JP2002055071A - Method for diagnosing gas-detection performance, and gas-detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for diagnosing gas-detecting performance and a gas detecting device capable of performing detailed evaluation on the degree of deterioration of a semiconductor-type gas detecting element. SOLUTION: The reference output stabilization time measured at reenergization, when the switching between energization and non-energization of the undegraded semiconductor-type gas detecting element 10 is repeated a plurality of times is compared with the measurement output stabilization time measured at re-energizatiom when the switching between energization and non-energization of a semiconductor-type gas detecting element 10, which is an object of diagnosis, a plurality of times. When a ratio between the reference output stabilization time and the measurement output stabilization time exceeds a prescribed value, it is diagnosed that the semiconductor- type gas detecting element 10, the object of diagnosis, is degraded in the method for diagnosing gas detection performance. The method for diagnosing gas detection performance is provided with the semiconductor-type gas-detecting element 10, a gas- detecting circuit 20 capable of measuring the resistance value of the semiconductor-type gas-detecting element 10, and an output measuring mechanism 40 for measuring the output stabilization time at re-energization, when energization is repeated a plurality of times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing gas detection performance of a semiconductor gas detection element containing a metal oxide semiconductor as a main component and a metal oxide semiconductor provided so as to be freely contacted with a gas to be detected. The present invention relates to a gas detection device provided with a gas detection circuit capable of measuring a resistance value of a semiconductor gas detection element by applying a gas detection voltage to the semiconductor gas detection element as a component.

[0002]

2. Description of the Related Art A semiconductor type gas detecting element has a gas sensitive portion mainly composed of a metal oxide semiconductor, and is provided so as to be freely contacted with a gas to be detected (hereinafter referred to as a gas to be detected). The gas to be detected contacts the semiconductor type gas detection element,
The gas sensitive portion is oxidized by the metal oxide semiconductor, and the resistance value of the semiconductor gas detecting element changes quantitatively with the transfer of electrons accompanying the oxidation reaction. Therefore, the gas detection device including the semiconductor-type gas detection element can obtain the concentration of the gas to be detected from the output value based on the change in the resistance value.

[0003] In such a semiconductor type gas detecting element, the reactivity with the gas to be detected in the sensitive portion gradually changes in response to the reaction with the gas to be detected in the process of being used, so that a sufficient amount of the gas is detected. It is known that degradation occurs in which reactivity cannot be obtained. Such deterioration is spontaneous deterioration. In addition, deterioration caused by poisoning the semiconductor-type gas detection element due to the presence of a poisoning gas is known.

Further, when such a change in the reactivity of the sensitive part occurs, the semiconductor type gas detection element has an abnormally large or small gas detection output as compared with a normal output. Or may be. In such a case, based on the stable output for the gas to be detected that does not contain the gas to be detected, it is determined how much output the semiconductor-type gas detection element shows for the gas to be detected at a predetermined concentration. From the output ratio between the output and the output when the semiconductor gas detection element is not deteriorated, the detection output of the semiconductor gas detection element with respect to the detection gas is calibrated to detect the detection gas. ing. Such adjustment is called zero span adjustment. At this time, if the output ratio exceeds the calibrable capacity of the gas detection device (for example, the capacity of an amplifier provided in the gas detection device), the semiconductor gas detection element deteriorates and the gas detection is performed. Diagnosis of reduced performance has been made.

[0005] Further, in the gas detecting device provided with such a semiconductor type gas detecting element, when the stable output is obtained, the gas detecting device is used as it is for detecting the gas to be detected. The output stabilization time until the output is obtained does not matter.

[0006]

However, when diagnosing the gas detection performance of the semiconductor gas detection element as described above, when it is diagnosed that the semiconductor gas detection element is deteriorated, the diagnosis is already performed. Semiconductor type gas sensing elements have been treated as unusable. In addition, the actual user often notices the abnormality of the semiconductor type gas detection element after such a state that it clearly cannot withstand use.

