Field of the Disclosure

The present disclosure relates to the field of HVAC (Heating, Ventilation, Air Conditioning) systems, and in particular to monitoring an operating condition of a fluid flow regulator in an HVAC system.

Background to the Disclosure

HVAC systems installed in buildings or other installations are expected to achieve high standards of safety and reliability. HVAC systems also contribute to a building's fire safety and en vironment control. Monitoring and testing of the system is im portant for maintaining reliability and safety standards. Laws often require regular checks to be carried out on the system's performance .

One aspect of monitoring and testing a HVAC system concerns the functioning of electronically controlled flow regulators, e.g. valves and dampers, that regulate flow of fluids (gases and/or liquids, such as air and/or water). The efficiency and safety of the system may depend on the regulators functioning cor rectly. Fire dampers are examples of controlled regulators in tended to close off air passages in the HVAC system in the event of a fire, to avoid fire and smoke spreading. Smoke control dampers are examples of controlled regulators similarly intended to open to allow extraction of smoke and fumes through a venti lation duct. Other controllable flow regulators are also im portant to everyday ventilation, to efficiency of heating and air conditioning, and to maintaining the integrity of controlled atmosphere environments, such as clean rooms, laboratories and hospitals .

The conventional way of carrying out checks on flow regulators is by manually accessing, inspecting and testing each flow regu lator in situ, to verify that the flow regulator does function as required, closes tightly, and opens properly. However, man ual testing is slow, labour intensive and subject to human er ror. Many flow regulators are placed in locations making physi cal access difficult, further exacerbating problems. If checks are carried out relatively infrequently (for example, every 6 or 12 months), a malfunction may occur that is not detectable for a long time, potentially creating a hidden safety or environmental hazard.

EP-A-2697572 describes a promising alternative approach of auto mated functional diagnosis, including using an acoustic sensor within the flow path for monitoring whether a flow regulator is potentially leaking when in its closed condition.

It would be desirable to enhance the versatility and/or efficacy of automated monitoring of an HVAC flow regulator and/or to ad dress or mitigate remaining technical challenges.

Summary of the Disclosure

Aspects of the disclosure are identified in the claims.

Additionally or alternatively, a first aspect of the disclosure provides a method of detecting an operating condition of a con trollable flow regulator in a fluid flow channel of an HVAC sys tem. The method comprises: (a) transmitting a sonic signal, from a sonic transmitter, di rectly or indirectly to the flow regulator,

(b)receiving a signal from a sonic receiver for detecting the transmitted signal after interacting with the flow regulator; and

(c) determining, in an electronic signal processor, the operat ing condition of the flow regulator on the basis of at least the signal received in the receiving step (b).

Additionally or alternatively, a similar second aspect of the disclosure provides an HVAC flow regulator monitoring system for monitoring an operating condition of a controllable flow regu lator in a flow channel of an HVAC system, the monitoring system comprising : a sonic transmitter for transmitting a sonic signal directly or indirectly to the flow regulator, and an electronic driver for driving the transmitter; a sonic receiver for detecting the transmitted signal after in teracting with the flow regulator; and outputting a received signal; and an electronic signal processor coupled to the receiver, and re sponsive at least to the received signal, for determining the operating condition of the flow regulator

In the first and/or second aspect, the sonic signal may be dis tinguished from background noise by being at least one of: (i) modulated according to a modulation schema, (ii) an ultrasonic signal, (iii) a frequency selected to be away from background noise.

Such a technique provides considerable advantages compared to prior art. The inventors have appreciated that acoustic moni toring can be impacted negatively by an HVAC system being an unpredictably noisy acoustic environment. Background acoustic noise may be generated by the HVAC equipment itself, especially equipment in need of maintenance or replacement. Background noise may also come from the building or environment in which the HVAC system is installed. The techniques of the present in vention can enable the impact of background noise to be miti gated, and enable the sonic signal to be more easily discrimi nated in the received signal and processed to determine the op erating condition.

The modulation schema, if used, may be selected as at least one of: frequency modulation; amplitude modulation; a coded pattern of signal bursts; phase keying; phase modulation. As well as facilitating discrimination from background noise, a modulation schema also enables timing information to be derived from the received signal. Timing information may be derived from any suitable portion of the modulation schema, for example, the mark-space ratio of signal bursts, the periodicity of signal bursts or between consecutive signal bursts, the start and/or end of each signal burst, or regular clocking forming part of the modulation schema. Deriving timing information is a signif icant advantage because it can enable the transmitting and re ceiving to be performed independently, for example, by different circuitry that is not directly connected electrically. The re ceiving and/or processing can be synchronised to the transmit ting using timing information derived from the received signal. Important applications of this technique enable, for example, a time of flight to be calculated for the signal to travel from the transmitter to the receiver, and/or enable electrical sepa ration of the transmitter and receiver on opposite sides of, for example, a fire-wall, thereby avoiding any need to drill an un desirable aperture in the fire-wall for an electrical connec tion. Phase-shift keying and/or phase modulation (for example, binary phase-shift keying (BPSK)) is a technique in which the phase of a carrier signal is varied according to a message signal (the message signal being digital or analogue for phase-shift keying or phase modulation, respectively). An advantage of phase key ing and/or phase modulation is its robustness against noise.

This can be an advantage in cases of poor signal to noise ratio, such as high levels of background noise, or for providing good sensitivity to only small amplitude signals arriving at the re ceiver. The amplitude of the sonic signal may be small, for ex ample, if there is only a very small leakage path at the flow regulator that allows only a small fraction of the sonic energy to pass to the receiver. Another situation in which the ampli tude of the sonic signal may be small is when the flow channel duct has a relatively large cross-sectional area, such that the sonic energy from the transmitter is relatively diffuse over the entire area. Empirically, this can occur, for example, in a flow channel duct having a lateral dimension of at least 30cm. This is in contrast to the situation in a relatively smaller size duct, in which the sonic energy is significantly more con centrated.

The sonic signal may be modulated to carry a digitally coded signal. Digitally coding the modulated signal adds an additional characteristic of the modulated signal that can be used to as sist in discriminating the transmitted signal, even when the signal to noise ratio is very poor, for example, less than one (meaning the noise and signal have the same power) or less than zero decibel (a ratio of 1 is zero decibel).

In some embodiments, the digitally coded signal may comprise (at least part of the time) a fixed code (for example, representing invariable data). Additionally or alternatively, the digitally coded signal may, in some embodiments, comprise (at least part of the time) a variable code (for example, for transmitting var iable information). The coding scheme may comprise one or more selected from: convolutional code, trellis code, turbo code.

Additionally or alternatively, the digitally coded signal may comprise coding redundancy and/or error correction information. Such a technique can further facilitate decoding of transmitted information, even when the signal to noise ratio is very poor, for example, less than one (meaning the noise and signal have the same power) or less than zero decibel (a ratio of 1 is zero decibel) .

