| DE1112141B | 1961-08-03 | |||
| JPH04127306A | 1992-04-28 | |||
| JPH10268950A | 1998-10-09 | |||
| US20020190734A1 | 2002-12-19 |
| 1. | A converter for resistive sensors of high sensitivity comprising; • A voltage stabilizing IC of threeterminal, which have the input terminal provided by nonstabilized power through the converter's power terminal, the common terminal receiving resistance change and the output terminal in which the signal of the sensing resistor is changed into voltage to put out, Zener diode which is connected between the ICs output terminal and the converter's output terminal to put out it after the signal voltage is separated from the converted voltage of the output terminal ■ Two resistors connected between the ICs output terminal and common terminal, and between the ICs common terminal and ground terminal separately. Of the abovementioned two resistors, one resistor is a one which senses any physical variable and the other resistor is a one which sets up the DC stabilized voltage corresponding to the physical variable required. |
| 2. | The converter as claimed in claim 1 wherein the sensitive resistor is connected between the ICs common terminal and the ground terminal when having the positive sensing coefficient, and between the ICs output terminal and common terminal when having the negative sensing coefficient. |
| 3. | The converter as claimed in claim 1 wherein the minimum value of section measured is determined by the adjustment of the setting resistor of two resistors. |
| 4. | The converter as claimed in claim 1 wherein the minimum operating current of the relay in the physical value aimed is provided by the adjustment of the setting resistor of two resistors. |
| 5. | The converter as claimed in claim 1 wherein the stabilized DC power supply for the operating of the converter and the converting operation of signal are carried out by a voltage stabilizing IC of threeterminal simultaneously. |
| 6. | The converter as claimed in claim 1 wherein as the converter's output has current source or voltage source, it can put out the output voltage correctly without regarding magnitude of load in limit of maximum output current of Zener diode and the IC. |
| 7. | The converter as claimed in any one of the above claims wherein all the sensors which changes any physical variable into resistance can be used to the converter. |
Technical Field The present invention relates to a converter and more particularly to a converter for resistive sensors of high sensitivity.
Background of the Invention
A converter of bridge circuit is well known as a device of converting the sensitive resistance of physical variable into voltage.
Though a converter of bridge circuit is simple in its circuit, the stabilized power supply should be provided and the ampere meter of high sensitivity should be used in case high accuracy is required,.
And as the signal voltage or electric current in bridge circuit cannot drive directly such control elements as relay or control electrode of SCR, the amplifier of high input resistance or follower should be provided separately.
Because of these reasons, the converter for sensing resistance and FET amplifier of high input resistance or the sensing means coupled follower are developed and used. The smaller the signal is, the higher the amplification factor is, the higher accuracy is required, because of the various noises, distortion and the characteristic changes of the elements by circumstances in the circuits, the measures for its improvement are required, as a result, manufacturing expenses are greater. In addition, the displaying value of most measuring devices used the signal converter is started from the zero point, but practically in measuring of physical quantities of industrial fields it is convenient to display the values of available ranges among the total measuring ranges selectively.
These purposes are difficult to accomplish by only known converters of sensing signal, and can be carried out by the additional devices. This means that the devices would be expensive. The present invention is provided to solve these problems appeared in prior devices.
Summary of the Invention
The object of the present invention is to provide a simple converter of high sensitivity and power, and its utilization. For this, a converter for the sensitive resistor-voltage (electric current), namely the converter consists of a voltage stabilizing IC of three-terminal (hereinafter referred to as "IC"), which have the input terminal provided by non-stabilized power, the common terminal receiving resistance change and the output terminal in which resistance is changed into voltage to put out, Zener diode connected between the ICs output terminal and the converter's output terminal, two resistors connected between the ICs output terminal and common terminal, and between common terminal and ground separately.
Of the above -mentioned two resistors, one is a resistor which senses any physical variable and the other is a resistor which set s up the DC stabilized voltage corresponding to the physical variable required.
The sensitive resistor is connected between the ICs common terminal and ground terminal when having the positive sensing coefficient, and is connected between the ICs output terminal and common terminal when having the negative sensing coefficient. Non-stabilized DC power supply is provided to the ICs power terminals and the load is connected to the converter's output terminals.
The load may be such displaying means as instrument or digital display, or means driven by current like relay, and the auxiliary resistor may be comprised with the load.
When the converter operates, the converted signal voltage corresponding to the physical measuring value and settled DC voltage appear as overlapped voltage in the ICs output terminal, passing through the Zener diode having the minimum Zener voltage like the settled DC stabilized voltage, the only converted signal voltage is put out to the converter's output.
Brief Description of the Drawings
FIG.1 is an example of the present invention used as the measuring device. FIG.2 is an example of the present invention controlling the physical variable.
FIG.3 is a characteristic curve of Zener diode in FIGS.l and 2. (to help the comprehension of FIGS.l and 2)
FIG.4 is a graph showing the operation of the converter having the positive sensing coefficient in FIGS.1 and 2.