In particular, when it is desired to detect a gas to be detected with a high degree of accuracy, if the characteristics of the semiconductor type gas detection element have changed, even if the detection output is calibrated by the output ratio as described above, It is hard to say that the accuracy is compensated. Further, by adjusting the semiconductor gas detection element by calibrating the detection output, even when the semiconductor gas detection element can be used, normal semiconductor gas detection such as prolonged initial stabilization time and increased sensitivity to gases other than the gas to be detected. In many cases, the characteristics of the sensing element cannot be maintained.

In such a case, if it is possible to investigate in advance how much the semiconductor-type gas detecting element has, or if there is a change in the characteristic, how much the deterioration has occurred, it is necessary to respond to it. It is considered that appropriate measures can be taken, for example, by replacing the semiconductor gas detection element, adjusting the sensor sensitivity of the semiconductor gas detection element, and calibrating the obtained gas detection output value.

In addition, it is preferable that the deterioration of the semiconductor gas detecting element itself can be determined even when conditions that cannot be calibrated due to other causes are satisfied, and whether the semiconductor gas detecting element needs to be replaced during maintenance of the gas detecting apparatus. If you can judge, it is fine. Also, as for the gas detection device, it is preferable that the evaluation of the semiconductor type gas detection element can be easily performed.

In addition, the need to replace a semiconductor gas sensing element that has been deteriorated due to a change in characteristics with a semiconductor gas detection element that has not deteriorated occurs when the characteristics of the semiconductor gas detection element change significantly. In other words, the semiconductor gas sensing element in actual use shows behavior that is significantly different from the characteristics of the semiconductor gas sensing element that has not deteriorated, and the semiconductor gas sensing element that has not deteriorated even if the zero span is readjusted. When the output cannot be obtained to the same degree as the characteristic indicated by the sensing element, the necessity of replacement occurs.

However, according to the method of knowing the replacement time of the semiconductor gas detecting element by the readjustment of the zero span described above,
Since the zero span is adjusted without knowing the degree of deterioration until the time when replacement is necessary, it is not possible to judge the degree of deterioration of the semiconductor gas detection element in a state where the characteristic change of the semiconductor gas detection element is small. It was difficult. In addition, when the characteristic change of the semiconductor gas detection element occurs, it is generally determined whether the semiconductor gas detection element is caused by the gas detection circuit or a gas detection circuit other than the semiconductor gas detection element. It was difficult for the user to determine.

Accordingly, an object of the present invention is to provide a gas detection performance diagnosis method and a gas detection device capable of evaluating the degree of deterioration of a semiconductor gas detection element in more detail. .

[0013]

Means for Solving the Problems The present inventors have found that when a deteriorated semiconductor type gas sensing element is switched from a non-energized state to an energized state, the semiconductor type gas sensing element obtained based on the energization is obtained. Output, the initial stabilization time required to stabilize, along with empirically finding that it changes according to the degree of deterioration of the semiconductor gas detection element, the initial stabilization time is the initial stabilization time It has been newly found that, depending on the duration of the non-energized state, a plurality of times of energization, upon re-energization when the switching of the non-energized state is repeated, does not depend on the duration of the non-energized state. The present invention has been made.

The output stabilization time referred to in the present invention means that when a semiconductor gas sensing element is energized, a predetermined output is stably obtained in an atmosphere to which the semiconductor gas sensing element is exposed. Indicates the time until. Normally, when the semiconductor type gas sensing element is switched from the non-energized state to the energized state, the output changes with the lapse of time to an output corresponding to the concentration of the gas to be detected in the atmosphere. For example, it is known that an output corresponding to a detected gas concentration of 0 is scheduled, and an output different from the expected output is temporarily generated until the output value is stabilized. In addition, a semiconductor gas sensing element that has not deteriorated is, for example, a semiconductor gas sensing element that is not actually used after manufacturing or a semiconductor gas sensing element that is hardly used and whose output characteristics are actually used. Refers to a semiconductor gas sensing element having substantially no change compared to the previous output characteristics. The semiconductor gas sensing element to be diagnosed is usually a semiconductor gas sensing element that is actually used. In general, such a semiconductor gas detection element determines how long a non-energized state has been maintained,
It is difficult to judge in appearance.