Additionally or alternatively to use of modulation, the ultra sonic signal, if used, can provide several advantages compared to an audible acoustic signal. One advantage is that an ultra sonic signal is not audible or perceptible to people working in the building in which the HVAC system is installed, and so peo ple will not be disturbed by hearing the transmitted signal. Another advantage is that the higher frequency of an ultrasonic signal (shorter wave period than an audible signal) enables greater time resolution (e.g. time of flight) in signal measure ments. More information can be derived in a shorter time inter val, leading, for example, to more accurate and/or more rapid determination of the operating condition. A further advantage is that ultrasonic signals are more sensitive even to the pres ence of small leakage paths at the flow regulator, than are au dible acoustic signals. In other words, even a small imperfec tion in fluid-tightness may be more easily detected using an ul trasonic signal than an audible signal. A yet further advantage is that an ultrasonic signal can enable optional calculation of fluid flow rate through the flow regulator (when the regulator is open to flow), using variation in signal time of flight between transmitter and receiver. This enables the same trans ducers to provide multiple measuring functions, without the cost and complication of a dedicated flow sensor.

In addition to the above advantages, ultrasonic signals are sub ject to greater damping resulting in more rapid attenuation with distance, compared to audible frequencies. Such attenuation is especially noticeable in air and other gaseous fluids. Back ground noise in the ultrasonic frequency range is also subject to damping and attenuation. Using ultrasonic frequencies can therefore provide a local signal environment that can be sub stantially less affected by distant sources of background noise, than using audible frequencies.

The ultrasonic signal, if used, may optionally be in a frequency range greater than 20KHz, up to 10MHz. In some embodiments, the ultrasonic frequency may optionally be at least 20.5 KHz, op tionally at least 21KHz, optionally at least 25KHz. The fre quency or frequency range may be chosen based on a number of factors, optionally including the nature of the fluid in the flow path, and/or optionally the nature of the environment in cluding background noise (discussed below). Although not limit ing, for air or other flow gases, the ultrasonic signal may be in a frequency range selected from: greater than 20KHz up to 300KHz, optionally from 25KHz to 300KHz, optionally greater than 20KHz up to lOOKHz, optionally from 25KHz to lOOKHz. Also, alt hough not limiting, for water or other flow liquids, the ultra sonic signal may be in a frequency range selected from 1MHz to 10MHz, optionally from 1MHz to 5MHz. Signals outside the exam ple ranges for different types of fluids may also be used.

In a particular embodiment, the sonic signal is (i) modulated according to a modulation schema; and (ii) an ultrasonic signal. Optionally, the signal carries digitally coded information to further improve resilience to noise, and enable operation even in poor signal-to-noise ratio conditions.

Additionally or alternatively to the above, the frequency se lected to be away from background noise, if used, may provide a further alternative even optionally using non-ultrasonic signals (e.g. signals in a frequency range of 20Hz to 20KHz) and/or non- modulated signals (e.g. continuous signals). The frequency may be selected dynamically in situ by measuring or analysing noise in respective frequency spectrums, and selecting an operating frequency away from noise. The noise analysis may optionally be repeated periodically to ensure that the operating frequency is optimal with respect to the current noise spectrum. Alterna tively, noise may be measured or analysed at installation of the HVAC system, and an appropriate frequency selected and thereaf ter fixed.

Although the options of a modulation schema, an ultrasonic sig nal, and a frequency selected to be away form background noise, may be used independently, it will be appreciated that addi tional synergistic advantages may result from combining any two or all three options together.

Additionally or alternatively to any of the above, the transmit ted signal may be transmitted directly to the flow regulator, by at least one sonic transmitter coupled to a flow control member of the flow regulator.

Additionally or alternatively, the transmitted signal may be transmitted indirectly to the flow regulator by at least one sonic transmitter transmitting the sonic signal into the flow channel on a first side of the flow regulator. Optionally, the sonic transmitter is coupled to an exterior of a conduit defin ing the flow channel, and transmits the sonic signal through the conduit wall into the flow channel. Such an exterior sonic transmitter may be a clamp-on unit, optionally facilitating mounting to an existing conduit without needing adaptation of the conduit wall.

Additionally or alternatively to any of the above, at least one sonic receiver may be coupled to the flow control member of the flow regulator. Additionally or alternatively, at least one sonic receiver may be coupled to the flow channel, optionally to an exterior of a conduit defining the flow channel and receiving the sonic signal through the conduit wall. Such an exterior sonic receiver may be a clamp-on unit, optionally facilitating mounting to an existing conduit without needing adaptation of the conduit wall.

In some embodiments, at least one sonic receiver may be posi tioned to detect the sonic signal from the flow channel on an opposite second side of the flow regulator to the transmitter. The received signal may then be processed as a component of the transmitted signal transiting the flow regulator, from one side to the other.

Additionally or alternatively, at least one sonic receiver may be positioned to detect the sonic signal from the flow channel on the same first side of the flow regulator as the transmitter. The received signal may then be processed as a component of the sonic signal reflected back by the flow regulator.

More than one sonic transmitter and/or more than one sonic re ceiver may be used per flow regulator. For example, multiple sonic transmitters and/or multiple sonic receivers may be arranged at different positions around a flow axis; and/or mul tiple sonic transmitters and/or multiple sonic receivers may be arranged on opposite sides of the same flow regulator. A first transmitter on a first side of the flow regulator may transmit a first signal in one direction to an opposite second side of the flow regulator, and a second transmitter on the second side may transmit a respective second signal in the opposite direction to a receiver on the first side. The first and second signals may be distinguished from each other (e.g. by frequency separation or time division multiplexing). Bi-directional signal transmis sion can provide a technique for avoiding any direction-depend ency in the influence on the sonic signal. Bi-directional sig nal transmission can also enhance accuracy in, for example, cal culation of fluid flow rate, if used. It is envisaged that a sonic transmitter (e.g. a single transmitter unit) may transmit the sonic signal via one or more flow paths to multiple flow regulators to provide a common sonic signal source usable to monitor operating conditions at multiple flow regulators.

As used throughout, the term "operating condition" covers one or more measurables, optionally plural measurables in parallel.

The term includes one or more of: an operating state of the flow regulator, for example, any of open, closed, fluid-tight, non fluid-tight; and/or a performance condition of the flow regula tor, for example, whether operation of the flow regulator is compromised by a performance-limiting condition or malfunction condition, such as but not limited to any of worn, broken, ob structed, in need of inspection.

In some embodiments, the operating condition is or comprises one or more of:

(i) a degree of fluid-tightness of the flow regulator when in a closed condition; (ii) the presence or absence of a leakage path through the flow regulator when in a closed condition;

(iii) a closure state and/or a closed position of the flow regu lator;

(iv) detection that the flow regulator is in a closed state;

(v) a physical position of a movable flow control member of the flow regulator, optionally a physical position of a movable vane of the flow regulator;

(vi) evolution over time of the physical position of a movable flow control member when cycled to the closed condition;

(vii) evolution over time of leak paths through the flow regula tor when cycled to the closed condition;

(vii) an indication of where around a perimeter of a flow con trol member a leakage path is detected to exist, based on a time interval between emitting of the signal into the flow channel, and reception of the signal from the flow channel;

(vi) an amount of hysteresis in the flow regulator and/or an ac tuator of the flow regulator;

(vii) distortion and/or wear of a seal component of the flow regulator, optionally, a seal member and/or a seal seat and/or a seal liner;

(viii) indication of a current and/or forthcoming malfunction of the flow regulator and/or an actuator of the flow regulator;

(ix) the degree of intactness of a flow control member of the flow regulator;

(v) indication of foreign matter in the flow channel in the vi cinity of the flow regulator, for example: accumulation of de posits; and/or contamination of the fluid; and/or pollution of the fluid.

