METHOD, APPARATUS AND SYSTEM FOR MONITORING SENSOR HEALTH AND GAS RESPONSE FOR CATALYTIC PELLISTOR POISONING

Methods, apparatuses, and systems for detecting catalytic pellistor poisoning of a gas sensing apparatus including a resistor, a detector, and a compensator are provided. The method includes sampling a voltage reading of the resistor, calculating an electric current value of a gas sensing apparatus circuit based on the sampled voltage reading of the resistor, sampling voltage readings associated with the detector and the compensator for a duration of time, calculating resistance values of the detector and resistance values of the compensator based on the sampled voltage readings from the detector and the compensator, comparing the resistance values of the detector with the resistance values of the compensator, and identifying poisoning of the gas sensing apparatus based on the comparison.

FIELD OF THE INVENTION

The present disclosure relates generally to monitoring functionality of gas detectors, and more particularly, to methods, apparatuses, and systems for detecting inoperability of gas detectors having catalytic pellistors.

BACKGROUND

Catalytic pellistor devices are used to detect combustible gases and vapors in the air (for example, in concentrations approaching an explosive range). While catalytic pellistor devices provide fast and accurate gas measurements by exploiting the effects of catalytic reactions, many catalytic pellistor devices are plagued by technical challenges and difficulties.

BRIEF SUMMARY

Various embodiments described herein relate to methods, apparatuses, and systems for monitoring gas detectors. In particular, various embodiments are related to detecting inoperability of a gas sensing device including a detector and a compensator.

In accordance with various examples of the present disclosure, a method is provided for detecting catalytic pellistor poisoning associated with a gas sensing device, wherein the gas sensing device comprises a circuit including a resistor, a compensator, and a detector. The method comprising determining an initial resistor voltage value of the resistor, determining an initial compensator voltage value of the compensator and an initial detector voltage value of the detector, and calculating an initial circuitry current value based at least in part on the initial resistor voltage value and a resistance value of the resistor. Subsequent to causing an injection of a gaseous substance to the gas sensing device, a subsequent compensator voltage value of the compensator and a subsequent detector voltage value of the detector are determined. A subsequent circuitry current value is calculated based on the subsequent resistor voltage value and the resistor resistance value. A compensator resistance change value is calculated based at least in part on the initial circuitry current value, the initial compensator voltage value, the subsequent circuitry current value, and the subsequent compensator voltage value. A detector resistance change value is calculated based at least in part on the initial circuitry current value, the initial detector voltage value, the subsequent circuitry current value, and the subsequent detector voltage value. The method further comprises generating a catalytic pellistor poisoning indicator based at least in part on the compensator resistance change value and the detector resistance change value.

In some embodiments, the initial detector voltage value and the initial compensator voltage value may comprise a baseline reference for establishing functionality of the detector and the compensator. In some embodiments, the baseline reference may be associated with an absence of a gaseous substance. In some embodiments, the initial circuitry current value may comprise an amount of electrical current supplied to the circuit from a supply power source before the injection of the gaseous substance. In some embodiments, calculating the initial circuitry current value may further comprise dividing the initial resistor voltage value by the resistance value of the resistor.

The method may further comprise recording a time of the injection of the gaseous substance and monitoring for changes in the subsequent compensator voltage value and the subsequent detector voltage value. In some embodiments, the subsequent compensator voltage value and the subsequent detector voltage value may correspond to a time after the injection of the gaseous substance. In another embodiment, the method may further comprise executing component failure analysis using the compensator resistance change value and the detector resistance change value.

In some embodiments, generating the catalytic pellistor poisoning indicator may comprise determining that the detector resistance change is analogous to the compensator resistance change subsequent to injection of the gaseous substance. In yet another embodiment, generating the catalytic pellistor poisoning indicator may further comprise determining decreasing detector resistance in conjunction with decreasing compensator resistance subsequent to injection of the gaseous substance. In some embodiments, the detector may comprise a catalytic pellistor including a bead structure with catalytic material. In some embodiments, the compensator may comprise a reference bead structure with non-catalytic material.

According to another embodiment, the method comprises sampling a voltage reading of the resistor and calculating an electric current value of a gas sensing apparatus circuit based on the sampled voltage reading of the resistor. In some embodiments, voltage readings are sampled from the detector and the compensator for a duration of time. In some embodiments, resistance values of the detector and resistance values of the compensator are calculated based on the sampled voltage readings from the detector and the compensator. In some embodiments, the method further comprises comparing the resistance values for the detector with the resistance values for the compensator and identifying poisoning of the gas sensing apparatus based on the comparison.