[Structure 1] A feature of the present invention for achieving this object is a method for diagnosing gas detection performance of a semiconductor gas detection element containing a metal oxide semiconductor as a main component. The standard output stabilization time measured at the time of re-energization when the switching of energization and non-energization of the semiconductor gas detection element that has not deteriorated a plurality of times is repeated, and the semiconductor gas detection element to be diagnosed is A plurality of times of energization, comparing the measurement output stabilization time measured at the time of re-energization when switching of non-energization is repeated, if the ratio between the measured output stabilization time and the standard output stabilization time exceeds a predetermined value Another object of the present invention is to diagnose that the semiconductor gas detection element to be diagnosed is deteriorated.

[Effect 1] That is, the measurement output stabilization time is increased when re-energization is performed for the second or subsequent energization when switching between energization and non-energization of the semiconductor gas detection element to be diagnosed is repeated a plurality of times. When measured, the measured output stabilization time indicates the degree of deterioration of the semiconductor gas detection element to be diagnosed, and the higher the degree of deterioration,
Stabilization times tend to be long. Further, in this case, the output stabilization time in the case where the duration of the non-energized state is almost equal to zero is required.
The semiconductor gas detection element to be diagnosed can be objectively determined irrespective of how long the non-energized state has been maintained for how long.

Here, generally, the output stabilization time of the semiconductor gas sensing element is shorter at the second and subsequent re-energization times than at the initial energization time. This is presumably because the semiconductor gas detecting element is warmed by the initial energization, and the output of the semiconductor gas detecting element quickly reaches a temperature at which the output of the semiconductor gas detecting element stabilizes during the second or subsequent re-energization.

At the time of the above-mentioned initial energization, the same effect as that of applying a purge voltage by applying a pulse and heating by energization is obtained, and the adhered substances such as gas and moisture adsorbed on the semiconductor type gas detection element are volatilized and removed. I can do it. Then, since the output at the time of the re-energization hardly depends on the deposits, the output quickly reaches a stable output, and the stable output value hardly varies.

As described above, the standard output stabilization time measured at the time of re-energization of the semiconductor gas detection element which has not deteriorated when the energization and non-energization switching is repeated a plurality of times, and the semiconductor gas detection object to be diagnosed By comparing the measured output stabilization time measured during re-energization when the element is repeatedly switched between energized and de-energized multiple times, how long has the non-energized state been maintained? Regardless of this, it is possible to provide a method for diagnosing the performance of the gas detection element under the condition that the duration of the non-energized state is substantially equal to zero. In other words, the energization conditions at the time of diagnosis between the semiconductor gas detection element that has not deteriorated and the semiconductor gas detection element to be diagnosed are set to be equal, and the characteristics of each semiconductor gas detection element are quantified as the output stabilization time. By doing so, the degree of deterioration can be objectively determined.

Therefore, when the degree of deterioration is diagnosed on the basis of such an evaluation, if the measured output stabilization time / standard output stabilization time does not exceed a predetermined ratio, it is equivalent to a semiconductor gas detection element which has not deteriorated. It has a characteristic of and still withstands use, and has a characteristic different from that of a semiconductor gas detection element that has not deteriorated if the measured output stabilization time / standard output stabilization time exceeds a predetermined ratio. It can be regarded as an element that cannot be used for highly accurate gas detection, that is, a deteriorated semiconductor gas detection element.

That is, the result of comparison between the measured output stabilization time and the standard output stabilization time serves as a criterion for judging the necessity of replacement with a semiconductor gas detection element that has not deteriorated. Even if it is determined that there is no need, if the characteristics have changed, since it is determined that continuous use is possible due to measures such as re-adjustment of the zero span of the semiconductor gas detection element that has been diagnosed, Not only whether it has deteriorated, but also how much it has deteriorated can be shown as an objective numerical value, the replacement time is determined according to the purpose, application, etc., and the degree of deterioration is determined according to the degree of deterioration. You can now respond.

Further, since the diagnosis can be made only by using the objectively obtained ratio, it can be determined easily and quickly by ordinary users as compared with the conventional method in which the diagnosis is performed by adjusting the gas detection device. It has become possible to provide a gas detection performance diagnosis method that can perform the method.