In some embodiments, processing of the signal from the sonic re ceiver may comprise processing to determine one or more of: (i) presence or absence of the transmitted signal in a signal received from the flow channel;

(ii) an amplitude of the received signal;

(iii) a comparison of the received signal, and at least one threshold, optionally (a) a threshold for discriminating between fluid-tight and non-fluid-tight conditions, and/or (b) a thresh old for discriminating between obstructed and unobstructed flow path conditions.

(iv) a degree of attenuation of the received signal compared to the transmitted signal, as the flow regulator cycles between an open condition and a closed condition.

(v) a time interval and/or time of flight, between transmission of the signal into the flow channel, and reception of the trans mitted signal from the flow channel;

(vi) a respective phase and/or phase difference and/or phase range for a plurality of phase-distributed signal components re ceived from the flow channel;

(vii) a respective signal to noise ratio for each of a plurality of different operating frequency channels, optionally for se lecting between operating frequency channels in situ.

(viii) a measurement of noise different from the transmitted signal, optionally to facilitate selection of an operating fre quency removed from background noise.

Any possible processing technique or techniques may be used to discriminate the sonic signal in the received signal, to reject background noise, and to determine the operating condition. Merely by way of example, processing may include any one or more of: filtering, artificial intelligence, pattern recognition, data modelling, etc. The modulation schema, if used, may be se lected such that the modulation schema improves processing effi cacy for any of signal discrimination, noise rejection and de termining the operating condition. Additionally or alternatively to any of the above, a closely re lated third aspect provides an HVAC flow regulator actuator for actuating a flow regulator for regulating flow in a flow channel of an HVAC system, the actuator comprising: an electro-mechanical driver for driving movement of an actuator member, for actuating the flow regulator; and controller circuitry comprising: at least one output coupled to the electro-mechanical driver for commanding operation of the electro-mechanical driver; and at least one input for receiving an input signal from a sonic receiver for receiving a sonic signal from the flow chan nel and/or from the flow regulator; wherein the controller circuitry is operable to: identify whether the input signal comprises a component corresponding to a predetermined modulation schema and/or an ul trasonic signal component, and in response to the identification step, determine an op erating condition associated with the flow regulator and/or the actuator .

Additionally or alternatively to any of the above, a fourth as pect of the invention provides a method of operation of appa ratus for monitoring an operating characteristic of a controlla ble flow regulator in a flow channel of an HVAC system, the method comprising:

(a) during a communication cycle of operation, operating a first sonic transducer (e.g. sonic transceiver) disposed on a first side of the flow regulator to transmit a sonic signal to communicate operatively with a second sonic transducer (e.g. sonic transceiver) disposed on a second side of the flow regulator to transmit operative information from one side of the flow regulator to the other;

(b) during a measurement cycle of operation, operating the first and second sonic transducers (e.g. sonic transceivers), to detect an operating condition of the flow regulator.

The operative information may, for example, be or comprise any of: synchronisation information; command information (for exam ple, commanding the measuring cycle); result information (for example, after completion of the measuring cycle).

The method may comprise performing the communication cycle while the flow regulator is in a non-closed (e.g. at least partially or fully open condition), to provide a good and/or or unob structed path for the sonic signal to travel across the flow regulator.

The method may comprise performing the measurement cycle of op eration while the flow regulator is set to, or is being moved to a closed condition. The measurement cycle may be configured to test whether any gaps or leak paths exist when the flow regula tor is closed.

The method may optionally further comprise at least partly open ing the flow regulator at some time after the measurement cycle, to start a new communication cycle of operation.

This technique offers the possibility of using sonic signal transmission and reception in different ways. For example, when the flow regulator is known to be open (or non-closed) to pro vide a good signal transmission path, the sonic signal can be used for communication of operative information through the flow regulator and/or from one side to the other. This can avoid the need for dedicated electrical connections having to be provided crossing the flow regulator, which is especially advantageous in the case of flow regulators at fire or smoke barriers. When the flow regulator is closed, the sonic signal can be used to test or measure an operating characteristic of the flow regulator, such as whether there are any gaps or leak paths at the flow regulator. The communication cycle can optionally be used to command operation of the measurement cycle of operation, or to communicate the results of the measurement cycle.

As used throughout, the term "flow regulator" may be any device for adjusting an orifice to regulate fluid flow in a flow path, for example, a damper, a flap, or a valve. The flow regulator may be of a type having two discrete states, for example, open and closed; or the flow regulator may of a type having three or more discrete states, for example, open, closed and one or more intermediate states; or the flow regulator may be of a type that defines a continuously variable orifice size, for example con tinuously variable between fully open and fully closed. The ac- tuatable part of the flow regulator may, for example, be any movable element such as a damper blade, a valve ball, valve plug, valve flap, etc. The fluid may be a liquid (e.g. water and/or glycerol), or the fluid may be a gas (e.g. air). The flow regulator may, by way of example, be a butterfly valve or ball valve(for liquid) or a flap valve (for air). The flow reg ulator may, by way of example, be a fire-damper or a smoke- damper.

Although certain features have been highlighted above and in the appended claims, protection is claimed for any novel feature or idea described herein and/or illustrated in the drawings whether or not emphasis has been placed thereon. Brief Description of the Drawings

Fig. 1 is a schematic block diagram illustrating a first example layout of components for determining an operating condition of a flow regulator of an HVAC system.

Fig. 2 is a schematic block diagram illustrating a second exam ple layout of components for determining an operating condition of a flow regulator of an HVAC system.

Fig. 3 is a schematic block diagram illustrating a third example layout of components for determining an operating condition of a flow regulator of an HVAC system.

Fig. 4 is a schematic block diagram illustrating a fourth exam ple of component layout using multiple sonic transmitters and/or multiple sonic receivers.

Fig. 5 is a schematic block diagram illustrating a fifth example layout of components for determining an operating condition of a flow regulator of an HVAC system.

Fig. 6 is a schematic flow diagram illustrating a general method of detecting an operating condition of a controllable flow regu lator of an HVAC system.

Fig. 7 is a schematic information table illustrating example sonic signal characteristics for use in determining an operating condition of a controllable flow regulator of an HVAC system.

Figs. 8A - E are schematic graphic illustrations of sonic sig nals received by the sonic receiver, illustrating signal variation under different operating conditions of a HVAC flow regulator.

Fig. 9 is a schematic perspective view illustrating example gaps around a flow control member of a flow regulator in a nearly closed condition.

Fig. 10 is a schematic perspective view illustrating an example break in the seal around a flow control member of a flow regula tor when in the closed condition.

Fig. 11 is a schematic block diagram illustrating how time of flight information is useful for distinguishing between differ ent types of leak path at a controllable flow regulator.

Fig. 12 is a schematic graphical illustration of sonic signals received by the sonic receiver, illustrating signal variation with volume flow rate through the controllable flow regulator.

