in the art. For example, single sensors based on inductance capacitance type resonating electrical circuit (LC circuit) and configured as wireless sensors have been disclosed by C. C. Collins, in a paper entitled "Miniature passive pressure transensor for implanting in the eye," published in IEEE Trans. Biomed. Eng. , vol. BME-14, No. 2, pp. 74-83, Apr. 1967, incorporated herein by reference in it's entirety.

Additional types of electrically resonating sensors are disclosed in US patents 6,517,483 and 6,287,256, Incorporated herein by reference in their entirety.

Such sensors may include structural elements that function as part of an electrical resonating circuit (Typically an RLC type circuit having resistive capacitive and inductive elements, but LC circuits having inductive and capacitive elements may also be used). Usually, one or more of the components of the circuit may change its electrical properties as a function of the parameter to be measured in the measurement environment. For example, the capacitive component or element of the sensor may change it's capacitance as a function of the value of the measured parameter (such as, for example, the pressure within the measurement environment), or the inductance of the inductive component or element of the sensor may change as a function of the value of the measured parameter. Another possibility is that both the capacitive and inductive components of the sensors may change their capacitance and inductance, respectively, as a function of the value of the measured parameter. When the parameter to be measured changes, one or more of the components of the RLC or LC circuit of the sensor changes resulting in a change of the electrical resonance frequency of the sensor. The resonance frequency of the resonating electrical circuit of the sensor may be determined (for example, by applying to the electrical circuit of the sensor a probing electrical signal such as a chirp (which is a periodic electrical waveform having a varying frequency, for example a sinusoidal electrical signal of increasing or decreasing frequency over time) or a voltage step or a voltage pulse. The resonance frequency of the electrical circuit may be determined from the electrical response of the sensor to the applied probing electrical waveform as is known in the art.

Many applications require that multiple sensors need to be read in devices including such sensor arrays or sensor groups. Reading data from multiple sensors may be achieved in several ways. One way for reading the sensors of the array of sensors is to have a pair of electrical conductors (such as, electrically conducting wires) attached to each sensor in the array. In this method, each of the sensors is individually read by applying a probing electrical signal to the pair of wires of each sensor and reading the sensor's resulting response of each sensor. However, as the number of individual sensors in the array increases, the numerous pairs of wires required makes the connections to the sensors quite bulky, expensive and for some applications, impractical.

Furthermore, when a large number of such wire pairs is required, the sheer bulk of the numerous wires may make it impossible to implement this reading method in situations where the available space for accommodating these wires is limited (for example, in sensor arrays mounted in catheters for insertion into a body, the catheter lumen may have a very limited space therein for such wires due to size limitations and the need to accommodate other components in the catheter).

Another solution is to have the sensors connected is a row/column matrix structure and read each row/column crossing of the matrix. U.S. Patent 7,673,528 discloses a readable sensor matrix with multiple sensors. This type of structure works well for two dimensional sensor arrays but is limited to structures and sensors in which the change in one sensor may be read with no interference from neighboring adjacent sensors. Such a matrix type reading method may also be expensive to implement. Another solution for reading sensor arrays is to use sensors with integrated electronics. In this type of solution, each sensor has it's own unique digital address or signature, allowing the reading electronics to address each sensor separately over a single pair of wires common to the entire sensor array. However, such a reading method is quite complicated due to the need for additional expensive and sophisticated electronic circuitry needed at the level of each sensor for providing the sensor with the individual address or signature. Therefore, this method of sensor reading is not only expensive but also increases the probability of malfunction of each sensor due to the added electronic circuitry at the individual sensor level.

There is therefore a long felt need for sensors, sensor systems, and methods for reading the individual resonance frequencies of multiple electrically resonating sensors that overcome the limitations and disadvantages of the prior art sensors, sensor systems and sensor reading methods.

SUMMARY OF THE INVENTION

There is therefore provided, in accordance with an embodiment of the sensor arrays of the present application a sensor array including a plurality of sensors. Each sensor includes a resonating electrical circuit having a resonance frequency that varies as a function of a parameter in a measurement environment. The sensors are electrically coupled in parallel to a single pair of electrical conductors. Each sensor is tuned to resonate electrically in a range of resonance frequencies such that the electrical resonance frequency range of each sensor does not overlap with the electrical resonance frequency range of any other sensor of the plurality of sensors over the expected span of the measured parameter range in the measurement environment.

Furthermore, in accordance to an embodiment of the sensor array, the parameter is selected from the group consisting of pressure, temperature, strain, load, acceleration, proximity, and the dielectric constant of a fluid in the measurement environment.

Furthermore, in accordance to an embodiment of the sensor array, the resonating electrical circuit of each sensor of the sensor array is an RLC resonating electrical circuit. Furthermore, in accordance to an embodiment of the sensor array, the electrical resonating circuits of all sensors of the plurality of sensors are connected in parallel to the single pair of electrical conductors.

Furthermore, in accordance to an embodiment of the sensor array, the single pair of electrical conductors are a single pair of electrically insulated electrically conducting wires.

Furthermore, in accordance to an embodiment of the sensor array, the sensor array is selected from the group consisting of, a linear sensor array, a two dimensional sensor array, a three dimensional sensor array, and any combinations thereof.

Furthermore, in accordance to an embodiment of the sensor array, the sensors of the sensor array are selected from the group consisting of, a sensor comprising a resonating RLC electrical circuit having a capacitance that varies as a function of the value of the parameter to be measured, a sensor comprising a resonating RLC electrical circuit having a capacitance that varies as a function of the value of the parameter to be measured and an inductance that varies as a function of the value of the parameter to be measured, and a sensor comprising a resonating RLC electrical circuit having an inductance that varies as a function of the value of the parameter to be measured.

Furthermore, in accordance to an embodiment of the sensor array, the sensors of the sensor array are selected from the group consisting of, sensors that vary from each other in their electrical resonance frequency due to the sensors being of non-identical dimensions or non-identical construction, sensors having identical dimensions and structure wherein each sensor is a tunable sensor capable of being tuned to a selected electrical resonance frequency range by electrically connecting the sensor to a selected tuning electrical component, sensors that vary from each other in their electrical resonance frequency due to the sensors having identical dimensions and structure wherein the electrical resonance frequency of each sensor is determined by connecting it to an external tunable component having a tunable value of capacitance and/or inductance, and any combinations thereof.

Furthermore, in accordance to an embodiment of the sensor array, the sensors are tunable sensors and the tuning electrical component is selected from the group consisting of a tuning capacitor, a tuning inductor, and any combinations thereof. Furthermore, in accordance to an embodiment of the sensor array, the sensors are tunable sensors and wherein the tuning electrical element is a laser trimmable electrical component.

Furthermore, in accordance to an embodiment of the sensor array, the sensors of the sensor array are compensated sensors configured to compensate for the effects of varying of at least one physical parameter in the measurement environment on the resonance frequency of the sensors.

Furthermore, in accordance to an embodiment of the sensor array, the sensors of the sensor array are compensated sensors selected from the group consisting of, compensated sensors wherein each compensated sensor comprises a reference sensor therein, compensated sensors, wherein the array comprises one reference sensor and wherein each of the compensated sensors is compensated using compensating data obtained from the reference sensor, grouped compensated sensors, wherein the array comprises a plurality of reference sensors and wherein the sensors are grouped into several sensor groups wherein each of the sensors in a sensor group is compensated by data from a single reference sensor allocated to the sensor group.

There is also provided in accordance with an embodiment of the methods of the present application a method of constructing a sensor array. The method includes the steps of: providing a plurality of sensors, each sensor includes a resonating electrical circuit having a resonance frequency that varies as a function of a parameter in a measurement environment, tuning each sensor to resonate in a different range of resonance frequencies, such that the resonance frequency range of each sensor does not overlap with the resonance frequency range of any other sensor of the plurality of sensors over the expected span of the measured parameter range in the measurement environment, and electrically connecting all sensors of the plurality of sensors in parallel to a single pair of electrical conductors for providing electrical exciting signals to the sensors.

Furthermore, in accordance to an embodiment of the method for constructing a sensor array, the parameter is selected from the group consisting of pressure, temperature, strain, load, acceleration, proximity, the dielectric constant of a fluid in the measurement environment. Furthermore, in accordance to an embodiment of the method for constructing a sensor array, the resonating electrical circuit of each sensor of the sensor array is an RLC resonating electrical circuit.

Furthermore, in accordance to an embodiment of the method for constructing a sensor array, the sensor array is selected from the group consisting of, a linear sensor array, a two dimensional sensor array, a three dimensional sensor array, and any combinations thereof.

Furthermore, in accordance to an embodiment of the method for constructing a sensor array, the sensors of the sensor array are selected from the group consisting of, a sensor comprising a resonating RLC electrical circuit having a capacitance that varies as a function of the value of the parameter to be measured, a sensor comprising a resonating RLC electrical circuit having an inductance that varies as a function of the value of the parameter to be measured, a sensor comprising a resonating RLC electrical circuit having a capacitance that varies as a function of the value of the parameter to be measured and an inductance that varies as a function of the value of the parameter to be measured.

Furthermore, in accordance to an embodiment of the method for constructing a sensor array, the sensors of the sensor array are sensors that vary from each other in their resonance frequency due to the sensors being of non-identical dimensions or non-identical construction and the step of tuning includes selecting different sensors from a plurality of available sensors such that each selected sensor has a different resonance frequency range which does not overlap the resonance frequency range of any other sensor of the plurality of sensors of the sensor array.

Furthermore, in accordance to an embodiment of the method for constructing a sensor array, the sensors are identical tunable sensors and the step of tuning includes electrically connecting at least some of the sensors to a tuning electrical component selected from a plurality of available different tuning electrical components such that each sensor has a different resonance frequency range which does not overlap the resonance frequency range of any other sensor of the plurality of sensors of the sensor array.

Furthermore, in accordance to an embodiment of the method for constructing a sensor array, the sensors are identical sensors. All or some of the identical sensors are electrically coupled to a tunable electrical component. The step of tuning includes tuning the tunable electrical components such that each sensor has a different resonance frequency range which does not overlap the resonance frequency range of any other sensor of the plurality of sensors of the sensor array.

Furthermore, in accordance to an embodiment of the method for constructing a sensor array, the tuning electrical component is selected from a tuning capacitor, a tuning inductor, and a combination of a tuning capacitor and a tuning inductor.