[Structure 2] In order to achieve this object, the present invention is characterized in that the semiconductor gas sensing element is switched from a non-conductive state to a conductive state according to the first aspect of the present invention. When the time is switched to the above, the measured output stabilization time and the standard output stabilization time are obtained from the time required until the output fluctuation after the start of energization reaches within 0.2 mV / sec. When the output stabilization time exceeds 1.5 times, it is to diagnose that the semiconductor gas detection element to be diagnosed is deteriorated.

Furthermore, as described in claim 3, in the invention of claim 1, when the semiconductor gas detection element to be diagnosed is switched from a non-energized state to an energized state,
If the time required for the output fluctuation after the start of energization to reach within 0.2 mV / sec exceeds 15 seconds, it is to diagnose that the semiconductor gas detection element to be diagnosed has deteriorated.

[Function and Effect 2] In performing the diagnostic method described in the above-described function and effect 1, when it is clear that many semiconductor gas sensing elements exhibit similar behavior, the standard output stabilization time serving as a reference for diagnosis is obtained. Is given as a numerical value, and it can be considered that the presence or absence of the deterioration can be determined by comparing the output stabilization time twice as long as the predetermined value with the actual measured output stabilization time. If the time until the output fluctuation at the beginning of energization reaches within 0.2 mV / sec is used as the output stabilization time, the initial output can be regarded as having been stabilized with good reproducibility. The output stabilization time is measured based on this output stability criterion, and the measured output stabilization time is 1.5 times the standard output stabilization time.
By judging the presence or absence of deterioration based on whether the number exceeds twice, it is possible to objectively and clearly diagnose the degree of deterioration of the semiconductor gas detection element to be diagnosed. it is conceivable that.

As shown in the embodiment described later, the standard output stabilization time measured at the second energization of the non-degraded semiconductor gas sensing element (1) in FIG. The measurement output stabilization time measured at the time of the second energization of the semiconductor gas detecting element of (2) and (3) in FIG. 6 to be measured is measured, and the degree of deterioration of the semiconductor gas detecting element to be diagnosed is determined. For this purpose, the value of the measured output stabilization time / standard output stabilization time is determined. As a result, in the measured output stabilization time of the semiconductor gas detection element of (2), the value of the ratio to the standard output stabilization time does not exceed the reference value of 1.5, so that the deterioration is considered to have occurred. Probably, but the degree of deterioration is considered to be minor. Further, in the measured output stabilization time of the semiconductor gas detection element of (3), the value of the ratio to the standard output stabilization time greatly exceeds the reference value of 1.5, so that the degree of deterioration is large. Conceivable.

That is, when the ratio of the measured output stabilization time / standard output stabilization time does not exceed 1.5, it is considered that the semiconductor gas detection element to be diagnosed has deteriorated, but the degree of deterioration is Since it is considered to be minor, it will be judged that it can be used by taking measures such as re-adjusting the zero span.Therefore, there is no need to replace it and it can be considered that it has not deteriorated in actual use. Absent. After readjustment, it has the same characteristics as a semiconductor gas detection element that has not deteriorated, and can be used continuously as it is not deteriorated. If the ratio of the measured output stabilization time / standard output stabilization time exceeds 1.5, the degree of deterioration of the semiconductor gas detection element to be diagnosed is large, and the semiconductor gas detection element that has not deteriorated is detected. Since it is considered that the element has characteristics different from those of the element, it is determined that the element needs to be replaced.

Further, the output fluctuation at the beginning of energization is 0.2 mV.
If the time required to reach within / sec is used as the output stabilization time, the initial output can be regarded as stabilized with good reproducibility. It is set to 15 seconds, and if the time exceeds 15 seconds, it is possible to diagnose only the objectively obtained time by diagnosing that the semiconductor type gas detection element to be diagnosed has deteriorated.

As described above, it has become possible to provide a method for diagnosing gas detection performance capable of making a judgment in accordance with the actual condition of a semiconductor gas detection element to be diagnosed.