Fig. 13 is a schematic block diagram similar to Fig. 2 illus trating a flow regulator in a first operating condition, and showing use of sonic signal reflection to determine the condi tion.

Fig. 14 is a schematic block diagram similar to Fig. 13 illus trating a flow regulator in a second operating condition, and showing use of sonic signal reflection to determine the second condition.

Fig. 15 is a schematic section showing an implementation of a sonic transmitter and sonic receiver for an HVAC fire damper mounted in a fire protection wall. Fig. 16 is a schematic flow diagram illustrating method steps for selecting an operating frequency away from background noise.

Fig. 17 is a schematic block diagram of a flow regulator and as sociated actuator.

Fig. 18 is a schematic block diagram of signal processing in cluding digital coding and decoding for the sonic signal.

Fig. 19 is a schematic graph showing the use of phase-shift key ing with an ultrasonic transducer, with a 40kHz reference tone for illustration purposes.

Fig. 20 is a schematic diagram illustrating different operating cycles of a sonic transmission and reception system for communi cation and for measuring an operating characteristic of a flow regulator.

Detailed Description of Preferred Embodiments

Non-limiting embodiments of the disclosure are now described, by way of example only, with reference to the accompanying draw ings. The same reference numerals are used to denote corre sponding features, whether or not described in detail.

Referring to Figs. 1-6, the embodiments illustrate techniques for detecting an operating condition of a controllable flow reg ulator 10 in a fluid flow channel 12 of an HVAC system. The fluid may, for example, be a gas (e.g. air) or it may be a liq uid (e.g. water and/or glycol-water mixtures). Figs. 1-5 illus trate different optional layouts of certain components (dis cussed in more detail later), and Fig. 6 illustrates a methodol ogy for performing such detection of the operating condition. Referring generally to these figures, method step 14 comprises transmitting a sonic signal from at least one sonic transmitter 16, directly or indirectly to the flow regulator 10. A signifi cant feature of at least some of the techniques described herein is that the sonic signal is distinguished from background noise by being at least one of (optionally at least two, and further optionally all three of):

(i) modulated according to a modulation schema,

(ii) an ultrasonic signal,

(iii) a frequency selected to be away from background noise.

A driver circuit (not shown) may be provided to drive the sonic transmitter 16 with an appropriate signal. In some embodiments, the driver circuit is integrated as part of the sonic transmit ter 16 to form a self-contained and/or integrated unit. Alter natively, the driver circuit may form part of exterior cir cuitry, optionally part of an actuator circuit for commanding an electro-mechanical actuator for actuating the flow regulator and/or optionally part of a signal processor 24 (described be low).

Method step 18 comprises receiving a signal from at least one sonic receiver 20 for detecting the transmitted signal after in teracting with the flow regulator 10. Method step 22 comprises determining, in an electronic signal processor 24, the operating condition of the flow regulator on the basis of at least the signal received at step 18.

As illustrated later below, the above characteristics of the sonic signal enabling the sonic signal to be distinguished from background noise provide important advantages in being able to discriminate the sonic signal detected by the receiver 16, and to interpret the received signal to provide information about the operating condition.

When a modulation schema is implemented, the modulation schema may, for example, be selected as at least one of: frequency mod ulation; amplitude modulation; a coded pattern of signal bursts; phase keying; phase modulation. As well as facilitating dis crimination from background noise, a modulation schema also fa cilitates timing information to be derived from the received signal.

When an ultrasonic signal is implemented, the ultrasonic signal may optionally be in a frequency range selected from: 20KHz to 300KHz, optionally 20 KHz to 100 KHZ, for example, for air or other flow gases; or 1 MHz to 10 MHz, optionally 1MHz to 5MHz for water or other flow liquids. Use of an ultrasonic signal can avoid the signal causing audible disturbances, e.g. to peo ple in the building. Use of an ultrasonic signal can also reduce the impact of background noise from distant sources, because es pecially in air or other flow gases, background noise will in heavily damped or attenuated. As illustrated later, use of an ultrasonic signal can also provide surprisingly good sensitivity for detecting even small leak paths at the flow regulator when the regulator is closed, and/or also the ability to measure fluid flow rate when the regulator is open.

Different layouts of the sonic transmitter 16 and sonic receiver 20 with respect to the flow regulator 10 are envisaged. For ex ample, referring to Figs. 1-4, the sonic transmitter 16 may be configured to transmit the sonic signal indirectly to the flow regulator 10 via the flow channel 12. The sonic receiver 20 may be configured to detect the sonic signal via the flow channel 12. The sonic transmitter 16 and/or the sonic receiver 20 may be mounted within the flow channel as illustrated, or optionally or preferably mounted against an interior surface (not shown) of the conduit 26 defining the flow channel 12. A further possible arrangement is for the sonic transmitter 16 and/or the sonic re ceiver 20 to be mounted to an exterior surface of the conduit 26, and to transmit or receive, respectively, the sonic signal through the conduit wall. An example exterior transmitter posi tion 16' for the sonic transmitter 16 and an example exterior receiver position 20' for the sonic receiver 20 are illustrated in phantom. The sonic transmitter 16 and the sonic receiver 20 may then be configured as clamp-on units that can be clamped to or around the exterior of the conduit, without having to create a mounting aperture in the conduit wall, or pass the unit into the conduit interior space. This can greatly simplify installa tion and maintenance of the sonic transmitter 16 and the sonic receiver 20.

In Fig. 1, the sonic transmitter 16 is arranged on a first side of the flow regulator 10, and the sonic receiver 20 is arranged on a second opposite side of the flow regulator 10 for detecting a component of the sonic signal transiting the flow regulator 10. Such an arrangement is especially, but not exclusively, suitable for detecting an operating condition relating to whether the flow regulator is open or closed, and/or whether a fluid-tight seal is established, as illustrated later below.

In Fig. 2, the sonic receiver 20 is arranged on the same (e.g. first) side of the flow regulator 10 as the sonic transmitter 16, for detecting a component of the sonic signal reflected by the flow regulator. Such an arrangement is especially, but not exclusively, suitable for detecting the position (e.g. operating angle) of the flow regulator 10 and/or for detecting the degree of intactness of the flow regulator 10. Although Figs. 1 and 2 illustrate that the sonic transmitter 16 and sonic receiver 20 may be at generally matching positions with respect to the (e.g. axis of) the flow channel 12, in other embodiments, the sonic transmitter 16 and sonic receiver 20 may be in non-matching positions. In some embodiments, the sonic transmitter 16 and sonic receiver 20 may be mounted at different angular positions around the periphery of the conduit 26, such that angular positions of the sonic transmitter 16 and sonic re ceiver 20 are offset. For example, the positions may be offset by about 180°, with one being mounted near, e.g. the top of the conduit, and the other being mounted near, e.g. the bottom of the conduit. Here top and bottom are labels used to illustrate two regions offset by about 180°, but other non-aligned, and/or diagonal, arrangements of the sonic transmitter 16 and sonic transducer 20 are also envisaged.