The method may further comprise calculating the electric current with a resistance value associated with the resistor and the sampled voltage reading of the resistor. In some embodiments, the electric current may be calculated by dividing the sampled voltage of the resistor by the resistance value of the resistor. In some embodiments, the electric current may be provided to the detector and the compensator. In some embodiments, the detector may comprise a catalytic pellistor including a bead structure with catalytic material. In some embodiments, the compensator may comprise a reference bead structure with non-catalytic material. In one embodiment, calculating resistance values of the detector and resistance values of the compensator further comprises dividing the sampled voltage readings from the detector and the compensator by the electric current.

According to another embodiment, a system is provided for detecting catalytic pellistor poisoning of a gas sensing apparatus including a resistor, a detector, and a compensator. The system comprises a memory device having executable instructions stored therein and a processor. In response to the executable instructions, the processor is configured to sample a voltage reading of the resistor and calculate electric current of a gas sensing apparatus circuit based on the sampled voltage reading of the resistor. The processor is further configured to sample voltage readings of the detector and the compensator for a duration of time and calculate resistance values for the detector and resistance values for the compensator based on the sampled voltage readings of the detector and the compensator. The processor is further configured to compare the resistance values of the detector with the resistance values of the compensator and identify poisoning of the gas sensing apparatus based on the comparison.

The foregoing illustrative summary, as well as other exemplary objectives and/or advantages of the disclosure, and the manner in which the same are accomplished, are further explained in the following detailed description and its accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

As described above, many catalytic pellistor devices are plagued by technical challenges and difficulties. Such devices may include a pellistor comprising a small ceramic bead cast on a coil or wires. The pellistor may include a catalyst surface and function as a heater and/or a thermometer. At an appropriate temperature, the catalyst surface causes a gaseous substance (such as a gas or vapor) to be measured by the catalytic pellistor devices reacts (e.g., combusts) with oxygen from the air. Heat produced by this reaction increases the temperature of the bead and an electrical resistance of the coil or wires. The change in resistance provides a measurement of the amount of combustible gas or vapor.

Despite their usefulness, catalytic pellistors are susceptible to poisoning, which may cause loss of sensitivity or inoperability. In the present disclosure, the terms “poisoning” or “catalytic poisoning” may refer to a decrease or loss of the pellistor's sensitivity due to deposits, debris, residues, contaminant, and/or substances that accumulate and remain on the catalyst surface of the catalytic pellistor. For example, compounds containing silicon or other adsorbent materials on the catalyst surface may impair a catalytic pellistor's gas reaction, resulting in reduced performance or failure. Catalytic poisoning is a costly problem as it can decrease the accuracy of sensor readings and destroy the usefulness of expensive catalyst systems used in gas detection.

Catalytic pellistor devices may be inspected prior to use for ensuring correct operation. For example, a controlled concentration of flammable gas may be introduced across a detector of a catalytic pellistor and monitored for an expected response (e.g., ignition and/or alarm). If the detector fails the testing condition and does not provide the expected response, the catalytic pellistor may be determined to be malfunctioning. For such testing to be effective, it should be performed regularly or as part of a maintenance schedule, which can be time consuming, expensive, and cumbersome. However, poisoning of a catalytic pellistor may occur in between inspections. For example, when an inspection identifies that a catalytic pellistor device has been malfunctioning due to poisoning, the catalytic pellistor device may have already been inoperable for a period time. The delay between the time that the catalytic pellistor device is poisoned and the time that the poisoning is identified can cause safety hazards.

Thus, there is a need for a catalytic pellistor monitoring system that provides real-time detection of malfunctioning catalytic pellistor components due to poisoning.

In accordance with various examples of the present disclosure, a catalytic pellistor may include a detector comprising catalyst-load ceramic that is sensitive to combustible gases, and a compensator which is inert. When in operation, combustible gas may be burned by the detector, causing a rise in its temperature and resistance. Heat generated from the burning can measured by the detector. Meanwhile, the compensator does not burn the combustible gas and its temperature and resistance remains unchanged or reduced in the presence of combustible gases. The compensator may provide an inactive reference to compensate for environmental factors, such as temperature and pressure. For example, temperature measured by the detector may be compared with temperature of the compensator.