Furthermore, in accordance to an embodiment of the method for constructing a sensor array, the sensors of the sensor array are compensated sensors configured to compensate for the effects of varying of at least one physical parameter in the measurement environment on the resonance frequency of the sensors.

There is also provided, in accordance with the methods of the present application, a method for operating a sensor array in a measurement environment. The method includes the steps of: providing a sensor array including a plurality of sensors. Each sensor includes a resonating electrical circuit having a resonance frequency that varies as a function of a parameter in the measurement environment. Each sensor of the plurality of sensors is electrically coupled in parallel to a single pair of electrical conductors. Each sensor is tuned to resonate in a different range of resonance frequencies such that the resonance frequency range of each sensor does not overlap with the resonance frequency range of any other sensor of the plurality of sensors over the expected span of the measured parameter range in the measurement environment, positioning the sensor array in a measurement environment, applying an exciting electrical signal to the sensor array through the single pair of electrical conductors, determining a plurality of frequency values associated with a plurality of amplitude minima in an electrical response signal sensed in response to the step of applying, and determining the value of the measured parameter for each sensor in the sensor array from the determined plurality of frequency values.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the step of applying includes applying a chirp electrical signal to the sensor array and the first step of determining includes the steps of processing the response signal to determine a plurality of frequencies associated with a plurality of amplitude minima in the response signal, wherein each frequency of the plurality of frequencies is associated with the resonance frequency of a sensor in the sensor array and wherein the second step of determining includes determining the value of the measured parameter for each sensor of the sensors of the array from the plurality of frequencies.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the chirp electrical signal is a chirp signal having a frequency range spanning the entire range of the resonance frequencies of all the sensors of the sensor array over the entire range of parameter's values that need to be determined in the measurement environment.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the first step of determining comprises the steps of processing the response signal to obtain frequency points from the amplitude minima of the signal and from the frequency of the chirp at the corresponding times of said amplitude minima.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the amplitude of the chirp signal is selected from a constant amplitude chirp signal, a variable amplitude chirp signal, a chirp having a rising frequency, a chirp having a falling frequency, and combinations thereof.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the electrical chirp signal is selected from, a chirp signal having a frequency that varies linearly with time and a chirp signal having a frequency that varies non-linearly with time.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the response electrical signal is sensed on a common resistor connected in series to an electrical conductor of the single pair of electrical conductors.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the step of applying includes applying an electrical signal selected from an electrical step signal and a square wave electrical signal to the pair of electrical conductors, and the first step of determining includes the steps of processing the response signal to determine a plurality of frequencies at which minima occur in a spectral representation of the response signal, wherein each determined frequency of the plurality of frequencies is associated with the resonance frequency of a sensor of the sensor array and determining the value of the measured physical parameter for each of the sensors of the array from the determined frequencies.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the spectral representation is obtained by performing a spectral analysis of the response signal.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the spectral analysis of the response signal is performed using a spectral analysis method selected from the group consisting of, a Fourier transform method, a wavelet based spectral analysis method, a multitaper spectral analysis method, a Pepisode spectral analysis method and a smooth periodogram method.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the step of processing includes processing the frequencies of the minima to obtain values of the measured parameter for each sensor by using a method selected from the group consisting of, using a look-up table to determine the value of the measured parameter for each of the sensors of the sensor array, computing the value of the measured parameter for each of the sensors using a calibration function, and using a calibration curve for determining the value of the measured parameter for each of the sensors.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the step of processing includes computing a compensated value of the measured parameter from the frequency associated with a sensor and from the frequency of at least one sensor of the sensor array having a resonance frequency representing the value of a second parameter of the measurement environment different from the measured parameter being determined.

Furthermore, in accordance to an embodiment of the method of operating a sensor array, the parameter being determined is pressure and the second parameter is temperature.

There is also provided in accordance with an embodiment of the sensor arrays of the present application, a sensor array including a plurality of sensors, each sensor comprises a resonating electrical circuit having a resonance frequency that varies as a function of a parameter in a measurement environment. The sensor array includes at least two groups of sensors. All the sensors in each group of sensors of the at least two groups of sensors are electrically connected in parallel to a different pair of electrical conductors of a plurality of pairs of electrical conductors. The sensors of each group of sensors are tuned to resonate electrically in a range of resonance frequencies such that the electrical resonance frequency range of each sensor in a group of sensors does not overlap with the electrical resonance frequency range of any other sensor of the group of sensors sharing the same pair of electrical conductors over the expected span of the measured parameter range in the measurement environment.

Furthermore, in accordance with an embodiment of the sensor arrays of the present application, each group of sensors of the at least two groups of sensors, is connected to a different sensor reading unit selected from a plurality of sensor reading units through the pair of electrical conductors connected in parallel to the sensors of the group.

Furthermore, in accordance with an embodiment of the sensor arrays of the present application, each different circuit reading unit of the plurality of circuit reading units is configured to apply exciting electrical signals to all the sensors of the sensor group connected to the circuit reading unit and each reading unit is configured to receive a response electrical signal from the sensor group connected thereto. All the different circuit reading units are electrically connected to a processor/controller unit for controlling the operation of the different circuit reading units and for receiving the response signals from the circuit reading units and processing the response signals to determine the value of the measured parameter for each sensor of the sensor array.

Furthermore, in accordance with an embodiment of the sensor arrays of the present application, each of the circuit reading units of the plurality of circuit reading units is configured for applying to the sensor group connected thereto an exciting electrical signal selected from, a pulse exciting signal, a square wave exciting signal, a rising step exciting signal, and a falling step exciting signal. The processor/controller unit is configured to receive the response signal generated in response to the exciting signal, to process the received response signal to obtain a spectral analysis thereof and to determine from frequency points of amplitude minima of the spectral analysis the value of the parameter for each sensor of the sensor group. Furthermore, in accordance with an embodiment of the sensor arrays of the present application, the spectral analysis of the response signal is performed using a spectral analysis method selected from the group consisting of, a Fourier transform method, a wavelet based spectral analysis method, a multitaper spectral analysis method, a Pepisode spectral analysis method and a smooth periodogram method.

Furthermore, in accordance with an embodiment of the sensor arrays of the present application, each of the different circuit reading units is configured for applying to the sensor group connected thereto an exciting a chirp exciting signal having a frequency range spanning at least the entire range of the resonance frequencies of all the sensors of the sensor group connected to the reading unit over the entire range of parameter's values that need to be determined in the measurement environment, and the processor/controller unit is configured to receive the response signal generated in response to the chirp signal, to process the received response signal to determine a plurality of frequencies at which the response signal has amplitude minima and to determine from the plurality of frequencies the value of the parameter for each sensor of the sensor group connected to the reading unit.

Furthermore, in accordance with an embodiment of the sensor arrays of the present application, all the pairs of electrical conductors connecting the sensors of the sensor groups are controllably electrically connectable to a single circuit reading unit by a multiplexer unit. The multiplexer unit is electrically connected to a controller/processor unit. The processor/ controller unit is configured for controlling the operation of the multiplexer unit, for sequentially receiving from the circuit reading unit response electrical signals received from a group of sensors selected from the at least two groups of sensors, in response to the application of an exciting electrical signal to the sensor group by the circuit reading unit through the multiplexer unit. The processor/controller is also configured for processing the received response signals to determine the value of the measured parameter for each sensor of the sensor array.

Furthermore, in accordance with an embodiment of the sensor arrays of the present application, the single circuit reading unit is configured for applying to any selected sensor group connected thereto through the multiplexer unit a chirp exciting signal having a frequency range spanning at least the entire range of the resonance frequencies of all the sensors of the sensor array over the entire range of parameter's values that need to be determined in the measurement environment, and wherein the processor/controller unit is configured to receive the response signal generated in response to the exciting signal, to process the received response signal to determine a plurality of frequencies at which the response signal has amplitude minima and to determine from the plurality of frequency points the value of the parameter for each sensor of the selected sensor group.

Furthermore, in accordance with an embodiment of the sensor arrays of the present application, the single circuit reading unit is configured for applying to a selected sensor group connected thereto through the multiplexer unit an exciting electrical signal selected from, a pulse exciting signal, a square wave exciting signal, a rising step exciting signal, and a falling step exciting signal, and the processor/controller unit is configured to receive the response signal generated in response to the exciting signal, to process the received response signal to obtain a spectral analysis thereof and to determine from frequency points of amplitude minima of the spectral analysis the value of the parameter for each sensor of the selected sensor group.

Furthermore, in accordance with an embodiment of the sensor arrays of the present application, the spectral analysis of the response signal is performed using a spectral analysis method such as, a Fourier transform method, a wavelet based spectral analysis method, a multitaper spectral analysis method, a Pepisode spectral analysis method and a smooth periodogram method.

Finally, in accordance with an embodiment of the sensor arrays of the present application, the processor controller unit is configured for controlling the operation of the multiplexer unit and of the single circuit reading unit, such that the multiplexer unit sequentially connects each of the at least two groups of sensors of the sensor array to the circuit reading unit and the single circuit reading unit applies the exciting signals to each selected group of sensors, until the processor/controller unit determines the value of the measured parameter for each of the sensors of the sensor array.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings, in which like components are designated by like reference numerals, wherein:

Fig. 1 is a schematic isometric view illustrating part of a cut-open prior art pressure sensor including an RLC electrical circuit with a fixed inductance and a capacitance that varies as a function of the pressure in a measurement environment, and a schematic diagram representing an electrical circuit representing the electrical properties of the sensor;

Fig. 2 is a schematic isometric view illustrating part of a cut-open prior art pressure sensor including an RLC electrical circuit with a an inductance and a capacitance that vary as a function of the pressure in a measurement environment, and a schematic diagram representing an electrical circuit representing the electrical properties of the sensor;

Fig. 3 is a schematic diagram illustrating a group of sensors connected in parallel to a sensor reading circuit in accordance with an embodiment of the sensors, sensor systems and sensor arrays of the present application;

Fig. 4 is a schematic diagram illustrating a group of sensors connected in parallel to a sensor reading circuit in accordance with another embodiment of the sensor systems of the present application;

Figs. 5-6 are schematic diagrams illustrating sensor arrays having a plurality of sensors and a plurality of tuning capacitors, in accordance with another embodiment of the sensor arrays of the present application;

Figs. 7-8 are schematic diagrams illustrating sensor arrays having a plurality of sensors and a plurality of tuning inductors, in accordance with yet another embodiment of the sensor arrays of the present application;

Figs. 9-10 are schematic block diagrams illustrating two different systems of sensors having multiple sensor groups electrically connected to multiple wire pairs, in accordance with two additional embodiments of the sensor systems and sensor arrays of the present application; Fig. 11 is a schematic diagram illustrating a three sensor array system circuit simulated by the SPICE LT program;

Fig. 12 is a schematic graph illustrating the simulated response of the circuit of Fig. 11 to a chirp signal;

Fig. 13 is a schematic graph illustrating the details of part of the curve 210 of Fig. 12 on an different time scale;

Fig. 14 is a schematic graph illustrating part of the FFT of the simulated response of Fig. 12;

Fig. 15 is a schematic diagram illustrating a three sensor array system circuit simulated by the SPICE LT program;

Fig. 16 is a schematic graph illustrating the simulated response of the simulated circuit of Fig. 15 to a rising voltage step signal;

Fig. 17 is a schematic graph illustrating the details of part of the curve 180 of Fig. 16; Fig. 18 is a schematic graph illustrating part of the FFT of the simulated response of Fig. 16.