Detailed Description of the Drawings
The converter shown in FIGS.l and 2 consists of a IC (1), which have the input terminal l a provided by non-stabilized power through the converter's power terminal 5 a , the common terminal l c receiving resistance change and the output terminal I b in which the signal U e of the sensing resistor R 3 is changed into voltage U b to put out, Zener diode (2) connected between the ICs output terminal I b and the converter's output terminal 5 b , two resistors R 1, R 2 connected between the ICs output terminal I b and common terminal l c and between the ICs common terminal l c and ground terminal 5 C separately.
Of the above -mentioned two resistors, one resistor R 2 (or R 1 ) is a one which senses any physical variable and the other resistor Rl ( or R2) is a one
which set s up the DC stabilized voltage U b(0) ( or U bp ) corresponding to physical variable required
The sensitive resistor R s is connected to position of R 2 when having the positive sensing coefficient and to position of R 1 when having the negative sensing coefficient.
The load (4) is connected to the output terminals 5 b and 5c of the converter (5).
The device shown in FIG.l is an example of the circuits of measuring such the physical variables as temperature, light and power. If the resistive sensor R 8 have the positive sensing coefficient, it is connected in the position of R 2 and the load (4) is the instrument (41).
When the power is put on, the output voltage U b of the IC (1) is given by the following formula.
U b =U R (RR 8 ZR 1 Hl R R 2 (1) Where
U R -the reference voltage in inside of the IC ∑ R -the reference current flowing through the IC U R and I R are very small. In formula (1), as U R (RR S ZR 1 ) » I R R 2 U b OJ R (RR 5 ZR 1 ) (2)
Where the voltage U b is a one converted to be nearly proportional to the dimension of sensitive resistance.
As shown in FIG.4, supposing the voltage U b( o ) of the output terminal I b of the IC and the increased signal voltage U 8 , the voltage U b appeared to the output terminal I b of the IC (1) is as follows;
U b =U b( o ) +U s (3)
If the setting resistor R 1 is adjusted so that the original value U b(O) is equal to the minimum Zener voltage Uz Dm j n of Zener diode shown in FIG.3, the voltage U out of the output terminal 5 b of the converter(5) is as follows;
u out =u b -u ZDmin =u b -u b( orU s (4)
Therefore, the only converted signal U s appears to the output terminals 5 b and 5 0 of the converter.
This signal voltage U s is provided to the instrument (41), as a result, the physical variable is measured.
In case the voltage R 1 have the negative sensing coefficient, the operating principle of the circuit is similar to the above explanation and only the original value U b(0) of the measuring section is adjusted by the resistor R 2 that it is equal to the minimum Zener voltage Uz Dmm of Zener diode. In fact, it is carried out by the adjustment of the setting resistors R 1 or
R 2 that the instrument (41) shows the minimum value in the original value of the measuring section.
The auxiliary resistor R 3 is one which adjusts the load current IL SO that it limits the maximum current Iz Dmax flowing through the Zener diode or it shows the maximum value of the instrument (41) in the maximum output voltage U smax of measuring section required, and it may be added or not added according to the conditions.
The controlling circuit of any physical variable shown in FIG.2 is equal to the distribution of the above -mentioned circuit and only the relay (42) is connected instead of the load (4).
The operating principle of the circuit is equal to the explanation of FIG.l and the only the setting method of the controlling value differs.
The controlling value is set up by the adjustment of the setting resistor R 2 (or R 1 ) that it provides the minimum operating current Iz Dm i n of the relay in the physical value aimed.
The relay (42) drives the connector or the electronic valve that it puts on or puts off, increases or decreases the controlling quantities in the current Iz Dp corresponding to the sensitive resistance R sp of physical value aimed.
The converter can be integrated into one chip and the Zener diode may be used or not be used according to the conditions.
Finally, though the general examples are given in FIGS, it is indicated that the more practical circuits will be raised. The advantages of the present invention include the ability to make the converter using the simple methods by which only one resistor of two resistances for setting the output voltage is changed to sensitive resistor and the Zener diode is connected to its output terminal ,while the IC which is only provided for the stabilizing of voltage is used as it is. For example, if this converter is introduced to the temperature measurement, the accuracy is 0.01-0.05 ° C , the output power is higher than 200-300 mV/ ° C . Thus, the measurement and control can be carried out by the only converter.
In summary, the benefits of the invention can be listed as follows:
■ All the sensors which change any physical variable into resistance can be used to the converter.
• As the converter's output have the properties of the voltage source or current source, in the permitted limits of the elements, the load of any dimension can be connected and especially it can make the devices driven by the electric current operate directly. • The required measuring section can be narrowed or extended by the selecting of the setting resistor and auxiliary resistor in the permissible measuring section.
■ The stabilized DC power supply for the operating of the converter and the converting operation of signal are to be carried out by the IC simultaneously.
• The output value of high sensitivity and accuracy, great output power can be gained directly.
• The circuit being simple, the manufacturing is easy and the costs can be saved. The manufacturing costs are lower l/5th than the former.
• The noises can be eliminated and the characteristic changes of the elements by circumstances can be decreased by the direct driving without using of the amplifying stage.