In accordance with various examples of the present disclosure, a compensator and/or a detector may be in various forms. In some embodiments, the compensator and/or the detector may be in the form of a bead structure. Referring now toFIG.1, an example bead structure is shown. In particular,FIG.1provides a half cross-sectional view of an exemplary bead structure according to various embodiments disclosed herein. A metal wire coil102is disposed within a cover member104.

In some embodiments, an example gas sensing apparatus may comprise two bead members. A first of the bead structures (the “detector”) may include cover member104that comprises catalytic material. The catalytic material may allow catalytic combustion or oxidation to occur. In this regard, when a voltage is supplied to the metal wire coil102, the metal wire coil102may heat the bead member. When the voltage is high enough, the high temperature of the bead structure may cause the combustible gaseous substance to react on the detector (e.g., catalytic oxidation).

A second of the bead structures (the “compensator”) may include cover member104that comprises non-catalytic material, and may resemble the detector in other respects. In other words, the compensator does not trigger catalytic combustion or oxidation, and the combustible gaseous substance may remain inert on the compensator.

Referring toFIG.2, a schematic of a gas sensing apparatus200is provided, which may be used in accordance with various embodiments of the present disclosure. Gas sensing apparatus200comprises a gas sensing apparatus circuit including a detector202comprising a catalytic pellistor (e.g., bead structure with catalytic material) and a compensator204(e.g., bead structure with non-catalytic material) that are configured based on a bridge circuit (e.g., Wheatstone bridge circuit). The gas sensing apparatus200is supplied with an electric current210via power source208.

The metal wire coil of detector202may have an electrical resistance of RD, and the metal wire coil of the compensator204may have an electrical resistance of Rc. During normal operation in a non-poisoned state of gas sensing apparatus200, when combustible gases are present, a catalytic reaction may occur at detector202, which causes a rise in both temperature and electrical resistance RDassociated with the detector202. Meanwhile, temperature and electrical resistance of Rcassociated with compensator204may remain constant or slightly lower due to a loss of heat carried away by gas via gas thermal conductivity phenomenon. The rise and change in resistance RDof the detector202may create an imbalance in the circuit. That is, a difference between electrical resistance RDand electrical resistance of Rcmay be measured across the detector202as a gas output signal206. Gas output signal206may comprise a value that is proportional to a concentration of combustible gas being detected. As such, the gas concentration can be determined based on the resistance RDof the detector202.

In the event of mild poisoning of the gas sensing apparatus200, functionality (e.g., catalytic reaction) of detector202may be reduced, causing a reduction in temperature increase and a reduction in increase of electrical resistance RD, resulting in gas output signal206to be inaccurate or inconsistent with the concentration of combustible gas (relative to normal operation). In the case of extreme poisoning, functionality of detector202may be faulty or non-existent, thereby causing no increase in temperature or electrical resistance of RDand producing an erroneous gas output signal206representative of no gas being detected. In such a case, despite the compensator204being exposed to gas, the compensator204does not react with the gas, and the state of the gas sensing apparatus200electrically corresponds to a state when there is zero gas. Thus, extremely poisoned gas sensing apparatus200cannot be used as intended (e.g., as a safety device).

According to various embodiments of the present disclosure, a gas sensing apparatus may be modified for monitoring of catalytic pellistor poisoning by adding a resistor to the gas sensing apparatus circuit and connecting measuring circuitry to metal wire coils of bead members and to the resistor. Referring toFIG.3, a schematic of a gas sensing apparatus300is provided which may be used in accordance with various embodiments of the present disclosure. Gas sensing apparatus300comprises a bridge circuit portion including a detector302comprising a catalytic pellistor (e.g., bead structure with catalytic material) and a compensator304(e.g., bead structure with non-catalytic material). For example, a first lead of the detector302is directly coupled to a first lead of the compensator304. The gas sensing apparatus300further comprises a resistor318connected in series to the compensator304(for example, a first lead of the resistor318is directly coupled to a second lead of the compensator304). A power source308is directly coupled to both the resistor318(for example, a second lead of the resistor318) and the bridge circuit portion (for example, a second lead of the detector302). As such, electric current flows from the power source308to the second lead of the resistor318and through the resistor318, from the first lead of the resistor318to the second lead of the compensator304and through the compensator304, from the first end of the compensator304to the first end of the detector302and through the detector302, and from the second end of the detector302to the power source308.