Fig. 19 is a schematic graph illustrating part of the FFT curve of Fig. 18 on an expanded scale;

Fig. 20 is a schematic diagram illustrating a three sensor array system circuit simulated by the SPICE LT program;

Fig. 21 is a schematic graph illustrating the simulated response of the circuit of Fig.

20 to a square pulse signal;

Fig. 22 is a schematic graph illustrating the details of part of the curve 210 of the graph of Fig. 21 ;

Fig. 23 is a schematic graph illustrating part of the FFT of the simulated response of Fig. 21 ; and

Fig. 24 is a schematic block diagram illustrating the steps of a method for operating a sensor array in a measurement environment in accordance with an embodiment of the methods of the present application. DETAILED DESCRIPTION OF THE INVENTION

Notation Used Throughout:

The following notation is used throughout this document.

Term Definition

μΗ MicroHenry

Microsecond

FFT Fast Fourrier Transform

H Henry

Hz Hertz

MHz Megahertz

ms Millisecond

nF Nano farad

RLC Resistor inductor capacitor

V Volt

The current application provides sensors, sensor systems (and/or sensor array systems) and methods for reading the sensors of multiple sensor arrays, that allow the reading of multiple sensors using a single pair of electrical conductors. The methods may be implemented for in sensor arrays or sensor groups which include multiple sensors of the type that includes a resonating electrical circuit (such as an RLC electrical circuit or an LC circuit). The sensors of the present application are sensors that change their capacitance and/or inductance in response to changes in the physical variable to be measured. When either the inductance L or the capacitance C ( or both L and C) of the RLC circuit of the sensor changes, the resonance frequency of the sensor changes. For each sensor, the range of values within which the circuit's resonance frequency may vary is determined by the sensor's RLC circuit parameters L and C (the lumped circuit inductance and the lumped circuit capacitance, respectively).

The sensor arrays of the present application include multiple sensors. Each of the sensors is constructed (and/or tuned) such as it has unique RLC circuit values (or unique LC circuit values). The sensors of a sensor array are connected in parallel to a single pair of electrical conductors (such as, for example to a single pair of electrically insulated electrically conducting wires. It is noted that the construction of sensors and micro-sensor having electrically resonating circuits of the LC or RLC type is well known in the art, is not the subject of the present invention and is therefore only briefly discussed below with reference to Figs. 1-2 illustrating two well known different types of electrically resonating pressure sensors.

Reference is now made to Figs. 1-2. Fig. 1 is a schematic isometric view illustrating part of a cut-open prior art pressure sensor including an RLC electrical circuit with a fixed inductance and a capacitance that varies as a function of the pressure in a measurement environment, and a schematic diagram representing an electrical circuit representing the electrical properties of the sensor.. Fig. 2 is a schematic isometric view illustrating part of a cut-open prior art pressure sensor including an RLC electrical circuit with a an inductance and a capacitance that vary as a function of the pressure in a measurement environment, and a schematic diagram representing an electrical circuit representing the electrical properties of the sensor.

Turning to Fig. 1, the pressure sensor 2 includes a layer of substrate 4 that may be made from a stiff material, such as for example, silicon. The sensor 2 also includes a shaped flexible elastic member 6 which is made from a relatively elastic material such as for example, Kapton®. The flexible member 6 is sealingly attached to the substrate 4 by any suitable attachment method, such as to leave a small gap between the substrate and a part or portion of the shaped flexible member 6.

The method for sealingly attaching the flexible member 6 to the substrate 4 may be any suitable attachment method known in the art. It is noted that the attaching of the flexible member 6 to the substrate 4 results in a sealed chamber 8 being formed within the sensor 2 (only part of the sealed chamber 8 may be seen in the cut-open isometric view of part of the sensor of Fig. 1). The sealed chamber 8 is sealingly and fluidically isolated from the environment outside the sensor 2.

A first electrically conductive coil and plate pattern 10 is formed on the internal surface 6A of the flexible member 6. The coil and plate pattern 10 has thin coil portions 10A and a plate pattern IOC electrically connected to each other. A second electrically conductive coil and plate pattern 12 is formed on the surface 4 A of the substrate 4 facing the internal surface of the flexible member 6. The coil and plate pattern 12 has thin coil portions 12A and a plate pattern 12C electrically connected to each other When the sensor 2 is constructed, the elastic member 6 is aligned with the substrate 4 such that the windings of the coil portions 10A are positioned over the corresponding coil portions 12A of the pattern 12, and the plate portion IOC is positioned over the plate portion 12C. However, the coil portions 10A are spaced apart from the coil portions 12A such that there is a small (electrically insulating) gap between them (or an insulating material) and they do not contact each other and are electrically insulated. Similarly, the plate portion 10 is spaced apart from the plate portion 12C

The coil and plate patterns 10 and 12 may be made from any suitable type of electrically conducting material such as gold and the like. The coil and plate patterns 10 and 12 are electrically connected in series (the connection of the pattern 10 to the pattern 12 is not shown in the isometric view of Fig. 1) such that the two coil and plate patterns 10 and 12 for a two terminal RLC electrical circuit in which the resistor RSI represents the lumped electrical resistance of the sensor 2, the inductance LSI represents the lumped inductance of the sensor 2 and the variable capacitor CS1 represents the varying lumped capacitance of the sensor 2.

When pressure is increased in the measurement environment in which the sensor 2 is disposed, the elastic member 6 is pushed towards the stiff substrate 4 such that the plate portion IOC is pushed closer to the plate portion 12C thereby decreasing the distance separating between the plate portions IOC and 12C (which are actually a capacitor) and increasing the capacitance CS 1 of the sensor 2. If the pressure is decreased (below the pressure inside the sealed chamber 8), part of the elastic member 6 is pushed out and away from the stiff substrate 4 increasing the distance separating the plate portions IOC and 12C and decreasing the capacitance CS1. Thus, the resonance frequency of the RLC circuit of Fig. 1 will vary as a function of the pressure in the measurement environment due to the change in the RLC circuit's capacitance as a function of the pressure.

It is noted that while the capacitance of the RLC circuit of Fig. 1 varies as a function of the distance between the plate portions IOC and 12C, the distance between the coil portions 10A and 12A of the sensor is permanently fixed irrespective of the outside pressure values because the portions of the elastic member 6 which include the coil portions 10A are fixedly attached to the corresponding underlying portions of the substrate 4 such that there is no change in the distance separating the coil portions 10A from the coil portions 12A irrespective of the pressure value outside the sensor 2.

Thus, the resonance frequency of the electrical RLC circuit of the sensor 2 varies as a function of the pressure outside the sensor 2 because both the capacitance CS2 varies as a function of the pressure outside the sensor 2.

Turning to Fig. 2, the pressure sensor 32 includes a layer of substrate 34 that may be made as disclosed hereinabove for the sensor 2 of Fig. 1. In the specific (non-limiting) example of the sensor 32, the substrate layer 34 is made from silicon and is covered by a thin layer 34A of electrically insulating silicon dioxide formed on the surface of the substrate 34 in order to electrically insulate the electrically conductive silicone from any electrically conducting structures formed on the substrate 34. The sensor 32 also includes a shaped flexible elastic member 36 which is made from a relatively elastic material as disclosed in detail hereinabove for the elastic member 6 of Fig. 1.

The flexible member 36 is sealingly attached to the substrate 34 by any suitable attachment method, such as to leave a gap between the substrate 34 most of or a portion of the shaped elastic member 36.

The method for sealingly attaching the flexible member 6 to the substrate 34 may be any suitable attachment method known in the art as disclosed in detail hereinabove for the elastic member 6 of Fig. 1. It is noted that the attaching of the flexible member 36 to the substrate 34 results in a sealed chamber 38 being formed within the sensor 32 (only part of the sealed chamber 38 may be seen in the cut-open isometric view of part of the sensor of Fig. 1). The sealed chamber 38 is sealingly and fluidically isolated from the environment outside the sensor 32.

A first electrically conductive coil and plate pattern 40 is formed on the internal surface of the flexible member 36. The coil and plate pattern 40 has thin coil portions 40A and a plate pattern 40C electrically connected to each other. A second electrically conductive coil and plate pattern 42 is formed on the surface 34B of the silicon dioxide layer 34A facing the internal surface 36A of the elastic member 36. The coil and plate pattern 42 has thin coil portions 42A and a plate pattern 42C electrically connected (in series) to each other. When the sensor 32 is constructed, the elastic member 36 is aligned with the substrate 34 such that the windings of the coil portions 40A are positioned over the corresponding coil portions 42A of the pattern 42 and the plate portion 40C is positioned over the plate portion 42C. The coil portions 40A are spaced apart from the coil portions 42A such that there is a gap between them and they do not contact each other as seen in Fig. 2. Similarly, the plate portion 40C is spaced apart from the plate portion 42C as seen in Fig. 2.

The coil and plate patterns 40 and 42 may be made from any suitable type of electrically conducting material. The coil and plate pattern 40 and 42 are electrically connected in series such that the two coil and plate patterns 4 and 42 form a two terminal RLC electrical circuit in which the resistor RS2 represents the lumped electrical resistance of the sensor 32, the inductance LS2 represents the variable lumped inductance of the sensor 32 and the variable capacitor CSl represents the varying lumped capacitance of the sensor 32.