Also, although Figs. 1 and 2 illustrate the positions of the sonic transmitter 16 and sonic receiver 20 to be generally equi distant, the distances may be different. In some embodiments, the sonic transmitter 16 may have a different angle of beam di vergence compared to the acceptance angle of the sonic receiver 20. The distance away from the flow regulator 10 may be set so as to ensure that the beam divergence of the transmitted signal can cover the entire width of the flow regulator, and/or the ac ceptance angle for the received signal can include the entire width of the flow regulator. For example, the beam divergence of the sonic transmitter 16 may be narrower than the acceptance angle of the sonic receiver 20. The sonic transmitter 16 may therefore be spaced further from the flow regulator 10 than is the sonic receiver 20. A further alternative is discussed below with respect to Fig. 4. In Fig. 3, the sonic transmitter 16 is positioned in the flow channel at a position (e.g. a central or strategic position in the HVAC system) that is remote from the flow regulator 10. The same transmitter 16 may act as a common sonic signal source for supplying the sonic signal to multiple flow regulators 10 via distributed flow channels. Each flow regulator 10 may optionally have its own sonic receiver(s) 20 for detecting the operating condition of the respective flow regulator 10. Alternatively, the same receiver 20 may act as a common sonic receiver for mul tiple flow regulators 10 coupled in a network. For example, in a series network, only one flow regulator at a time, namely the regulator to be tested, is closed, and the others are fully open. Each valve is tested in turn. The cost can thus be re duced compared to separate transducers for each flow regulator.

Additionally or alternatively, multiple sonic transmitters 16 and/or receivers 20 may be provided for a flow regulator 10, op tionally on opposite sides of the flow regulator 10. Multiple sonic receivers on opposite sides 20 may detect both transiting and reflected sonic signal components, and/or may provide a ref erence for the amplitude of the sonic signal in the flow channel 12 before interacting with the flow regulator 10.

In Fig. 4, multiple sonic transmitters 16 and/or multiple sonic receivers 20 are disposed at different respective positions around the flow axis of the flow channel 12. Such an arrange ment can provide multi-dimensional characterisation of the oper ating condition to be detected. Optionally, if multiple trans mitters are used, the transmitters may be configured to transmit at different frequencies from one another, to enable the respec tive signals to be separated and interpreted by the sonic re ceiver (s). Additionally or alternatively, the multiple trans mitters may be time division multiplexed to transmit at different times or in different transmission time windows, to avoid interference between multiple sonic signal transmissions. Additionally or alternatively, multiple transmitters and receiv ers may provide an alternative arrangement enabling devices with relatively narrow transmitted signal beam divergence and/or rel atively narrow received acceptance angle to be placed close to the flow regulator to improve signal-to-noise ratios, while col lectively ensuring that the entire width of the flow regulator is covered functionally by a combination of at least one sonic transmitter and at least one sonic receiver.

The same principles as above for separating transmissions from two sonic transmitters 16 may also be applied to the arrangement described above for Fig. 3 in which multiple transmitters 16 may be disposed at least one on each side of the flow regulator 10 in addition to a respective receiver 20 on each side. Such an arrangement provides for bidirectional transmission of a sonic signal across the flow regulator 10.

In Fig. 5, the sonic transmitter 16 is coupled to a flow control member 28 of the flow regulator 10, for directly transmitting the sonic signal to the flow regulator 10. The sonic receiver 20 is also coupled to the flow control member 28, optionally at a different position from the transmitter 16 and/or on an oppo site face of the flow control member 28 with respect to the transmitter 16. Such an arrangement is especially, but not ex clusively, suitable for detecting the operating condition on the basis of how the flow control member 28 is constrained against vibration. For example, if the flow control member 28 is tightly seated in a seal around its entire periphery, the pe ripheral edge will be constrained against vibration. Alterna tively, if the edge is not tightly seated in a seal, the edge will be less constrained against vibration, and this different response of the flow control member 28 can be detected by the sonic receiver 20.

As illustrated in selected examples below, the operating condi tion may be or may comprise one or more of:

(i) a degree of fluid-tightness of the flow regulator when in a closed condition;

(ii) the presence or absence of a leakage path through the flow regulator when in a closed condition;

(iii) a closure state and/or a closed position of the flow regu lator;

(iv) detection that the flow regulator is in a closed state;

(v) a physical position of a movable flow control member of the flow regulator, optionally a physical position of a movable vane of the flow regulator;

(vi) evolution over time of the physical position of a movable flow control member when cycled to the closed condition;

(vii) evolution over time of leak paths through the flow regula tor when cycled to the closed condition;

(vii) an indication of where around a perimeter of a flow con trol member a leakage path is detected to exist, based on a time interval between emitting of the signal into the flow channel, and reception of the signal from the flow channel;

(vi) an amount of hysteresis in the flow regulator and/or an ac tuator of the flow regulator;

(vii) distortion and/or wear of a seal component of the flow regulator, optionally, a seal member and/or a seal seat and/or a seal liner;

(viii) indication of a current and/or forthcoming malfunction of the flow regulator and/or an actuator of the flow regulator;

(ix) the degree of intactness of a flow control member of the flow regulator; (v) indication of foreign matter in the flow channel in the vi cinity of the flow regulator, for example: accumulation of de posits; and/or contamination of the fluid; and/or pollution of the fluid.

In some embodiments, the processing circuit 24 may process of the signal from the sonic receiver to determine one or more of characteristics, such as any of:

(i) presence or absence of the transmitted signal in a signal received from the flow channel;

(ii) an amplitude of the received signal;

(iii) a comparison of the received signal, and at least one threshold, optionally (a) a threshold for discriminating between fluid-tight and non-fluid-tight conditions, and/or (b) a thresh old for discriminating between obstructed and unobstructed flow path conditions.

(iv) a degree of attenuation of the received signal compared to the transmitted signal, as the flow regulator cycles between an open condition and a closed condition.

(v) a time interval and/or time of flight, between transmission of the signal into the flow channel, and reception of the trans mitted signal from the flow channel;

(vi) a respective phase and/or phase difference and/or phase range for a plurality of phase-distributed signal components re ceived from the flow channel;

(vii) a respective signal to noise ratio for each of a plurality of different operating frequency channels, optionally for se lecting between operating frequency channels in situ.

(viii) a measurement of noise different from the transmitted signal, optionally to facilitate selection of an operating fre quency removed from background noise. Some example characteristics 30-38 explained further below are tabulated in Fig. 7. One or more characteristics may be used in dependently of each other, or the operating condition may be de termined based on two more characteristics. Additionally or al ternatively, the change in one or more characteristics may be determined as the flow regulator moves from open to closed (or from closed to open). Additionally or alternatively, a histori cal evolution or trend over time of one or more characteristics may be determined.

For example, one characteristic 30 may be whether or not the sonic signal can be detected (e.g. discriminated as being pre sent) in the signal from the sonic receiver 20.

Another characteristic 32 may be the amplitude of the sonic sig nal in the received signal. Amplitude can be an important char acteristic for evaluating how much of the sonic signal is trans iting or is reflecting from the flow regulator, indicative for example, of the size of the gap or orifice at the flow regula tor. Amplitude (e.g. amplitude trend over time) can also pro vide an indication of transmitter and/or receiver performance compared to expected performance over the life of the transduc ers. For example, deviation in performance may indicate actual or forthcoming malfunction. Amplitude (e.g. amplitude trend over time, for example, measured consistently at a certain pre determined opening angle) may provide an indication of a mechan ical problem, and/or the degree of pollution and/or accumulation of debris in the flow channel. Pollution or debris tends to re duce the sonic signal amplitude.