Gas sensing apparatus300further comprises measuring circuit312, measuring circuit314, and measuring circuit316. The metal wire coil of detector302may have an electrical resistance of RD, and the metal wire coil of the compensator304may have an electrical resistance of Rc. During normal operation of the gas sensing apparatus300, the values of electrical resistance of RDand electrical resistance of Rcmay have a same resistance value during a steady state (e.g., when no gas is present). However, in cases of poisoning of the gas sensing apparatus300, measuring values of RDand Rcmay be used to detect malfunctioning of at least the detector302according to various embodiments of the present disclosure. In some embodiments, resistor318may comprise a shunt resistor including a fixed value resistor. Additionally, or alternatively, resistor318may comprise a variable resistor, such as a potentiometer. Accordingly, the resistance value of resistor318may be provided, e.g., via manual input or digitally programmed/preconfigured, to programmable processor320.

Measuring circuit312is configured in parallel with resistor318. The measuring circuit312may comprise a voltage meter that comprises any combination of at least one of leads, contacts, and probes. For example, a first lead of the measuring circuit312(e.g., a voltage meter) is directly coupled to the circuit wire between the power source308and the second lead of the resistor318, and a second lead of the measuring circuit312(e.g. the voltage meter) is directly coupled to the circuit wire between the first lead of the resistor318and the second lead of the compensator304. In some embodiments, the measuring circuit (e.g. the voltage meter) is further coupled to a programmable processor320. The programmable processor320may be configured to calculate electric current310by measuring a voltage drop across resistor318using measuring circuit312and applying, e.g., Ohm's law (voltage=electric current×resistance) with the known resistance value of resistor318. The calculated electric current310is provided to detector302and compensator304in the series connection. As such, values of RDand Rcmay be calculated (e.g., Ohm's law) by programmable processor320using the calculated electric current310and voltage measurements of the detector302via measuring circuit316and of the compensator304via measuring circuit314. For example, measuring circuit314is configured in parallel with compensator304and measuring circuit316is configured in parallel with detector302. The measuring circuit314and measuring circuit316may each comprise any combination of at least one of leads, contacts, and probes coupled to a voltage meter (not illustrated) and coupled to the programmable processor320. For example, a first lead of the measuring circuit314(e.g. a voltage meter) is directly coupled to the circuit wire between the first lead of the resistor318and the second lead of the compensator304, and a second lead of the measuring circuit314(e.g. the voltage meter) is directly coupled to the circuit wire between the first lead of the compensator304and the first lead of the detector302. Similarly, a first lead of the measuring circuit316(e.g. a voltage meter) is directly coupled to the circuit wire between the first lead of the compensator304and the first lead of the detector302, and a second lead of the measuring circuit316(e.g. the voltage meter) is directly coupled to the circuit wire between the second lead of the detector302and the power source306. That is, a voltage measured across detector302and the calculated electric current310may be used by programmable processor320to calculate RD. Similarly, a voltage measured across compensator304and the calculated electric current310may be used by the programmable processor320to calculate Rc.

Resistance values of the detector302and compensator304may be monitored by programmable processor320during operation of gas sensing apparatus300. The programmable processor320may be implemented as, for example, various devices comprising one or a plurality of microprocessors with accompanying digital signal processors; one or a plurality of processors without accompanying digital signal processors; one or a plurality of coprocessors; one or a plurality of multi-core processors; one or a plurality of controllers; processing circuits; one or a plurality of computers; and various other processing elements (including integrated circuits, such as ASICs or FPGAs, or a certain combination thereof). In some embodiments, the programmable processor320may comprise one or more processors.

The programmable processor320may be configured to recognize that, during normal operation and in a non-poisoned state of gas sensing apparatus300, the resistance value RDof detector302may increase in reaction to gas (e.g., caused by a catalytic reaction). The increase in resistance value RDof detector302may be confirmed with a higher gas output306reading to confirm that a normal gas reaction is occurring. Various gas output306and resistance value RDfor a non-poisoned state may be stored to establish baseline functionality of gas sensing apparatus300. Furthermore, the programmable processor320may also be configured to account for loss of heat carried away by gas due to gas thermal conductivity phenomenon, which may cause the resistance value Rcof compensator304to decrease due to loss of heat carried away by gas due to gas thermal conductivity phenomenon. Gas thermal conductivity phenomenon may also cause the resistance value RDof detector302to decrease, particularly when detector302is poisoned and does not react to the gas. However, the decrease in the resistance value RDof detector302due to gas thermal conductivity may be offset by the increase in the resistance value RDof detector302due to heat produced by a reaction to gas by the detector302, particularly when detector302is not poisoned. As such, resistance values corresponding to the detector302and the compensator304may be used by the programmable processor320to determine if the detector302is poisoned while exposed to gas.