That is, since the output stabilization standard for clarifying the output stabilization time and the standard of the measured output stabilization time / standard output stabilization time, which is a ratio for judging the presence or absence of deterioration, are set, it is generally used in actual use. Even a person can easily and quickly determine the degree of deterioration of the semiconductor gas detection element to be diagnosed.

[Structure 3] A feature of the present invention for achieving this object is that a semiconductor mainly composed of a metal oxide semiconductor provided so as to be capable of contacting a gas to be detected, as described in claim 4. In a gas detection device provided with a gas detection circuit capable of measuring a resistance value of the semiconductor type gas detection device by applying a gas detection voltage to the gas detection device, when re-energization is performed a plurality of times of energization is repeated. An output measuring mechanism for measuring the output stabilization time is provided.

[Effect 3] That is, a gas detection voltage is applied to a semiconductor gas detection element mainly composed of a metal oxide semiconductor provided so as to be in contact with the gas to be detected, and the semiconductor gas detection element is By providing a gas detection circuit capable of measuring a resistance value, it is possible to configure a gas detection device capable of obtaining an output based on a change in the resistance value from the gas detection element.

Further, since an output measuring mechanism for measuring an output stabilization time at the time of re-energization when a plurality of energizations are repeated is provided, the measured output stabilization time can be known. Therefore, the measured output stabilization time is compared with the standard output stabilization time or a reference threshold, and the measurement output stabilization time of the semiconductor gas detection element to be diagnosed can be easily measured even by a general user. This makes it possible to quickly diagnose the gas detection performance and determine whether it is necessary to replace the gas detection element with a semiconductor gas detection element that has not deteriorated.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. As shown in FIG. 1, the gas detection device of the present invention measures the resistance value of the semiconductor-type gas detection element 10 by applying a gas detection voltage to the semiconductor-type gas detection element 10. The semiconductor type gas detection element 10 is incorporated in a possible gas detection circuit 20 so as to be freely contacted with a gas to be detected. Further, when the resistance value of the semiconductor type gas detection element 10 changes, an output unit 3 that receives an electric signal based on the resistance value and generates an output.
0, and an output measuring mechanism 40 for measuring the output stabilization time during energization is provided.

As shown in FIG. 2, the semiconductor type gas sensing element 10 includes a noble metal wire 11 such as platinum, palladium, or a platinum-palladium alloy, and a metal oxide mainly containing a metal oxide such as tin oxide or indium oxide. It is possible to use a so-called hot-wire type semiconductor gas detecting element having a gas sensing portion 12 formed by applying a semiconductor, drying and then sintering. Further, the form of the semiconductor gas detecting element is not limited to the hot wire type, and various forms such as a substrate type can be applied.

The gas detecting circuit 20 includes a voltage detector 21 for measuring a change in resistance of the semiconductor gas detecting element 10.
And a resistance element (R1) 22, a resistance element (R2) 23, and a compensation resistance element (RL) 24. Here, the detection of the gas to be detected is performed by applying a gas detection voltage when detecting the gas to be detected in the atmosphere and measuring a change in the resistance value of the semiconductor gas detection element 10. Further, the resistance element (R1)
22, the resistance element (R2) 23, and the compensation resistance element (RL) 24 have known resistance values.
1) 22, the resistance element (R2) 23 is a fixed resistance, and the compensation resistance element (RL) 24 is a variable resistance. Here, the resistance value of the resistance element (R1) 22 is r1, the resistance value of the resistance element (R2) 23 is r2, the resistance value of the compensation resistance element (RL) 24 is rL, and the resistance of the semiconductor type gas detection element is Assuming that the resistance value is rS, the sensor output is V, and the bridge voltage is E, the sensor output is obtained by the following equation (1).

[0037]

V = −E {rS / (rS + rL) −r1 / (r1 + r2)}

The output unit 30 may be provided with an alarm device that receives an electric signal based on the resistance value of the semiconductor gas detection element 10 and issues an alarm output when the resistance value of the semiconductor gas detection element 10 changes. In place of the alarm output, a digital display of the measured density value may be used, or a composite output of these may be used.