Another characteristic 34 may be the time of flight (TOF) for the sonic signal to travel from the sonic transmitter 16 to the sonic receiver 20 (or for the sonic signal to travel from one side of the flow regulator to the other, for example, in the ar rangement of Fig. 3). Time of flight can be an important char acteristic for evaluating the travel path (e.g. the length of the travel path) of the sonic signal as it transits or is re flected by the flow regulator. Time of flight can be evaluated to determine where around the periphery a leak path may exist, as well as evaluating the operating position of a flow control member of the flow regulator. Time of flight can also be evalu ated to measure the fluid flow rate when the flow regulator is open.

Another characteristic 36 may be the envelope shape of the re ceived signal compared to the transmitted signal. Envelope shape can provide useful information about the number of differ ent signal paths, and relative path lengths, along which the sonic signal may transit the flow regulator or may reflect from the flow regulator. In general, there may be multiple signal paths from the transmitter 16 to the receiver 20, including re flections from internal surfaces of the conduit 26 and the flow regulator 10. Some of the signal paths may have different lengths, creating relative phase lag between the signal paths. Superposition of signals arriving at the receiver 20 along these different paths can lead to an amplitude variation at the re ceiver. The envelope shape of this amplitude variation is a use ful indicator, independently or in combination with other char acteristics. For example, relative orientation or position of the flow control member of the flow regulator may thereby be de termined, and/or the size of the opening at the flow regulator may be indicated. The smaller the size of any gaps, the fewer sonic signal paths that will coincide at the receiver.

If envelope shape is not needed, and/or in order to determine or measure amplitude independent of envelope shape, the amplitude signal may be mathematically integrated over a time interval. Integration can cancel out temporal fluctuations, to provide an amplitude determination relatively independent of reflections and different signal paths.

Another characteristic 38 may be synchronisation or timing de rived from the received signal. Such synchronisation or timing information may be especially significant when there is no di rect electrical connection between the sonic transmitter and the sonic receiver. Synchronisation/timing information may never theless be derived independently on the receiver side (or by the processing circuitry 24) based, for example, on the modulation schema, if used.

Figs. 8-10 illustrate an example of detecting one or more oper ating conditions related to the degree of fluid-tightness of the flow regulator, based on a sonic signal transiting the flow reg ulator 10 in the layout example of Fig. 1. The graphs of Figs. 8A-E illustrate a received signal, over a short time duration, starting at "zero-time" when the sonic signal is transmitted into the flow channel. In this example, the sonic signal is an ultrasonic signal at a frequency of 40KHz. The transmitted sonic signal is non-modulated (e.g. a continuous signal of con stant amplitude).

Referring to Fig. 8A, trace 40 represents the signal received by the sonic receiver when the flow regulator is open (a flap posi tion or orientation of 0° measured with respect to a plane par allel to the pivot axis of the flap, and parallel to the flow channel axis). The time of flight T-0°, or time delay from transmitter to receiver, is indicated at 42. The received sig nal has a large amplitude, because the flow regulator is at maximum aperture or maximum orifice, enabling most of the energy of the transmitted sonic signal to transit to the sonic re ceiver.

Referring to Fig. 8B, trace 44 represents the signal received by the sonic receiver when the flow regulator is pivoted through 88°, ie. pivoted towards its closed position (at 90°), but with some gap remaining around at least a majority of the flap. It can be seen that the amplitude remains relatively strong. The time of flight T-88°, represented at 46, is noticeably longer than the fully-open position, because the gap remains only to wards the periphery of the flow channel. The sonic signal has to travel along a longer path length than in the fully-open po sition when the path-length is shortest and the path most di rect.

Referring to Fig. 8C, trace 48 represents the signal received by the sonic receiver when the flow regulator is pivoted at 89°, namely, slightly closer to the fully closed position of 90°. Referring to Fig. 9, at the 89° position, fewer and smaller gaps 50 remain around the periphery of the flow regulator, and these gaps 50 are at the extremity of the flow channel. The amplitude of the received signal is reduced because the smaller gaps re sult in less sonic energy transiting the flow regulator. Also, the time of flight T-89° represented at 52 is again noticeably longer, because the gaps are now at the extreme edge of the flow channel.

Referring to Fig. 8D, trace 54 represents the signal received by the sonic receiver when the flow regulator is pivoted fully closed at 90°, but with a break 56 in the seal creating a small leak path (Fig. 10). Even though the leak path is small, the trace 54 is still easily detectable. Use of an ultrasonic signal enables the technique to be very sensitive to any leak path. The time of flight T-90°+Leak, indicated at 58, is simi lar to T-89°, because the leak path exists at the extreme edge of the flow channel.

Referring to Fig. 8E, trace 60 represents the signal received by the sonic receiver when the flow regulator is pivoted fully closed at 90°, creating a perfect fluid-tight seal without leak age. The signal amplitude is very small, almost negligible, be cause substantially no sonic energy transits the flow regulator.

Therefore, by analysing amplitude and/or TOF information, for example, analysing how the amplitude and/or TOF change as the flow regulator cycles from open-to-closed (or closed-to-open) during a test cycle or during normal operation, the operating condition of the flow regulator can be detected and/or moni tored.

Fig. 11 illustrates a further comparison in which a small crack or other defect 70 exists in the flow control member 28 of flow regulator 10. Fig. 11 compares the path lengths between a small peripheral leak 72, and an inboard leak 74 through the small crack 70 inboard of the peripheral edge. As discussed with re spect to Figs. 8A-E, use of an ultrasonic signal makes the sys tem sensitive even to small leak paths allowing ultrasonic en ergy to transit from one side of the flow regulator to the other. A difference between a peripheral leak 72, and an in board leak 74 is that the inboard leak provides a more direct signal path than the peripheral leak. The time of flight is thus smaller for the inboard leak 74 than the peripheral leak 72. The signal amplitudes may be similar (if the leaks are of similar size), but the time of flight information enables the relative position of the leak optionally to be determined as part of the operating condition determined by the signal proces sor 24.

Fig. 12 illustrates how time of flight information is useful even when the flow regulator 10 is in its open or fully open condition, enabling the signal processor 24 to calculate fluid flow rate through the flow regulator as an operating condition without requiring the a dedicated flow rate sensor. In this ex ample, the sonic signal is an ultrasonic signal at a frequency of 40KHz, and a single signal burst is illustrated.

Trace 80 represents the signal received by the sonic receiver with the flow regulator open, but with no fluid flow. The time of flight T-0 is represented at 82. Trace 84 represents the signal for fluid flow of 100m ³ /hr. The corresponding time of flight T-100 is represented at 86. Trace 88 represents the sig nal for fluid flow of 200m ³ /hr. The corresponding time of flight T-200 is represented at 90. Trace 92 represents the signal for fluid flow of 1200m ³ /hr. The corresponding time of flight T-1200 is represented at 94. The time of flight varies with volume flow rate of the fluid. In particular, the time of flight in creases with increased volume flow rate, enabling the flow rate to be determined (either by calculation or by empirical evalua tion using known TOF information for known flow rates).