According to one embodiment, poisoning state of the detector302may be confirmed by the programmable processor320by checking the resistance of compensator304. For example, when the detector302is exposed to gas, the programmable processor320may detect a decrease in resistance value RDand a decrease in resistance value Rc, indicating that detector302is not catalytically reacting to the gas, and both detector302and compensator304are experiencing loss of heat by introduction of the gas. Programmable processor320may also identify reduced function of detector302when exposed to gas due to mild poisoning. That is, the programmable processor320may compare readings of gas output306, resistance value RD, and resistance value Rcwith the baseline functionality discussed above. Resistance value RDfor a given gas output reading that is lower than a baseline resistance value RDfor the same given gas output value may indicate reduced reaction of detector302to the gas, and mild poisoning of the detector302. According to another embodiment, detector functionality may be measured based on a ratio of power at the detector302(e.g., power=current×voltage) to resistance value RD.

FIG.4presents measurement readings associated with normal operation of a gas sensing apparatus according to the operations performed by a computing device in accordance with various embodiments described herewith. A computing device, for example, comprising programmable processor320, may receive or sample signals from measuring circuits312,314, and316of gas sensing apparatus300. The computing device may process the signals and generate data readings for a monitoring user interface400. Monitoring user interface400includes a circuit current channel402, a detector resistance channel404, and a compensator resistance channel406. The circuit current channel402may correspond to an electric current calculated for the gas sensing apparatus300(e.g., calculated electric current310) using techniques described herein. The detector resistance channel404and the compensator resistance channel406may correspond to calculated resistance values for detector302and compensator304, respectively, also as discussed herein. Data readings associated with channels402,404, and406are plotted along a horizontal time axis measured in seconds, and dual vertical axes including resistance measured in ohms and electrical current measured in milliamperes (mA).

According to the illustrated embodiment, the data values presented in monitoring user interface400may correspond to a baseline for comparison with poisoning conditions. For example, data readings associated with channels402,404, and406may be recorded during testing or calibration of gas sensing apparatus with gas. The recorded data may be used to create a reference or, in other embodiments, training data for machine learning, corresponding to normal operation of gas sensing apparatus300. In one embodiment, supervised learning is employed to create training data by associating data readings of channels402,404, and406to normal functionality of a gas sensing apparatus during no gas presence and during gas presence. The training data may then be used by a computing device to infer a function based on the training data to create an event classifier configured to detect normal and abnormal functionality of the gas sensing apparatus.

Gas presence instances408correspond to certain time periods where gas is injected (e.g., 50% Lower Explosive Limit (LEL)) into a system monitored by gas sensing apparatus300. When gas is injected during gas presence instances408, detector resistance channel404indicates significantly increased resistance values of the detector. Meanwhile, circuit current channel402indicates decreased current readings and compensator resistance channel406indicates lower resistance values during the gas presence instances408.

Gas sensing apparatus300is provided with a constant voltage during operation. The increased resistance of the detector, as indicated by detector resistance channel404, being larger than the decrease in resistance of the compensator, as indicated by compensator resistance channel406, causes an increase in the resistance/electrical impedance of the gas sensing apparatus circuit of the gas sensing apparatus300. As a result of the increased resistance/electrical impedance, the electric current310, as indicated by circuit current channel402, is reduced.

FIG.5presents measurement readings when a gas sensing apparatus is poisoned according to the operations performed by a computing device in accordance with various embodiments described herewith. According to the illustrated embodiment, the data values presented in monitoring user interface500may correspond to detection of a same or similar concentration of gas, as discussed with respect toFIG.4, but in a scenario where the gas sensing apparatus300has been poisoned by a contaminant, e.g., silicon. A computing device, for example, comprising programmable processor320, may generate data readings for the monitoring user interface500based on signals received or sampled from measuring circuits312,314, and316of gas sensing apparatus300.