When pressure is increased in the measurement environment in which the sensor 32 is disposed, the elastic member 36 is pushed towards the stiff substrate 34 such that the plate portion 40C is pushed closer to the plate portion 42C thereby decreasing the distance separating between the plate portions 40C and 42C (which are actually a capacitor) and increasing the capacitance CS2 of the sensor 32. At the same time, the inductance of the coil formed from the coil portions 40A and 42A increases because of the reduction of the distance between the coil portions 40A and 42A, thereby increasing the lumped inductance LS2 of the RLC circuit of Fig. 2.

If the pressure is decreased (below the pressure inside the sealed chamber 38), part of the elastic member 66 is pushed out and away from the stiff substrate 34 increasing the distance separating the plate portions 40C and 42C and decreasing the lumped capacitance CS2 of the RLC circuit of the sensor 32. Thus, the resonance frequency of the RLC circuit of Fig. 2 will vary as a function of the pressure in the measurement environment due to the change in the RLC circuit's capacitance and inductance as a function of the pressure.

Thus, the resonance frequency of the electrical RLC circuit of the sensor 32 varies as a function of the pressure outside the sensor 32 because both the capacitance CS2 and the Inductance LS2 vary as a function of the pressure outside the sensor 32. When using electrically resonating sensors of the types known in the art and described hereinabove, the electrical resonance frequencies of each sensor can be measured by measuring the frequency response of each sensor individually (by electrically connecting each sensor to a separate pair of electrical conductors, applying an electrical signal to the circuit and then determining the resonance frequency of the sensor from the resulting circuits electrical response by suitably processing the circuit's response to the applied signal. As is well known in the art, the processing of the circuit's electrical response to determine the resonance frequency of the circuit may be performed in several different ways depending, inter alia, on the type of the electrical signal applied to the sensor's electrical circuit.

For example, if the electrical signal applied to the sensor is a chirp signal, the sensor's response (in the time domain) will have minimum amplitude corresponding to the sensor's electrical resonance frequency. In such a case, any method known in the art for determining a minimum may be applied to the response signal to determine the frequency at which the circuit's response has an amplitude minimum (which corresponds to the sensor's resonance frequency).

In another example, if the electrical signal applied to the sensor is a step signal (a rising step or a falling step may be used) or a pulse signal or a square wave signal, the electrical resonance frequency of the sensor may be determined by, subjecting the resulting sensor's electrical circuit response to any suitable frequency domain signal analysis methods, such as, for example, Fourier Transform (FT), Fast Fourier Transform analysis (FFT), wavelet spectral analysis, Multitaper spectral analysis, Pepisode spectral Analysis, and the like to determine the resonances frequency of the sensor. It is noted that such time domain and frequency domain analysis methods are well known in the art, are not the subject matter of the present application and are therefore not disclosed in detail hereinafter. As the resonance frequency of each sensor correlates to the physical parameter of interest to which the sensor is exposed, a map these parameters can be created.

It has occurred to the inventor of the present invention that connecting all sensors of a group of sensors (or of an array of sensors) to a single pair of electrical conductors may overcome the problems of the prior art methods by eliminating the necessity of dedicating a single pair of electrical conducting to each sensor. However, there is a problem in achieving such a simple reading layout because if the RLC circuits of the sensors are similar to each other (such as , for example, if all the sensors in the array are electrically identical within manufacturing tolerances), it becomes impossible to distinguish between the signals of different sensors because they will all resonate at the same or at quite close frequencies, making it practically impossible to tell, which resonance frequency should be attributed to which sensor.

To overcome this problem, the present invention enables a group of several sensors to be simultaneously read by electrically connecting all the sensors of the sensor group in parallel to a single pair of electrical conductors and by constructing the sensors such that each sensor has a uniquely identifiable electrical resonance frequency range. This may be achieved by constructing the sensors in a manner that ensures that each individual sensor is tuned or preset to resonate in a range of electrical resonance frequencies such that the electrical resonance frequency range of each sensor does not overlap with the electrical resonance frequency range of any other sensor of the group of sensors over the expected span of the measured parameter range (such as, for example, the pressure range) in the measurement environment. Such sensor arrays are also referred to hereinafter as "tuned sensor array" or "Tuned Sensor Arrays" because the sensors may be selected or tuned such that the electrical resonance frequency range of each sensor does not overlap with the electrical resonance frequency range of any other sensor of the group of sensors over the expected span of the measured parameter range.

Reference is now made to Fig. 3 which is a schematic diagram illustrating a group of sensors connected in parallel to a sensor reading circuit in accordance with an embodiment of the sensors, sensor systems and sensor arrays of the present application. The sensor system 50A includes a reading unit 60A electrically coupled to a group of N sensors SI, S2,....SN trough a single pair of electrical conductors 52 and 54. The Electrical conductors 52 and 54 may be a suitable pair of (preferably insulated) electrically conducting wires but may also be any other suitable electrically conducting members, such as but not limited to, metal lines on a PCB board, or metallic or non- metallic conducting lines deposited on a semiconducting substrate or on any other suitable substrate (such as, but not limited to, a glass substrate, an insulated metal substrate, a plastic substrate, a suitable polymer based substrate, a glass and epoxy composite substrate and the like). Each of the sensors SI, S2...SN is illustrated as having a capacitor (CI , C2,...CN, respectively), an inductor (LI , L2,....LN, respectively) and a resistor (Rl, R2,....RN, respectively). The capacitor of each sensor represents the lumped capacitance of the RLC circuit of the sensor. The inductor represents the lumped inductance of the RLC circuit of the sensor and the resistor of each sensor represents the lumped resistance of the sensor.

The reading unit 60A includes signal generating unit 62 and a response reading unit 64. The signal generating unit 62, may be any device that is capable of generating a suitable excitation signal(s), such as, for example, a chirp or a step signal or a Squarej wave signal (it is noted that in a square wave signal one can use the rising edge or the falling edge of the square wave or both as the exciting signal), and the like, and the response reading unit 64 may be any device that reads the circuit's response to the signal applied to the pair of conductors 52 and 54. The construction and operation of the signal generating unit 62 and of the response reading unit 64, is well known in the art, is not the subject matter of the present invention and is therefore not described in detail hereinafter. Many types of such devices may be used, such as any suitable commercially available function generator for generating signals across a load. The response reading unit 64 may be any analog or digital voltmeter or ampere-meter or an analog to digital converter and the like, and may have signal storing and processing capabilities. Any one of the signal generating unit 62 and of the response reading unit 64 of the reading unit 60A may include a processing unit (not shown) or microprocessor (not shown) or may be suitably connected to a processing unit and/or a computer or processor or microprocessor for controlling the operation of the reading unit 60A and/or for acquiring and/or processing the electrical responses read out of the circuit in response to the signal applied by the signal generating unit 62. Such a controller and/or processor unit may also control the operation of the signal generating unit 62 with regard to generation of t5he exciting signal.

In accordance with one embodiment of the systems of the present application, the RLC circuit characteristics of each sensor is implemented in a way that each individual sensor is tuned or preset to resonate in a range of electrical resonance frequencies, such that the electrical resonance frequency range of each sensor does not overlap with the electrical resonance frequency range of any other sensor of the group of sensors Sl-SN over the expected span of the measured parameter range (such as, for example, the pressure range, if the sensors are pressure sensors) in the measurement environment. It should be noted that the electrical resonance frequencies of the sensor system 50A are affected by both the electrical parameters of the individual sensor units SI, S2,...,SN, as well as by the parasitic RLC values of all the other components included in the system 50A.

The inventor has contemplated two different embodiments of such a sensor system that both ensure that each of the sensors SI, S2, ... , SN will have a distinct and non- overlapping range of resonance frequencies over the expected span of the measured parameter range in the measurement environment.

In a first embodiment of the sensor system, each of the sensors SI , S2, .... ,SN is a differently structured sensor which is manufactured to have different and distinct electrical RLC properties. This may be done by constructing each of the sensors to have different internal capacitors (such as, for example, by constructing the sensors to have different sizes of the plate portions 40C and 402C of the sensor 32 of Fig. 2), and/or different length(s) and/or different dimensions of the coil portions 40A and/or 42A of the sensor 32 of Fig. 2), and the like.

It is noted changing the dimensions of the plate portions 40A and/or 42A in order to change the capacitance or changing the dimensions of the may also result in change in their electrical resistance effectively changing both capacitance and resistance of the RLC circuit or both the inductance and resistance of the RLC circuit, or all three parameters of the RLC circuit (capacitance, inductance and resistance) simultaneously.

However, in accordance with yet another embodiment of the sensor system, the changes in the electrical properties of each sensor may also be achieved by modifying (increasing or decreasing) the dimensions of the entire sensor structure, in order to enable an increasing or decreasing in the total elastic member area and/or the substrate area available for carrying the conducting pathways, (such as, for example, the coil portions 40A and 42A and/or the plate portions 40C and 42C). In this embodiment the lumped capacitance of the different sensors may be changed by suitably modifying the dimensions of the plate portions (such as, for example, the plate portions IOC and/or 12C of Fig. 1 or 40C and/or 42C of Fig. 2). It is also possible to modify the lumped conductance of differently dimensioned sensors by modifying the total length ( and/or other dimensions) of the coil portions of the sensor (such as, for example, the coil portions 10A and/or 12A of Fig. 1 or the coil portions 40A and/or 42A of Fig. 2). It will be appreciated by those skilled in the art that any combination of the modifications of the coil portions and/or plate portions may be used to modify the sensor's lumped capacitance and/or lumped inductance). It is also noted that differences in dimensions of any of the plate portions and/or coil portions of the sensors may also modify the electrical lumped resistance of the sensors, which may need to be taken into account in the sensor design and implementation.

In, accordance with yet another embodiment of the sensor system, the electrical parameters of the RLC circuits of the sensors may be changed by changing the spacing ( distance or separation) between the coil portions 40 A and 42 A to change the lumped inductance of the RLC circuit, and/or by changing the spacing (distance or separation) between the plate portions 40C and 42C to change the sensor's lumped capacitance, or by changing in this way both the lumped capacitance and the lumped inductance of the RLC circuit of the sensor.