As mentioned above, both transmitters 16 and receivers 20 may be disposed on both sides of a flow regulator 10, and operated bi directionally, in such a manner that one transmitter and re ceiver pair effects detection in a first transmission direction across the flow regulator, and the other transmitter and re ceiver pair effects detection in an opposite second direction across the flow regulator. Two independent flow rate calcula tions can be performed, one being a forward direction of flow with respect to the sonic signal, and the other being a negative direction of flow with respect to the sonic signal. The two flow rate calculations can be combined to enhance an aggregate flow rate calculation.

The signal processor 24 may use the time of flight information selectively, depending on plural factors. For example, several factors may influence time of flight, including whether the flow regulator is open, closed, or partially open. As illustrated above in Figs. 8A-E, when the flow regulator moves towards its closed condition, the flow control member of the flow regulator influences the path length for the sonic signal, thereby in creasing time of flight even though volume flow decreases as the flow regulator closes. The signal processor 24 may be config ured to use time of flight selectively: (i) as part of leak-de tection when the flow regulator is nearer closed than a prede termined position threshold, or (ii) as part of volume flow rate calculation when the flow regulator is nearer open than the pre determined position threshold.

A further factor affecting time of flight information is the temperature of the fluid, because the velocity of a sonic signal in a fluid is dependent on fluid temperature. Where the temper ature of the fluid in the flow channel 12 does not vary signifi cantly in use, the temperature may be presumed to be fixed to simplify the calculation of volume flow rate. Where the temper ature may vary in use, a temperature sensor (not shown) may be provided to input additional temperature information to the sig nal processor 24. Similarly, if the flow rate is itself known (e.g. if a dedicated flow rate sensor is provided), then the time of flight information may still be useful to deduce the temperature of the fluid, even when no dedicated temperature sensor is provided. Figs. 13 and 14 illustrate a component layout similar to Fig. 2 used to evaluate the operating position and condition of a flow control member 28 of a flow regulator 10. In Fig. 13, the flow control member 28 is illustrated in its closed position gener ally perpendicular to the flow channel 12, and a distance of about 300mm from the sonic receiver 20. In Fig. 14, the flow control member 28 is illustrated in a partly open position in which the flow control member 28 is inclined, or oblique, with respect to the flow channel axis. One end 28a of the flow con trol member 28 approaches closer to the sonic receiver 30 (for example, a distance of about 280mm), while the opposite end 28a moves further away (for example, a distance of about 320mm).

The reflection of the sonic signal to the sonic receiver varies with movement of the flow control member 28, giving a different distribution of amplitude and time-of-flight characteristics. Using such characteristics, the signal processor 24 can deter mine a number of different possible conditions, such as the de tect whether the flow control member 28 is open or closed, and/or detect whether an additional part of object lies in front of the sonic receiver, and/or determine the degree of pollution in the flow channel, and/or estimate the angular position of the flow control member 28, and/or detect should a part of the flow control member break off or go missing.

Fig. 15 shows an installation example illustrating certain ad vantages of being able to separate electrically the sonic trans mitter 16 and the sonic receiver 20. Fig. 15 illustrates a flow control regulator 10 in the form of a fire damper installed in a conduit 26 traversing a fire-protection wall 100 of a building. The fire damper 10 is installed generally in register with the wall 100 such that, when the fire damper 10 is closed, it forms a barrier substantially in register with the fire protection wall 100. An electrical cable connection 102 on one side of the wall 100 (e.g. to the left in Fig. 15) provides power and con trol to the actuator 104 of the fire damper 10. The actuator is configured automatically to close the damper in the event of ab normal smoke or heat detected within the conduit 26, or in the event of loss of power via the cable 102, or in response to a control signal sent to the actuator from a system-wide control ler (not shown).

The sonic transmitter 16 and sonic receiver 20 are positioned either in the flow channel 12 or mounted externally of the con duit 26, on opposite sides of the fire damper 10, in a similar manner to Fig. 1. In the illustrated form, the sonic receiver 20 is arranged on the same side as the actuator 104, optionally to enable the signal processing circuit to benefit from being included with or as part of the actuator circuitry. However, the positions of the sonic transmitter 16 and sonic receiver 20 could be swapped if desired.

In the illustrated example, there is no electric cabling con necting directly the sonic transmitter 16 and the sonic receiver 20. Each is powered independently by electrical connections staying on the respective side of the fire protection wall 100. This avoids any need to bore any further holes through the fire protection wall 100, and thereby preserves the integrity of the wall 100 as much as possible. Even though the receiver side circuitry is independent of the transmitter side circuitry, the two sides can establish synchronisation by deriving timing in formation from a modulation schema used in the signal transmit ted by the sonic transmitter 16. For example, one such modula tion schema may comprise a repeating coded sequence of signal bursts, for example, in sequence: a first signal burst of dura tion T, a first break of duration 2T, a second signal burst of duration 2T, a second break of duration 2T, followed by a repetition starting with a next burst of duration T. The dura tion T may, for example, be about 100ms, or any other suitable unit value. Although a flow regulator 10 in the form of a fire damper is illustrated, similar principles may be used for a smoke damper.

Fig. 16 illustrates a methodology useable in some embodiments to select an operating frequency that is away from background noise. The method may be executed periodically to dynamically select and adapt the operating frequency as the background noise conditions vary. Alternatively, the method may be executed a single time during equipment installation, with the selected op erating frequency remaining fixed thereafter (optionally until subsequent maintenance).

At step 110, a sonic receiver (e.g. the sonic receiver 20 if ap propriate) is operated to receive background noise in multiple frequency channels or across a broadband spectrum. At step 112, the received signal is analysed to determine the spectrum of background noise. At step 114, selection of an operating fre quency is made such that the operating frequency is in a region of the spectrum that is free, or at least relatively free, from background noise. If multiple candidate operating frequencies are found, selection may be based, for example, on the history of candidate availability and selection, and/or on the distance of the operating frequency away from significant background noise. If the sonic transmitter 16 and sonic receiver 20 are broadband units capable of operating in any selected operating frequency (at least within a certain range), the selected oper ating frequency may be implemented by suitable control of the transmitter and/or receiver. Alternatively, the method also en visages optional step 116 at which appropriate transducers for the sonic transmitter and sonic receiver are installed. Fig. 17 illustrates functional components of an HVAC flow regu lator actuator 120 for actuating the flow regulator 10, and in terfacing with the receiver 20, and optionally with the sonic transmitter 16 (unless the sonic transmitter 16 is electrically separate from the receiver). The actuator 120 comprises an electro-mechanical driver, such as an electric motor for driving movement of an actuator member 128, for actuating the flow regu lator 10. A mechanical transmission 124 mechanically connects the motor 122 to the actuator member 128. The actuator 120 fur ther comprises electronic controller circuity 126 having an out put 130 coupled to the motor 122 for commanding operation of the motor. The controller circuitry 126 further comprises at least one input 132 for receiving a signal from a sonic receiver 20, optionally from plural sonic receivers 20. The controller cir cuitry 126 further includes the signal processor 24 as an inte gral part of the actuator 120, for detecting an operating condi tion of the flow regulator, as part of normal operation of the regulator, or as part of a dedicated self-diagnosis function 134 configured for detecting actual or forthcoming malfunction of the flow regulator 10 and/or of the actuator 120.