Monitoring user interface500includes a circuit current channel502, a detector resistance channel504, and a compensator resistance channel506. The circuit current channel502may correspond to an electric current calculated for the gas sensing apparatus300(e.g., calculated electric current310), as discussed herein. The detector resistance channel504and the compensator resistance channel506may correspond to calculated resistance values for detector302and compensator304, respectively, also as discussed herein. Data readings associated with channels502,504, and506are plotted along a horizontal time axis measured in seconds, and dual vertical axes including resistance measured in ohms and electrical current measured in milliamperes (mA).

In the case of poisoning, detector resistance channel504indicates resistance values that are lower than the baseline, especially when gas in injected during gas presence instances508. Particularly, detector resistance channel504indicates no detection or catalytic reaction to gas during gas presence instances508. Instead, both detector resistance channel504and compensator resistance channel506indicate decreases in resistance, e.g., due to loss of heat from gas thermal conductivity. The decreases in resistance of both detector302and compensator304may cause the resistance/electrical impedance of the gas sensing apparatus circuit of the gas sensing apparatus300to decrease (and the electric current310to increase in an example where a constant voltage is applied to the circuit) when gas in injected during gas presence instances508, as indicated by circuit current channel502. Accordingly, an increase in circuit current channel502reading in combination with decreases in detector resistance channel504and compensator resistance channel506may be indicative of poisoning of detector302.

Additionally, or alternatively, by monitoring the compensator resistance channel506in relationship to the circuit current channel502, or compensator resistance per wattage of power (e.g., power=electric current×voltage), poisoning and reduced functionality of detector302may be detected and a gas alarm can be issued regardless of the value of detector resistance channel504. Resistance value per power ratio may be used as a metric for determining detector functionality based on a circuit imbalance (e.g., of the bridge circuit) as a result of lower-than-normal resistance of detector302. For example, a decrease in gas output detection due to partial poisoning, can be detected by a computing device by calculating a real-time resistance value per power ratio of the compensator304and comparing it with a baseline/historical resistance value per power ratio of the compensator304. A real-time resistance value per power ratio of the compensator304that is lower than the baseline/historical resistance value per power ratio of the compensator304may indicate partial positioning.

Referring now toFIG.6andFIG.7, example flow diagrams illustrating exemplary methods of detecting catalytic pellistor poisoning in accordance with some example embodiments of the present disclosure are provided. It is noted that each block of a flowchart, and combinations of blocks in the flowchart, may be implemented by various means such as hardware, firmware, circuitry and/or other devices associated with execution of software including one or more computer program instructions. For example, one or more of the steps/operations described inFIG.6andFIG.7may be embodied by computer program instructions, which may be stored by a non-transitory memory of an apparatus employing an embodiment of the present disclosure and executed by a processor component in an apparatus (such as, but not limited to, a gas sensing apparatus, a programmable processor, a client computing device, a remote computing server, and/or the like). For example, these computer program instructions may direct the processor component to function in a particular manner, such that the instructions stored in the computer-readable storage memory produce an article of manufacture, the execution of which implements the function specified in the flowchart block(s).

InFIG.6, the example method600may be executed by a computing device associated with a gas sensing apparatus including a detector, a compensator, and a resistor (for example, as illustrated and described above in connection with at leastFIG.3). At step602, voltage reading of a resistor is sampled from a first measuring circuit. The first measuring circuit may comprise any one of leads, probes, and contacts configured in parallel with the resistor for measuring voltage by a voltage meter coupled to the computing device.

In some embodiments, subsequent to step602, the example method proceeds to step604, where electric current of the gas sensing apparatus circuit of the gas sensing apparatus is calculated based on the sampled voltage reading of the resistor. The computing device may be configured to calculate the electric current by applying, for example, Ohm's law with a resistance value of the resistor and the sampled voltage of the resistor. The resistance value of the resistor may be a known or preconfigured resistance value that can be set as a programmable variable on the computing device. The electric current may be calculated by the computing device by dividing the sampled voltage of the resistor by the resistance value of the resistor. The calculated electric current may be representative of electric current provided to both the detector and the compensator.