The output measuring mechanism 40 starts to energize the gas detection element in conjunction with an arithmetic unit that calculates the degree of output attenuation per unit time based on the output from the gas detection circuit when energized. A timer or the like is provided to measure the output stabilization time until the degree of attenuation falls below a predetermined value. In addition, the power supply switching of the gas detection device when performing gas detection performance diagnosis can be manually controlled, but by incorporating a program or the like for automatic control, the output stabilization time is more easily obtained, This can be used for diagnosing deterioration of the gas detection element.

[0040]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 4 and 5 show the output (initial output) of a semiconductor gas detection element that has not deteriorated and a semiconductor gas detection element whose characteristics have changed after energization after one day of non-energization. The result of the comparison is shown. Among the semiconductor gas sensing elements that have been used in actual use and whose characteristics have changed, an embodiment using a semiconductor gas sensing element whose actual use period is 6 months and whose characteristic change is slightly deteriorated (deterioration degree is slight) will be described. FIG. 4 shows an embodiment using a semiconductor gas sensing element in which the actual use period is 2 years under the same use conditions as the above-mentioned semiconductor gas sensing element and the deterioration (large degree of deterioration) with a large characteristic change is recognized. FIG. 5 shows a comparison with a semiconductor gas detection element (normal) which has not deteriorated. The output measurement was performed for each of the semiconductor-type gas sensing elements at the first energization (first energization) after a one-day non-energization period and immediately after the power was turned off after the first energization. This was performed when the power was supplied (the second power supply). In both examples, the sensor output after 300 seconds is zero. The re-energization is usually set to be performed within a few seconds to 10 minutes after the initial energization.

It is known that the output characteristics of the semiconductor gas sensing elements having normal, slight degree of deterioration and large degree of deterioration have differences as shown in FIGS. 8 (a) and 8 (b). That is, FIG.
(A) is a graph comparing the output characteristics of the semiconductor type gas detection element having normal, slight deterioration, and large deterioration when 13A city gas is used as the gas to be detected. According to this graph,
Although the output characteristics of a normal semiconductor gas detection element and a semiconductor gas detection element with a small degree of deterioration do not change much,
It can be seen that the output characteristics of the semiconductor gas detection element having a large degree of deterioration are considerably different from those of the semiconductor gas detection element having a normal and small degree of deterioration. FIG. 8B shows H
₄ is a graph comparing output characteristics of a semiconductor gas detection element having a normal, a small degree of deterioration, and a large degree of deterioration when ₂ is a gas to be detected. According to this graph, the output characteristics of the semiconductor type gas sensing element is clearly different, particularly for deterioration degree is large semiconductor type gas sensing elements were found to significantly sensitized against H _2. The output was measured using each semiconductor type gas detection element having such output characteristics.

That is, in the initial output at the time of the first energization, it is possible to clearly distinguish the output (standard output) of the semiconductor gas detection element that has not deteriorated from the output of the semiconductor gas detection element whose characteristics have changed. On the other hand, in the initial output at the time of the second energization, the output of the semiconductor gas detection element whose characteristics have changed from the output of the semiconductor gas detection element that has not deteriorated is 1
The output level decreased earlier than the output at the time of the second energization, and exhibited a behavior similar to the standard output. Note that when the power is turned off after the output measurement after re-energization as the second energization, and the same measurement is performed again thereafter, that is, when the initial output is measured after the third energization, the above-described second time The same result as the initial output at the time of re-energization was obtained (not shown). This means that the behavior of the initial output of the semiconductor gas detection element does not change compared to the behavior of the initial output after the second or subsequent energization. That is, it is understood that only two times of energization are required when measuring the initial output of the semiconductor gas detection element.

From the above results, it is determined that the output has stabilized when the output fluctuation at the beginning of energization reaches 0.2 mV / sec, and the time required until the output stabilizes is defined as the output stabilization time. Under such conditions, the non-energization period is set to 0 to 20.
When the output stabilization time is set up to the day, (1) a semiconductor-type gas detection element that has not deteriorated (normal), (2) a semiconductor-type gas detection element that has a slight deterioration in the characteristic change (a degree of deterioration is small), ( 3) FIG. 6 shows the results of measuring the output stabilization time by an output measurement mechanism using a semiconductor gas detection element (deterioration is large), which is a deterioration having a large characteristic change.