Any other suitable methods or means known in the art may be used to modify any of the electrically conductive or non-electrically conductive components of the sensors in order to achieve a change in the RLC circuit properties that will result in the resonance frequency range of each sensor not overlapping with the resonance frequency range of any other sensor of the group of sensors over the expected span of the measured parameter range in the measurement environment.

This embodiment, in which each sensor is different from the other sensors in the sensor group by being differently structured or internally modified is well suited to implement a sensor system in which each sensor will resonate in a range of frequencies which does not overlap with the range of resonance frequencies of any other sensor of the sensor system. Thus, the actual resonance frequency determined for any sensor in the sensor group (or sensor array), not only represents the value of the measured parameter as sensed by the sensor but is also sufficient for uniquely and distinctly determining which sensor in the array was the source of the measured resonance frequency. It is noted that while the embodiment described hereinabove provides a viable solution to the problem of sensor's signal identification, is has some drawbacks, in that it necessitates fabricating sets of differently structured sensors, which may make this approach more expensive than if one could use the same structure and dimensions in all the sensors of the array or group. Additionally, sensors having different dimensions may be difficult to use due to such sensors having different response curves which may make ir quite complicated to interpret the results from each sensor.

Therefore, another embodiment of the sensor systems of the present application makes use of identical sensors (or sensors which are similar within practical manufacturing tolerances), and changes the electrical parameter(s) of the sensors' RLC circuits by adjusting or tuning each sensor through the use an additional electrical component which is suitably electrically coupled to each sensor (or to most sensors, since there is at least one sensor in each sensor group of this embodiment that may not need such an electrical component for adjusting or tuning the RLC electrical properties thereof).

It is noted that the specific arrangement of the components of the reading unit 60 of the system 50A is not obligatory and other types of implementations are possible ( see for example the implementation illustrated in Fig. 4 below).

Reference is now made to Fig. 4 which is a schematic diagram illustrating a group of sensors connected in parallel to a sensor reading circuit in accordance with another embodiment of the sensor systems of the present application. The sensor system 50B is similar to the sensor system 50A of Fig. 3 except that the arrangement of the components of the reading unit 60B is different than their arrangement of the components of reading unit 60A (of Fig. 3). In the reading unit 60B, the response reading unit 64 is connected to the circuit at reading points 57 A and 7B. In this arrangement, the signal read by response reading unit 64 represents the voltage difference between the points 57 A and 57B.

Returning to Fig. 3, in the reading unit 60 A, the response reading unit 64 is connected across the terminals of the resistor RM. In this configuration, the voltage signal read by the response reading unit 64 represents the current flowing through the resistor RM. It is noted that both configurations are usable in determining the resonance frequencies of the sensors SI, S2, SN and the choice of the configuration of the reading unit circuit of the sensor system depends, inter alia, on the electrical resistance of the sensors SI, S2, .... , SN (represented schematically be Rl, R2, ... , RN , respectively ), on the resistance of the resistor RM, and may also depend on other electrical parameters of the sensors SI, S2, .... , SN.

Reference is now made to Figs. 5-8. Figs 5 and 6 are schematic diagrams illustrating sensor arrays having a plurality of sensors and a plurality of tuning capacitors, in accordance with another embodiment of the sensor arrays of the present application. Figs. 7 and 8 are schematic diagrams illustrating sensor arrays having a plurality of sensors and a plurality of tuning inductors, in accordance with yet another embodiment of the sensor arrays of the present application.

Turning to Fig. 5, the sensor system 90A includes the a reading unit 60A electrically coupled to a group of N sensors SI, S2, .... , SN trough a single pair of electrical conductors 52 and 54. The Sensors SI, S2, .... , SN are identical sensors (within manufacturing tolerances). Each of the sensors SI , S2, .... , SN may be electrically coupled to a tuning capacitor CE 1 , CE2, .... , CEN, respectively, as illustrated in detail in Fig. 7. In accordance with one implementation of the embodiment illustrated in Fig. 7, the tuning capacitors may be variable capacitors (such as, inter-digitating plate capacitors, or any other type of suitable variable capacitive element known in the art). The variable capacitors CE1, CE2, .... , CEN may be tuned in order to effectively change the capacitance of the RLC circuit of each of the sensors S I, S2, .... , SN such that each sensor will resonate in a range of frequencies which does not overlap with the range of resonance frequencies of any other sensor of the sensor system 90A over the entire expected range of values of the parameter to be measured in the measurement environment. This embodiment may be preferred in sensor systems and arrays having a relatively small number of sensors or in sensor systems and arrays having sensors of relatively large dimensions where the size of the tuning variable capacitor is not particularly critical.

In accordance with another implementation of the embodiment illustrated in Fig. 5, the tuning capacitors CE1, CE2, .... , CEN may be laser trimmable capacitors as is well known in the art. The trimmable capacitors CE1, CE2, .... , CEN may be trimmed in order to effectively change the capacitance of the RLC circuit of each of the sensors such that each sensor will resonate in a range of frequencies which does not overlap with the range of resonance frequencies of any other sensor of the sensor system 90A over the entire expected range of values of the parameter to be measured in the measurement environment. This embodiment may have the advantage that the capacitors CE1, CE2, .... , CEN may be automatically trimmed using laser trimming directly applied to the sensor array which may advantageously simplify and streamline the tuning process (especially if the number N of sensors in the array is large and the sensors are of small dimensions (for example, in the case of two dimensional micro-sensor arrays, fabricated using lithography type technology and the like).

In accordance with yet another implementation of the embodiment illustrated in Fig.

5, the tuning capacitors CE1, CE2,.... , CEN may be fixed value capacitors as is well known in the art. The capacitance of each of the fixed value capacitors CE1, CE2,.... , CEN may be preselected in order to effectively change the capacitance of the RLC circuit of each of the sensors such that each sensor will resonate in a range of frequencies which does not overlap with the range of resonance frequencies of any other sensor of the sensor system 90A over the entire expected range of values of the parameter to be measured in the measurement environment.

It will be appreciated by those skilled in the art that the number of the tuning capacitors need not be equal to the number of sensors in the array. For example, one may modify the circuit illustrated in Fig. 5 such that one sensor of the array does not have a tuning capacitor connected thereto, while all the other remaining sensors may each have a tuning capacitor connected thereto.

Turning to Fig. 6, the sensor system 90B is similar to the sensor system 90A (of Fig. 5) except the system 90B includes the reading unit 60B (of Fig.4) instead of the reading unit 60 A (of Fig. 5). All other components of the system 90B are identical to those of System 90A (of Fig. 5). The tuning procedure of the sensors of the sensor system 90B and the different embodiments with respect to the various implementations of the tuning capacitors CE1, CE2,.... , CEN are as disclosed in detail hereinabove for the system 90 A of Fig. 5.

Turning to Fig. 7, the sensor system 100A includes the a reading unit 60A electrically coupled to a group of N sensors SI, S2, .... , SN trough a single pair of electrical conductors 52 and 54. The Sensors SI, S2, .... , SN are identical sensors (within manufacturing tolerances). Each of the sensors SI, S2, .... , SN may be electrically coupled to a tuning inductor LEI, LE2,... , .LEN, respectively, as illustrated in detail in Fig. 7. In accordance with one implementation of the embodiment illustrated in Fig. 7, the tuning inductors may be variable inductors (such as, for example, coils with a variable position ferrite core, or any other type of suitable variable inductive element known in the art). The variable inductors LEI, LE2, .... , LEN, may be tuned in order to effectively change the inductance of the RLC circuit of each of the sensors SI, S2, .... , SN such that each sensor will resonate in a range of frequencies which does not overlap with the range of resonance frequencies of any other sensor of the sensor system 100A. This embodiment may be preferred in sensor systems and sensor arrays having a relatively small number of sensors or in sensor systems and sensor arrays having sensors of relatively large dimensions where the size of the tuning variable inductor is not particularly critical.

In accordance with another implementation of the embodiment illustrated in Fig. 7, the tuning inductors LEI, LE2, .... , LEN may be fixed value inductors (such as, for example, inductive coils, ferrite core coils, and the like, as is well known in the art). The inductance of each of the fixed value inductors LEI, LE2,....LEN, may be selected in order to effectively change the inductance of the RLC circuit of each of the sensors such that each sensor will resonate in a range of frequencies which does not overlap with the range of resonance frequencies of any other sensor of the sensor system 100 A over the entire expected range of values of the parameter to be measured in the measurement environment.

It will be appreciated by those skilled in the art that the number of the tuning inductors need not be equal to the number of sensors in the array. For example, one may modify the circuit illustrated in Fig. 9 such that one sensor of the array does not have a tuning inductor connected thereto, while all the other remaining sensors of the array may each have a tuning inductor connected thereto.

Turning to Fig. 8, the Sensor system 100B is similar to the sensor system 100A (of Fig. 7) except the system 100B includes the reading unit 60B (of Fig.4) instead of the reading unit 60A (of Fig. 7). All other components of the system 100B are identical to those of System 100A (of Fig. 7). The tuning procedure of the sensors of the sensor system 100B and the different embodiments with respect to the various implementations of the tuning inductors LEI, LE2, .... , LEN are as disclosed in detail hereinabove for the System 100A of Fig. 7.

It is noted that while the embodiments having identical tuning electrical components such as the tuning capacitors and tuning inductors are quite convenient to implement, other embodiments of the sensor systems may include sensors which are connected to no tuning electrical component or to more than one tuning electrical component. For example, a sensor array may be constructed in which one sensor has no tuning electrical components connected thereto, a second sensor having only a tuning capacitor connected thereto, a third sensor having a tuning inductor connected thereto and a fourth sensor having a tuning inductor and a tuning capacitor connected thereto.. Such combinations and permutations of the tuning components may allow more flexibility in tuning the resonance frequency ranges of the sensors such that they do not overlap over the expected range of values of the physical parameter in the measurement environment. Practically, any combination of the above tuning electrical components may be used and connected to the sensors (including the possibility of no tuning component being connected to a sensor) in the sensor arrays of the present application.

It will be appreciated by those skilled in the art that it may be possible to use any possible combination of the embodiments of the sensors in order to implement the novel sensor arrays disclosed herein. For example, in accordance with one embodiment of the sensor system, the system may include sensors having identical external dimensions (within practical manufacturing tolerances) in which the sensors' electrical RLC properties are different by using a different layout of the coil portions and/or plate portions of the sensors.