In some embodiments, subsequent to step604, the example method proceeds to step606, where voltage readings associated with a detector and from a compensator are sampled for a duration of time. Sampling voltage readings associated with the detector may comprise receiving signal readings from a second measuring circuit coupled to the detector. Sampling voltage readings associate with the compensator may comprise receiving signal readings from a third measuring circuit coupled to the compensator. The second and third measuring circuits may comprise any one of leads, probes, and contacts configured in parallel with the detector and the compensator, respectively, for measuring voltages by voltage meters in communication with the computing device. The detector may comprise a catalytic pellistor including a bead structure with catalytic material. The compensator may comprise a reference bead structure with non-catalytic material, and the compensator is used in conjunction with the detector. The sampled voltage readings of the detector and the compensator may be used to calculate resistance values for the detector and the compensator, respectively.

In some embodiments, subsequent to step606, the example method proceeds to step608, where resistance values of the detector and the compensator are calculated based on the sampled voltage readings from the detector and the compensator. The computing device may calculate resistance values for the detector and resistance values for the compensator by, for example, dividing the respective sampled voltage readings of the detector and the compensator by the calculated electric current.

In some embodiments, subsequent to step608, the example method proceeds to step610, where resistance values of the detector are compared with resistance values of the compensator. The resistance values of the detector and the compensator may be indicative of their functionality. That is, the resistance values between the detector and the compensator may be compared to provide an indication of detector poisoning and overall functionality of the gas sensing apparatus. As described above, the resistance value of the detector and the resistance value of the compensator are the same when the gas sensing apparatus is not in use (e.g., when the gas is not injected to the gas sensing apparatus). When the gas sensing apparatus operates under normal condition (e.g., when there is no poisoning), resistance values of the detector may increase in the presence of a gas due to a catalytic reaction of the detector with the gas, while resistance values for the compensator decrease due to loss of heat from gas thermal conductivity. However, when the detector is poisoned, catalytic reaction to gas may be reduced, which reduces the amount of increase (or causes no increase, or a decrease due to loss of heat from gas thermal conductivity) in the resistance values of the detector, while resistance values for the compensator decrease due to loss of heat from gas thermal conductivity. In the case of extreme poisoning of the detector, catalytic reaction to gas may be non-existent and the resistance value of the detector may instead mirror a decrease in the resistance value of the compensator where both detector and compensator experience loss of heat as a result of gas thermal conductivity. As such, at step610, the example method determines whether the resistance value of the detector and the resistance value of the compensator are the same. If they are the same, the detector is poisoned.

In some embodiments, subsequent to step610, the example method proceeds to step612, where poisoning of the gas sensing apparatus is identified based on the comparison of detector resistance values with the compensator resistance values. Identifying poisoning of the detector may include determining that the detector generates no detection or catalytic reaction to gas while resistance values of the detector and resistance values of the compensator both indicate decreases, e.g., both detector and compensator are experiencing loss of heat from gas thermal conductivity. Additionally, an increase in electric current of the gas sensing apparatus may further indicate that both resistance values of the detector and the compensator are decreasing (e.g., due to imbalance of a bridge circuit of the gas sensing apparatus).

Poisoning of the gas sensing apparatus may also be identified by monitoring the resistance values of the compensator in relationship to the electric current of the gas sensing apparatus, or compensator resistance per wattage of power. Resistance value per power ratio may be used as a metric for determining detector functionality based on a circuit imbalance (e.g., of the bridge circuit) as a result of lower than normal resistance of detector. For example, a decrease in gas output detection due to partial poisoning can be detected by calculating a real-time resistance value per power ratio of the compensator and comparing it with a baseline/historical resistance value per power ratio of the compensator. A real-time resistance value per power ratio of the compensator that is lower than the baseline/historical resistance value per power ratio of the compensator may indicate partial positioning. In some embodiments, subsequent to step612, the example method may return to step602and repeat the steps of example method600for a duration of time.

Referring toFIG.7, the example method700may be executed by a computing device to test a gas sensing apparatus including a detector, a compensator, and a resistor (for example, as illustrated and described above in connection with at leastFIG.3). The detector may comprise a catalytic pellistor including a bead structure with catalytic material. The compensator may comprise a reference bead structure with non-catalytic material, and the resistance value of the compensator is matched with the resistance value of the detector.

At step702, an initial resistor voltage value of a resistor is determined. The resistor may be configured on a gas sensing apparatus circuit of gas sensing apparatus for measuring electrical current of the circuit, similar to those described above. The initial resistor voltage value may be determined by receiving voltage measurement data from a measuring circuit configured to measure a voltage drop across the resistor.