In some embodiments, the flow regulator 10 includes a hard-stop, including a sensor switch 136, that pre-defines the closed posi tion of the flow regulator 10 and detects when the flow regula tor reaches the pre-defined closed position. The controller circuitry 126 may include an input for such a sensor signal 138. However, since the signal processor 24 is able to detect accu rately when the flow regulator is functionally fluid-tight, without leaks, it also envisaged that a flow regulator 10 with out a hard stop, and/or without a pre-defined closed position, and/or without a physical sensor switch 136 may be used instead. The control circuitry 126 may command movement of the flow-regu lator 10 until a functionally closed condition is reached. Additionally or alternatively, the self-diagnosis model 134 of the controller circuitry may be configured to monitor the closed position, and to generate a warning indication should variation in the closed position exceed a tolerance, and/or should leakage exceed an acceptable threshold. This may, for example, be in dicative of distortion or shape set of a seal seat or seal liner used in the flow regulator 10.

Figs. 18 to 20 illustrate a further example of use of a modu lated sonic signal, which may be a modulated ultrasonic signal.

A feature of this example is that the signal is modulated to carry a digitally coded signal.

The digitally coded signal may, in some embodiments, comprise (at least part of the time) a fixed code. The fixed code may represent invariable data, for example, a code-bit or a code word. Additionally or alternatively, the coded signal may, in some embodiments, comprise (at least part of the time) a varia ble code. The variable code may be used to transmit variable information. As illustrated later below, the digitally coded signal may, in a first e.g. "communications" cycle of operation, be a variable and/or communications message for transmitting op erative information from one side of the flow regulator to an other. The digitally coded signal may, in a second e.g. "meas urement" cycle of operation, be a fixed and/or measurement sig nal for measuring an operating characteristic of the flow regu lator.

Digital coding of the modulated signal adds an extra layer of information content to the sonic signal, which can aid discrimi nation of the sonic signal at the receiver side, even when the signal-to-noise ratio is poor, for example, less than zero. The digital coding can use redundancy and/or error correction in order to enable discrimination and/or recovery of signal content that would otherwise be lost.

As well as cases of severe background noise, a poor signal-to- noise ratio may occur in many other situations. For example, in the case of a flow duct having a relatively large cross-section area, for example, a lateral dimension greater than about 250mm or about 300mm, it is challenging for a single, low-cost trans ducer to have sufficient beam width to transmit the sonic signal across the entire width or height of the duct, and/or to receive the sonic signal from the entire width and/or height. The sig nal footprint can be increased by increasing the distance be tween the flow regulator and the transducer, but attenuation of the sonic signal (especially an ultrasonic signal in air) re duces the signal strength, and reduces signal-to-noise ratio. Further, in case of a fire damper, the a major limitation is that the transducer has to be within the fire damper, which typ ically has a fixed length. A further factor when seeking to de tect small leak paths is that a small leak path only allows pas sage of a small amount of the sonic signal energy. The strength of the received signal can be extremely small, reducing the sig- nal-to-noise ratio. Efficient and reliable detection of a small leak in a flow regulator for a large duct size, using single economic ultrasonic transducers, adds technical challenges to distinguishing the sonic signal from background noise.

Figure 18 illustrates a combination of digital coding and modu lation as described above. Signal processing for the transmis sion side 200 includes a digital coding step 202 to generate a signal as a digital code. The coding step may optionally com prise including redundancy and/or error correction 204, to en hance the transmission resilience of the signal. The method fur ther includes a modulation step 206 to generate a modulated signal suitable for driving a transducer to transmit a sonic signal (e.g. an ultrasonic signal) at transmission step 208.

One example of signal modulation is phase keying (also referred to as a phase shift keying), in which the phase of a carrier signal is switched between discrete phases (e.g. two discrete phases with a 180° phase shift) to represent digital signal val ues for transmission. Fig. 19 illustrates binary phase-shift keying from an ultrasonic transducer, for example, a transducer driven at its natural frequency of 40 kHz, compared to a refer ence sinus signal 232 of the same frequency. In Fig. 19, it can be seen that the transmitted signal of the ultrasonic transducer 230 is shifting its phase by 180 degrees within relatively few pulses, for example, less than 10 pulses, of the carrier wave, thus illustrating phase keying as a viable modulation scheme for relatively low cost transducers.

Returning to Fig. 18, signal processing for the receiving side 210 includes a sonic signal receiving step 212 and demodulation step 214. The demodulated signal is passed to signal decoding step 216, which optionally applies error correction processing 218 depending on the redundancy and/or error correction used on the transmission side. Decoding and demodulation may also be linked, e.g. both steps may be iteratively repeated, or may be combined into one.

The output from the decoding step 216 may be either the decoded signal itself, and/or a signal indicative of whether a signal has been successfully received and decoded. For example, in the case of leak detection, the presence of a successfully received and decoded signal may be indicative of a leak at the flow regu lator. Fig. 20 illustrates a technique that may be used, for example, in the embodiment of Fig. 15, in which the transducers on oppo site sides of the flow regulator are electrically separated from each other. By employing the digital coding/decoding of Fig.

18, the transducers can be used to communicate operative infor mation from one side of the flow regulator to the other. Refer ring to Fig. 20, the technique may include a communication cycle (or phase) of operation 220, and a measurement cycle (or phase) of operation 222. The communication cycle 220 may be used when the flow regulator is open (e.g. has been set to open). The measurement cycle 222 may be used when the flow regulator is closed (e.g. has been set to closed), for example, for testing the integrity of the seal of the flow regulator in its closed state. The transducers may be sonic transceivers, including both transmission and reception capability, for bidirectional operation.

In one example, the communication cycle 220 is used for one transducer (for example, on the actuator side of the flow regu lator) to command the other transducer to start a measurement cycle of operation. During the measurement cycle, the commanded transducer may emit a signal for testing the seal integrity of the flow regulator. The first transducer may operate in a re ception mode for receiving the transmitted signal, to determine whether a leak path exists. The second transducer may be con figured autonomously to transmit the signal for a predetermined period of time, for example, at least or about 10 seconds, op tionally at least or about 20 seconds, optionally at least or about 30 seconds, optionally at least or about 40 seconds, op tionally at least or about 50 seconds, or optionally at least or about at least 60 seconds. The predetermined period of time may be sufficient to allow the flow regulator to close under normal circumstances, and/or provide a reliable measurement duration. The second transducer may be configured to autonomously stop transmission of the signal after the predetermined period of time. It is also envisaged that the functionality of the transducers may be reversed, such that the first transducer emits a sonic signal during the measurement cycle, and the second transducer operates in a reception mode to detect whether the sonic signal passes through the flow regulator. It will be appreciated that the foregoing description is merely illustrative of preferred embodiments of the invention, and that many modifications and equivalents may be used within the scope and/or principles of the disclosure.