In accordance with another embodiment of the system, the system may include sensors having different external dimensions in which the sensors electrical RLC properties are different by using a different layout of the coil portions and/or plate portions.

In accordance with another embodiment of the system, the system may include some sensors having identical external dimensions (within practical manufacturing tolerances) in which the sensors' electrical RLC properties are different by using a different layout of the coil portions and/or plate portions of the sensors, and some sensors having different external dimensions in which the sensors electrical RLC properties are different by using a different layout of the coil portions and/or plate portions. The sensors are selected such that the resonance frequency range of each sensor does not overlap with the resonance frequency range of any other sensor of the plurality of sensors over the expected span of the measured parameter range in the measurement environment.

In accordance with another embodiment of the system, the system may include some sensors having identical external dimensions (within practical manufacturing tolerances) in which the sensors' electrical RLC properties are different by using a different layout of the coil portions and/or plate portions of the sensors, and some sensors having an additional tuning capacitor and/or an additional tuning inductor and/or an additional tuning resistor (in any possible configuration disclosed hereinabove and illustrated in Figs. 5-10) . The sensors are selected such that the resonance frequency range of each sensor does not overlap with the resonance frequency range of any other sensor of the plurality of sensors over the expected span of the measured parameter range in the measurement environment.

It is noted that any type or mix of types of sensors may be used to implement the sensor systems of the present application as long as all the sensors that are read using a single pair of electrical conductors are selected such that the resonance frequency range of each sensor does not overlap with the resonance frequency range of any other sensor of the plurality of sensors over the expected span of the measured parameter range in the measurement environment.

For example in another embodiment of the sensor arrays, the sensor array may include sensors for measuring different parameters which may be connected in parallel to the electrical conductors. Such an embodiment may include but is not limited to an array including sensors for measuring pressure and sensors for measuring strain. As long as the resonance frequency range of each of these different types of sensors does not overlap with any other sensor in the array over the expected range of values of both the strain and the pressure in the measurement environment, such mixed sensor arrays may successfully be read using a suitable exciting and reading unit electrically coupled to all the sensors of the array as explained in detail hereinabove, since each of the sensors has its uniquely identifiable electrical resonance frequency range.

Practically, the maximum number of sensor that may connected in parallel to a single pair of wires (such as, for example the wires 52 and 54 of Fig. 3) is determined, inter alia, by the frequency separation between the range of resonance frequencies of each individual sensor and the entire frequency bandwidth available for being read by the electronics of the reading unit (such as, for example the reading units 60A and 60B of Figs 1-8). The frequency separation depends, among others, on the Q value of the electrical resonators (how sharp are the frequency peaks), how much does the frequency change when the sensors are measuring the span of parameters they should be measuring in the measurement environment, the detection method, the time available for sampling and the resolution that is required for the measurements. By calculating, or simulating, the frequency response of the whole RLC circuit, one can determine the frequency response over the full range of the measured parameters and the circuit Q and adjust or select the tuning component values to achieve the required separation.

It is therefore to be expected that for sensor systems and/or sensor arrays having a very large number of sensors it may not always be practically possible to read all the sensors in the system by connecting all of the sensors in parallel to a single pair of electrical conductors ( as shown in Figs. 3 and 4) due to limitations in the total frequency bandwidth of the system circuit or the time required to scan the bandwidth or due to the necessity to allocate a large resonance frequency range window to each sensor because of a wide range of variation in the values of the parameter in the measurement environment.

In such cases another embodiment of the sensor systems and/or sensor arrays of the present application contemplates the use of several pairs of electrical conductors, with a first group of sensors connected in parallel to a first pair of electrical conductors, a second group of sensors connected in parallel to a second pair of electrical conductors, a third group of sensors connected in parallel to a third pair of electrical conductors, and so forth. In such an embodiment, the number of sensors connected to each pair of wires may be equal or may be different. In such systems, each of the sensors in a group of sensors that are connected in parallel to one pair of wires are selected such that the resonance frequency range of each sensor does not overlap with the resonance frequency range of any other sensor of the plurality of sensors over the expected span of the measured parameter range in the measurement environment. However, two ( or more) sensors belonging to different sensor groups connected to different wire pairs may have either identical or overlapping resonance frequency ranges as they are not being read simultaneously by the same reading circuit.

Reference is now made to Figs. 9 and 10 which are schematic block diagrams illustrating two different systems of sensors having multiple sensor groups electrically connected to multiple wire pairs, in accordance with two additional embodiments of the sensor systems and sensor arrays of the present application.

Turning to Fig. 9, the multi group system 110 includes a sensor array including N x M sensors ( which may preferably, but not obligatorily be arranged in N rows and M columns) and M pairs of electrical conductors. The sensors of a first row of sensors S l l , S12, ... S IN are connected in parallel to a first circuit reading unit CRU1 using a first pair of electrical conductors ECl . The sensors of a second row of sensors S21, S22, .... , S2N are connected in parallel to a second circuit reading unit CRU2 using a second pair of electrical conductors EC2. The sensors of the M'th row of sensors SMI, SM2, ... , SMN are connected in parallel to an M'th circuit reading unit CRUM using an M'th pair of electrical conductors ECM. The sensors of the system 110 may be implemented as any type of sensors disclosed in the present application and the system 110 may use any combination of any of the different sensor types disclosed in the present application. It is noted that while the sensors of the system 1 10 are schematically illustrated as arranged in a rectangular array, this is not obligatory and the sensor of the system 1 10 may be arranged in any type of desired two dimensional or three dimensional arrangement by suitably modifying the arrangement and/or the dimensions of one or more of the M pairs of electrical conductors ECl , EC2, ... , ECM , if needed. Therefore, the system 1 10 is not limited to using flat or planar two dimensional sensor arrays and may include any desired linear or two dimensional or three dimensional sensor array configurations.

The sensors of each row of the M rows of sensors are selected such that each sensor in the row will resonate in a range of frequencies which does not overlap with the range of resonance frequencies of any other sensor of the same row of sensors over the entire expected range of values of the measured parameter in the measurement environment. However, since each row of sensors of the M rows in the system 110 is excited and read by a dedicated circuit reading unit, some or all of the resonance frequency ranges of sensors in any row may be duplicated in the sensors of the other rows. Thus, instead of requiring M x N sensors having different non-overlapping resonance frequency ranges, the arrangement of the system 110 requires using only N sensors having different non-overlapping resonance frequency ranges advantageously reducing the number of sensors that are required to have non-overlapping resonance frequency ranges.

All M circuit reading units CRU1, CRU2, .... , CRUM are electrically connected to a Processor/controller unit 115. The reading units CRU1, CRU2, .... , CRUM may be implemented as shown for the reading units 60A and/or 60B disclosed in detail hereinabove. The processor/controller unit 115 may be used to control the operation of the reading units CRU1, CRU2, .... , CRUM and to acquire and/or process the signals received from the sensors connected to each of the reading units CRU1, CRU2, .... , CRUM in order to determine the values of the measured parameters for each sensor by determining the resonance frequencies of the sensors and the corresponding values of the measured parameter for each sensor, as disclosed in detail hereinabove. The processor/controller unit may be any type of processing unit and/or controlling unit known in the art, including but not limited to, a computer, a minicomputer, a processor, a microprocessor, a laptop computer, a tablet computer, a digital signal processor, and the like. The processor/controller unit 115 may also include suitable data storage devices such as memory units and/or any type of magnetic storage or optical storage units or semiconductor based storage units known in the art. The processing /controlling unit 115 may also include any type of user interface device for accepting user input, such as but not limited to a keyboard, a mouse, a pointing device, a touch screen, and the like and also a display device (such as, but not limited to a display screen, a touch screen and the like) for displaying data to the user of the system 110.

Turning to Fig. 10, the multi group system 120 includes a sensor array including N x M sensors (which may preferably, but not obligatorily be arranged in N rows and M columns) and M pairs of electrical conductors. The sensors of a first row of sensors SI 1 , S12, ... SIN are connected in parallel to a first pair of electrical conductors ECl. The sensors of a second row of sensors S21, S22, .... , S2N are connected in parallel to a second pair of electrical conductors EC2. The sensors of the M'th row of sensors SMI, SM2, ... , SMN are connected in parallel to an M'th pair of electrical conductors ECM. The sensors of each individual row of the M rows of sensors are connectable to a circuit reading unit (CRU) 125 by a multiplexer unit (MUX) 123. The Multiplexer unit 123 is electrically connected to all M pairs of electrical conductors ECl, EC2, ... , ECM. The Multiplexer unit 123 is electrically connected to the circuit reading unit 125. The circuit reading unit 125 is electrically connected to a processor/controller unit 115 which may control the operation of the circuit reading unit 125 and which may acquire and/or store and/or process data received from the circuit reading unit 125 to obtain the value of the parameter sensed by any of the sensors included in the system 120. The processor/controller unit 115 may also be electrically connected to the multiplexer unit 123 for controlling the operation of the multiplexer 123. However, in accordance with another embodiment of the system 120, the multiplexer unit 123 may be directly controlled by the circuit reading unit 125 ( which in turn may be controlled by the processor/ controller unit 115, obviating the need for the electrical connection between the multiplexer unit 123 and the processor/controller unit).

The sensors of the system 120 may be implemented as any type of sensors disclosed in the present application and the system 120 may use any combination of any of the different sensor types disclosed in the present application. It is noted that while the sensors of the system 120 are schematically illustrated as arranged in a rectangular array, this is not obligatory and the sensor of the system 120 may be arranged in any type of desired two dimensional or three dimensional arrangement by suitably modifying the arrangement and/or the dimensions of one or more of the M pairs of electrical conductors ECl, EC2, ... , ECM, if needed. Therefore, the system 120 is not limited to using flat or planar two dimensional sensor arrays and may include any desired linear or two dimensional or three dimensional sensor array configurations.