In some embodiments, subsequent to step702, the example method proceeds to step704, where an initial detector voltage value of a detector and an initial compensator voltage value of a compensator are determined. The initial detector voltage value and the initial compensator voltage value may be determined by receiving voltage measurement data via measuring circuits coupled to the detector and the compensator, respectively. The initial detector voltage value and the initial compensator voltage value may be recorded and used as a baseline reference for establishing functionality of the detector and the compensator in the absence of a gaseous substance.

In some embodiments, subsequent to step704, the example method proceeds to step706, where an initial circuitry current value is calculated based at least in part on the initial resistor voltage value and a resistance value of the resistor. The resistor voltage value of the resistor may be used to determine the initial circuitry current value. The initial circuitry current value may comprise an amount of electrical current supplied to the gas sensing apparatus from a supply power source. The resistance value of the resistor may be a known or specific value such that the initial circuitry current value may be calculated based on the initial resistor voltage value and the resistance value of the resistor. For example, the initial resistor voltage value may be divided by the resistance value of the resistor to calculate the initial circuitry current value. The initial circuitry current value may then be used to calculate initial resistance values for various components of the gas sensing apparatus, such as the detector and the compensator, to measure functionality of the various components, which is discussed in further detail below.

In some embodiments, subsequent to step706, the example method proceeds to step708, where the computing device causes an injection of a gaseous substance to the gas sensing apparatus. The injection may comprise a controlled introduction of the gaseous substance to an environment configured with the gas sensing apparatus (e.g., an environment where the detector and the compensator of the gas sensing apparatus are positioned in). The time of injection may be recorded by the computing device to monitor for changes in voltage values of the detector and the compensator.

In some embodiments, subsequent to step708, the example method proceeds to step710, where a subsequent voltage value of the resistor, a subsequent compensator voltage value of the compensator and a subsequent detector voltage value of the detector are determined, similar to those described herein. The subsequent resistor voltage value, subsequent compensator voltage value, and the subsequent detector voltage value may correspond to change in voltages of the resistor, detector, and compensator a time after the injection of the gaseous substance to the gas sensing apparatus.

In some embodiments, subsequent to step710, the example method proceeds to step712, where a subsequent circuitry current value is calculated based on the subsequent voltage value of the resistor and the resistor value. Similar to calculating the initial circuitry current value as discussed above, the subsequent resistor voltage value may be divided by the resistance value of the resistor to calculate the subsequent circuitry current value. The subsequent circuitry current value may then be used to calculate subsequent resistance values for various components of the gas sensing apparatus, such as the detector and the compensator.

In some embodiments, subsequent to step712, the example method proceeds to step714, where changes in detector and compensator resistance values are calculated. Changes in resistance values may be calculated based at least in part on the initial circuitry current value, the subsequent circuitry value, the initial detector voltage value, the subsequent detector voltage value, the initial compensator voltage value, and the subsequent compensator voltage value.

For example, an initial detector resistance value may be calculated by dividing the initial detector voltage by the initial circuitry current value and a subsequent detector resistance value may be calculated by diving the subsequent detector voltage by the subsequent circuitry value. A difference between the initial detector resistance and the subsequent detector resistance may provide a change in detector resistance value. Similarly, an initial compensator resistance value may be calculated by dividing the initial compensator voltage by the initial circuitry current value and a subsequent compensator resistance value may be calculated by diving the subsequent compensator voltage by the subsequent circuitry value. A difference between the initial compensator resistance and the subsequent compensator resistance may provide a change in compensator resistance value.

Resistance change values of the detector and the compensator may be used in executing component failure analysis by the computing device. For example, a decrease in resistance of both detector and compensator may coincide with increased current draw from a finite voltage source, indicating a potential malfunction of at least the detector.

In some embodiments, subsequent to step714, the example method proceeds to step716, where a catalytic pellistor poisoning indicator is generated based at least in part on the compensator resistance change and the detector resistance change. The catalytic pellistor poisoning indicator may comprise an alarm or alert on a user interface of a gas monitoring system. In one embodiment, generating the catalytic pellistor poisoning indicator may comprise determining that the detector resistance change is analogous to the compensator resistance change subsequent to injection of the gaseous substance. According to another embodiment, generating the catalytic pellistor poisoning indicator may comprise determining decreasing detector resistance in conjunction with decreasing compensator resistance subsequent to injection of the gaseous substance.