The sensors of each row of the M rows of sensors are selected such that each sensor in the row will resonate in a range of frequencies which does not overlap with the range of resonance frequencies of any other sensor of the same row of sensors over the entire expected range of values of the measured parameter in the measurement environment. However, since each row of sensors of the M rows in the system 120 is excited and read individually by the circuit reading unit 125 (such that at any time during the operation of the system only a single row of sensors is operationally electrically coupled to the circuit reading unit 125 due to the action of the multiplexer 123), some or all of the resonance frequency ranges of sensors in any row may be duplicated in the sensors of the other rows. Thus, instead of requiring M x N sensors having different non-overlapping resonance frequency ranges, the arrangement of the system 110 requires using only N sensors having different non-overlapping resonance frequency ranges advantageously reducing the number of sensors that are required to have non-overlapping resonance frequency ranges.

The reading unit 125 may be implemented as shown for the reading units 60A and/or 60B disclosed in detail hereinabove. The processor/controller unit 115 may be used to control the operation of the reading unit 125 and to acquire and/or process the signals received from the sensors connected thereto in order to determine the values of the measured parameters for each sensor by determining the resonance frequencies of the sensors and the corresponding values of the measured parameter for each sensor, as disclosed in detail hereinabove. The processor/controller unit 115 may be any type of processing unit and/or controlling unit known in the art, including but not limited to, a computer, a minicomputer, a processor, a microprocessor, a laptop computer, a tablet computer, a digital signal processor, and the like. The processor/controller unit 115 may also include suitable data storage devices such as memory units and/or any type of magnetic storage or optical storage units, or semiconductor based storage units known in the art. The processing /controlling unit 115 may also include any type of user interface device for accepting user input, such as but not limited to a keyboard, a mouse, a pointing device, a touch screen, and the like and also a display device (such as, but not limited to a display screen, a touch screen and the like) for displaying data to the user of the system 120. An advantage of the system 120 as compared to the system 110 is that only a single circuit reading unit 125 is used in the system 120 as compared to M circuit reading units implemented in the system 110. While the System 120 also requires a multiplexer unit 123 in order to select which row of sensor is to be electrically coupled to the circuit reading unit 125, this may still result in a substantial saving of components making the system 120 simpler to construct and less costly. However, as will be appreciated by those skilled in the art, in the system 120 the sensor rows are sequentially read one after the other so the time points at which each row of sensors are read are not identical. Nevertheless, if the parameter to be measured in the measurement environment does not change very rapidly (relative to the time required for all sensor rows to be read), this type of sequential reading may be tolerated.

In cases where the parameter to be measured varies rapidly, the system 110 may be preferred as it may allow simultaneous reading of all sensor rows at the same time. However, the system 110 may need to be modified by including a memory buffer (not shown in Fig. 1 1) in order to allow very fast reading of the signal received from the rows of sensors and storage of the signal in the memory buffer of each of the circuit reading units CRU1, CRU2, ... , CRUM ( by digitizing the signal and storing the digitized signal in the buffer memory. The memory buffers may then be sequentially send as output into the processor/controller 1 15 which may process the data and determine the value of the parameter to be measured for each sensor of the system 120. While such sequential data reading from the buffer memory of each of the circuit reading units CRU1 , CRU2, ... , CRUM and the sequential processing of the data may require a discrete amount of time ( depending inter alia, on the speed of data acquisition and the speed of processing by the processor, controller unit 115, it still has the advantage that all the parameter values computed for all of the sensors of the system 120 represent simultaneously sensed values of the measured parameter.

In order to test the feasibility of the tuned sensor systems and sensor arrays disclosed herein, the inventor has performed simulations of several examples of such tuned arrays using the simulation program software LT Spice Version 4.13n, commercially available from Linear Technology Corporation, U.S.A. In addition to the simulations, the inventor also constructed a simple prototype of a sensor array including two pressure sensors electrically connected in parallel to a single pair of electrically insulated wires and successfully determined the resonance frequency of both sensors by using the chirp signal application method and analysis method as disclosed in the present application.

Reference is now made to Figs. 11-14. Fig. 11 is a schematic diagram illustrating a three sensor array system circuit simulated by the SPICE LT program. Fig. 12 is a schematic graph illustrating the simulated response of the circuit of Fig. 11 to a chirp signal. Fig. 13 is a schematic graph illustrating the details of part of the graph of Fig. 12. Fig. 14 is a schematic graph illustrating part of the FFT of the simulated response of Fig. 12.

Turning to Fig. 11, the simulated circuit includes the inductor LI (having an inductance of ΙμΗ) and the capacitor C2 (having a capacitance of 10 nF) representing a first sensor, the inductor L2 (having an inductance of ΙμΗ) and the capacitor C3 (having a capacitance of 15 nF) representing a second sensor and the inductor L3 (having an inductance of ΙμΗ) and the capacitor C4 (having a capacitance of 20 nF) representing a third sensor. The resistor R3 has a resistance of 1 Ω. The simulation program simulated the results of feeding a chirp electrical signal to the circuit and simulating the voltage across the resistor R3 as a function of time. The chirp signal in the simulation has an amplitude of IV and a frequency span of 0 - 2MHz in a time period of 1 millisecond.

Turning to Figs. 12-13, the vertical axes of Figs 12-13 represent the simulated voltage between the resistor R3 and ground (of Fig. 11) and the horizontal axes of Figs 12-13 represent time in milliseconds. The curve 140 represents the voltage between the resistor R3 (of Fig. 11) and ground. Each of the three spaced apart minima points 141, 142 and 143 of the curve 140 correlates to time points at which one of the three simulated sensors is at resonance, since at that time, the chirp frequency correlates to that sensor's resonance frequency, which results in a minimum voltage on the resistor R3. The details of the voltage curve 140 may be seen in Fig. 13.

Turning to Fig. 14, the curve 160 represents a portion of the simulated Fast Fourrier transform (FFT) of the voltage curve 140 of Fig. 12. The vertical axis of Fig. 14 represents signal amplitude (in decibels) and the horizontal axis of Fig. 14 is the signal frequency in Hz on a logarithmic scale. The three points 161, 162 and 163 of the curve 160 represent the resonance frequencies of each of the three sensors of the circuit of Fig. 11.

Reference is now made to Figs. 15-19. Fig. 15 is a schematic diagram illustrating a three sensor array system circuit simulated by the SPICE LT program. Fig. 16 is a schematic graph illustrating the simulated response of the simulated circuit of Fig. 15 to a rising voltage step signal. Fig. 17 is a schematic graph illustrating the details of part of the graph of Fig. 16 on an expanded time scale. Fig. 18 is a schematic graph illustrating part of the simulated FFT of the simulated response of Fig. 16 on an expanded frequency scale. Fig. 19 is a schematic graph illustrating part of the simulated FFT curve of Fig. 18 on an expanded scale.

Turning to Fig. 15, the simulated circuit includes the inductor LI (having an inductance of ΙμΗ) and the capacitor C2 (having a capacitance of 10 nF) representing a first sensor, the inductor L2 ( having an inductance of ΙμΗ) and the capacitor C3 (having a capacitance of 15 nF) representing a second sensor and the inductor L3 (having an inductance of ΙμΗ) and the capacitor C4 (having a capacitance of 20 nF) representing a third sensor. The resistor R3 is a series resistor having a resistance of 1 Ω. The simulation program simulated the results of feeding a 5V rising step electrical signal to the circuit and simulating the voltage on the resistor R3 as a function of time.

Turning to Figs. 16-17, the vertical axes of Figs 16-17 represent the simulated voltage on the resistor R3 of Fig. 15 and the horizontal axes of Figs. 16-17 represent time in milliseconds. The curve 180 represents the voltage on the resistor R3 (of Fig. 15).

Turning to Figs. 18-19, the curve 200 represents a portion of the simulated Fast Fourier transform (FFT) of the voltage curve 180 of Fig. 16. The vertical axes of Figs. 18-19 represent signal amplitude (in decibels) and the horizontal axes of Figs. 18-19 represent the signal frequency in Hz on a logarithmic scale. The three points 201, 202 and 203 of the FFT curve 200 are associated with the resonance frequencies of each of the three sensors of the circuit of Fig. 15.

Reference is now made to Figs. 20-23. Fig. 20 is a schematic diagram illustrating a three sensor array system circuit simulated by the SPICE LT program. Fig. 21 is a graph illustrating the simulated response of the circuit of Fig. 20 to a square pulse signal. Fig. 22 is a schematic graph illustrating the details of part of the graph of Fig. 21. Fig. 23 is a schematic graph illustrating part of the FFT of the simulated response of Fig. 21.

Turning to Fig. 20, the simulated circuit includes the inductor LI (having an inductance of ΙμΗ) and the capacitor C2 (having a capacitance of 10 nF) representing a first sensor, the inductor L2 ( having an inductance of ΙμΗ) and the capacitor C3 (having a capacitance of 15 nF) representing a second sensor and the inductor L3 (having an inductance of ΙμΗ) and the capacitor C4 (having a capacitance of 20 nF) representing a thir4d sensor. The series resistor R3 has a resistance of 1 Ω. The simulation program simulated the results of feeding a IV chirp electrical signal with a frequency span from 0 to 2MHz within 1 milUsecond to the circuit and simulated the voltage on the resistor R3 as a function of time.

Turning to Figs. 21-22, the vertical axes of Figs 21-22 represent the simulated voltage on the resistor R3 of Fig. 20 and the horizontal axis of Fig 21 represents time in milliseconds and the horizontal axis of Fig. 22 represents time in microseconds. The curve 210 represents the simulated voltage on the resistor R3 (of Fig. 20).

Turning to Fig. 23, the curve 240 represents a portion of the simulated Fast Fourrier transform (FFT) of the voltage curve 210 of Fig. 21. The vertical axis of Fig. 23 represents signal amplitude (in decibels) and the horizontal axis of Fig. 23 represents the signal frequency in Hz on a logarithmic scale. The three points 241, 242 and 243 of the curve 240 represent the minima associated with the resonance frequencies of each of the three sensors of the circuit of Fig. 20.

It will be appreciated by those skilled in the art that the above simulations indicate that as long as the resonance frequencies of each of the three sensors in any one of the above simulations do not overlap, it is possible to attribute each of the frequency minimum points in the FFT curves ( such as the points 161, 162 and 163 of Fig. 14 or the points 201, 202 and 203 of Fig. 19 or points 241, 242 and 243 of Fig. 23) to a particular sensor in the circuit (based on the pre-known resonance frequency range of each of the sensors in the circuit).

Thus, when the actual sensors of the systems of the present application are constructed each sensor may be constructed (and/or tuned) such that within the entire expected range of the values of the parameter(s) to be measured in the measurement environment, the electrical resonance frequency ranges of each of the sensors do not overlap, which enables to clearly identify the sensor responsible to each and every measured or computed resonance frequency (detected within the relevant frequency range of the frequency domain FFT curve). Thus, by appropriate tuning of the sensors, it is known before the measurement is performed which resonance frequency belongs to which sensor enabling identification by the particular resonance frequency as determined from the response of the sensor array to the electrical excitation signal.

After determining the frequencies of the minimum values that are associated with each of the sensors in the sensor array, the values of the measured parameter for the sensors is calculated by using a calibration curve for sensors in the array or a function describing the calibration curve of the sensors, or by using a look-up table associate with the sensors or by using an empiric calibration function. This calculation is typically needed because the sensor's resonance frequency is not always a linear function of the value of the measured parameter.

It will be appreciated by those skilled in the art that the wiring connecting the sensors of the sensor array to the measurement equipment and the environment in which the array and the wires are positioned in, may induce parasitic inductance and capacitance of varying values that may offset the reading. To overcome this problem, an additional reference sensor may be added to the sensor array or to the sensor system. Such a reference sensor is constructed or assembled so that it is isolated from the physical parameter of interest. By comparing the determined resonance frequency of this sensor when the sensor array is in a non controlled environment to it's resonance frequency in a controlled environment, in is possible to find and model parameters that may be used to correct the readings of the other sensors in the sensor array. Also, in some applications where the environmental temperature may change the readings (i.e. change in the internal pressure of a pressure sensor resulting from the temperature change), one or more temperature sensing elements may be installed near to the sensors of the array and their readings may be used to compensate for temperature effects. One or more reference sensors, if they have the same temperature sensitivity as the actual sensors exposed to the measurement environment and are at the same temperature, may also be used to compensate for temperature effects.

Thus, the sensor arrays of the systems disclosed herein may also include one or more compensating sensors for compensating for variations in temperature variations in the measurement environment or even for compensating for temperature variations from one sensor to another sensor (this may be particularly important in sensor systems in which the individual sensors are physically separated from each other by a substantial distance, where significant temperature variations may occur for different sensors of the system) It is noted that while such compensating sensors may be read by their own dedicated reading circuits (for example, if the sensors are pressure sensors, one or more temperature sensors, such as, for example, thermistors, may be used and may be separately connected to and read by the processor/controller unit 115 using dedicated reading electrical conductors.

However, in cases in which a large number of such compensating sensors is used, it may be advantageous to use compensating sensors that are by themselves RLC type electrically resonating sensors whose resonance frequency varies as a function of temperature (or other parameter to be compensated for) but not as a function of the pressure (or any other parameter to be measured). In such a case, the compensating temperature sensors (or any other type of different compensating sensor being used) may be also connected in parallel to the same pair of electrical conductors connecting all the pressure sensors of the sensor group or sensor row. In such a case it is necessary to select (or tune) the temperature (or other parameter) compensating sensors such that their range of resonance frequencies will not overlap with the range of resonance frequencies of any other sensor (including pressure sensors and temperature sensors) connected in parallel to the same pair of electrical conductors, in order to be able to uniquely identify each of the sensors by it's specifically associated range of resonance frequencies as explained in detail hereinabove.

It is noted that in accordance with additional embodiments of the sensor arrays and sensor systems of the present application the sensors of the sensor arrays may be arranged and/or constructed and/or assembled in three different arrangements or configurations: in a first configuration each compensated sensor includes a reference sensor therein. In a second configuration the sensor array includes one reference sensor and each of the compensated sensors is compensated using compensating data obtained from the single reference sensor of the sensor array. In a third configuration, the compensated sensors are grouped into N sensor groups, each compensated sensor group is a associated with a single reference sensor selected from N reference sensors included in the sensor array such that each of the sensors in a sensor group is compensated by data from the single reference sensor associated with that sensor group.

While this type of compensated sensor array requires additional sensors to sense the parameters to be compensated for, it reduces on the total number of electrical conductor pairs required in the system by connecting the compensating sensors in parallel to the same pair of wires that are used for connecting the pressure sensors. Alternatively, in accordance with yet another embodiment of the sensor systems of the present application, the system may include compensating sensors (reference sensors) which are not RLC type electrically resonating sensors. In such an embodiment the output of the non-RLC type reference sensors may be separately read through electrical conductors different from the pair of electrical conductors used for reading the output of the RLC type sensors. The output from the reference sensors may then be used for adjusting or correcting the readings of the RLC type sensors of the array.

It is noted that the sensors, system and methods disclosed herein are not limited to measuring pressure and may be applied to any type of sensor array, sensor system for measuring any parameter in a measurement environment as long as the sensors are using an electrically resonating circuit having a resonance frequency that is a function of the value of the measured parameter in the measurement environment.

Reference is now made to Fig. 24 which is a schematic block diagram illustrating the steps of a method for operating a sensor array in a measurement environment in accordance with an embodiment of the methods of the present application.

The method includes providing a tuned sensor array (Step 300) as disclosed hereinabove and illustrated in the drawings. The tuned sensor array may be a single sensor array (such as , for example the sensor arrays disclosed in Figs 3-8) or a sensor array having multiple sensor arrays (Such as any single sensor group electrically connected in parallel to a pair of electrical conductors, such as any of the individual groups of sensors electrically connected in parallel to any of the pairs of electrical conductors ECl, EC2,..., ECM of Figs. 9 and 10).

The sensor array is then placed or positioned in the measurement environment (step 302). The measurement environment may be any type of measurement environment know in the art, such as but not limited to an industrial measurement environment ( such as , for example a hydraulic system, a chemical reactor and the like), a medical measurement environment, a human or an animal body, a patient organ or body cavity or blood vessel, and the like. The sensor arrays of the present application may be adapted for use in any type of measurement environment. An exciting electrical signal is then applied to the sensor array through the electrical conductors connecting the individual sensors and the arrays response is sensed (step 304). The exciting electrical signal may be a chirp signal having a frequency range spanning the entire range of resonance frequencies of all the sensors of the sensor array over the entire range of the measured parameter's values that need to be determined in the measurement environment. The chirp may be a constant amplitude chirp or a variable amplitude chirp. The chirp signal may have a frequency that varies linearly with time or may have a frequency that varies non-linearly with time. Any combination of the above indicated types of a chirp signals may be used (including, for example, a constant amplitude chirp having a frequency that varies linearly with time, a variable amplitude chirp having a frequency that varies linearly with time, a constant amplitude chirp having a frequency that varies non- linearly with time and a variable amplitude chirp having a frequency that varies non-linearly with time). The exciting signal may also be a square wave electrical signal or a step electrical signal (both a rising step and a falling step signal may be used).

The sensing of the electrical response of the sensor array may be performed as disclosed hereinabove by measuring the current flowing in the circuit (represented by the voltage measured on a resistor, such as for example the resistor RM of Figs. 3, 5 and 7) or by measuring the voltage difference between the two electrical conductors (such as, for example, between the points 57A and 57B of Figs. 4, 6 and 8), depending on the configuration of the electrical circuit being used. The measured response of the sensor array may then be processed to obtain a set of frequencies at which there are amplitude minima associated with the resonance frequencies of each sensor of the sensor array (Step 306). The processing of the response may be performed in several different ways depending, inter alia, on the type of the exciting electrical signal applied to the sensor array). For example, when a chirp electrical signal is used as the exciting electrical signal, the sensed response will have a plurality of frequencies at which the amplitude of the response has minima. Since the parameters of the applied chirp are precisely known, the processing is done by determining the times at which the response amplitude reaches minimum values and determining from these time points the frequencies of the minimum points.

If the exciting electrical signal is a square wave signal or a step signal (either rising or falling step), the response signal is further processed by to perform a spectral analysis on the sensed signal. The spectral analysis may be performed using any spectral analysis method or algorithm know in the art, including but not limited to, a Fourier transform method, a wavelet based spectral analysis method, a multitaper spectral analysis method, a Pepisode spectral analysis method and a smooth periodogram method. However, any other type of spectral analysis method or algorithm known in the art may be used to perform the spectral analysis of the response signal of the sensor array. The results of the spectral analysis are processed to determine a plurality of frequencies at which the amplitude of the processed signal has minima points. For example, if the response signal is spectrally analyzed by subjecting it to a Fourier transform method, the resulting frequency domain representation will show a plurality of frequencies at which the amplitude has a minimum value (such as, for example, the frequencies of the minimum points 161, 162 and 163 of Fig. 14, or the frequencies of the points201, 202 and 203 of Fig. 18).

After the set of frequencies (at which there are amplitude minima in the response signal itself or in the results of the frequency domain spectral analysis obtained by processing the response signal) is determined, the value of the measured parameter is determined for each sensor of the sensor array from the determined set of frequencies (Step 308). As each frequency of the frequencies determined in step 306 is associated with the resonance frequency of a single sensor of the sensor array, the value of the measured parameter for the sensor may be determined by using a look up table (LUT) or by computing the value by using a suitable calibration function to compute a parameter each frequency value determined. Such an LUT or calibration function (Calibration curve) may be obtained by pre-calibrating the sensor array in a controlled environment in which the array is subjected to known values of the parameter to be measured and storing the LUT and/or computing a calibration function for further use during measurements, as is well known in the art.

In cases in which the measurement of the value of parameter to be determined may be affected by another parameter to be measured ( for example, pressure measurements may be affected by changes of the temperature in the measurement environment), there may be additional ( optional) steps of the method in which data about the temperature may be received from additional temperature sensor(s) in the array and a correction for temperature changes may be computed, The temperature Data may be received from non- electrically resonating temperature sensors of from electrically resonating temperature sensor. In such a case, the data from one or more temperature sensors may be acquired and a temperature correction may be applied to the values of the measured pressure to compensate for different temperature at different sensors or to correct the values of the parameter determined in Step 308 for all sensors of the array. Optionally, the sensors may be compensated sensors which the measured value of the pressure (or other parameter) is compensated by use of a reference sensor(s) in the array which provide an indication of the net effect of the change in the second parameter (such as, for example the temperature at the sensor) on the measured value of the first parameter (such as pressure). Such a reference sensor may be separate sensors included in the array or may be reference sensors included within each of the individual sensors.