That is, the standard output stabilization time of the semiconductor gas detection element (1) measured at the second energization is about 9 seconds. On the other hand, the measurement output stabilization times measured during the second energization of the semiconductor gas detection elements (2) and (3) to be diagnosed are about 13.5 seconds and about 36 seconds, respectively. These values are obtained when the non-energization period is one day. Here, the value of (measured output stabilization time / standard output stabilization time) was obtained to determine the degree of deterioration of the semiconductor gas detection element to be diagnosed. It was about 4.0. From FIG. 6, it is considered that the same value is obtained as the measured output stabilization time / standard output stabilization time even when the non-energization period is one day or more.

That is, in the measured output stabilization time of the semiconductor gas detection element of (2), the value of the ratio to the standard output stabilization time does not exceed the reference value of 1.5, so that the deterioration occurs. However, the degree of deterioration is considered to be minor. At this time, the semiconductor type gas sensing element can be continuously used by readjusting the zero span or taking measures according to the degree of deterioration.

Also, in the measured output stabilization time of the semiconductor type gas detection element of (3), the value of the ratio to the standard output stabilization time greatly exceeds the reference value of 1.5.
The degree of deterioration is large, and the H ₂ sensitivity is
It is considered to be in a state that cannot be used. At this time, it is necessary to replace the semiconductor gas sensing element with a semiconductor gas sensing element that has not deteriorated.

In this case, the output fluctuation at the initial stage of energization is 0.
The time required to reach 2 mV / sec is 13.5 seconds. Here, when the time until the output fluctuation at the beginning of energization reaches within 0.2 mV / sec is used as the output stabilization time,
The initial output can be regarded as stabilized with good reproducibility. In other words, by setting the output stabilization time to 15 seconds, it can be seen that if the output stabilization time exceeds 15 seconds, it is possible to diagnose that the semiconductor gas detection element to be diagnosed has deteriorated.

[Another Embodiment] Another embodiment will be described below. FIG. 7 shows an embodiment in which the power supply switching control of the gas detection device is performed by a built-in program at the time of gas detection performance diagnosis. As the semiconductor gas detecting element, a semiconductor gas detecting element that has not deteriorated (normal) and a semiconductor gas detecting element (deteriorated) whose characteristic change is recognized were used. In this control pattern, a voltage of 2.5 V is applied for 2 minutes during the initial energization, and the output stabilization time is measured during this time. 2 from energization
After a lapse of minutes, the power was turned off, and 10 seconds later, 2.5 V was applied again to re-energize the power. During this time, the output stabilization time was measured, and the power was turned off two minutes after the re-energization. The operation of the detection performance diagnosis ends. Based on the obtained results, it is determined whether or not the semiconductor gas detection element to be diagnosed has deteriorated and the degree of the deterioration.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a gas detection device of the present invention.

FIG. 2 is a schematic diagram of a semiconductor gas detection element.

FIG. 3 is a schematic diagram of a bridge circuit.

FIG. 4 is a graph (1) comparing initial outputs when power is supplied after a non-current supply period (1 day).

FIG. 5 is a graph (2) comparing initial outputs when power is supplied after a non-current supply period (1 day).

FIG. 6 is a graph comparing output stabilization times when power is supplied after a non-power supply period.

FIG. 7 is a graph illustrating a control pattern by a gas detection performance diagnosis program;

FIG. 8 is a graph comparing the output characteristics of a semiconductor type gas detection element having normal, minor degradation, and large degradation. (A) When 13A city gas is used as the detected gas (b) H ₂ is used as the detected gas If

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Semiconductor type gas detection element (S) 11 Noble metal wire 12 Gas sensing part 20 Gas detection circuit 21 Voltage detector 22 Resistance element (R1) 23 Resistance element (R2) 24 Compensation resistance element (RL) 30 Output part 40 Output measurement mechanism

Continued on the front page F-term (reference) 2G046 AA01 BA02 BA09 CA03 DC05 DC11 DC18 EB04 FB02 FE29 FE31 FE39 2G060 AF07 BA01 HA06 HC07 HC09 HC10 HC24

Claims (4)

[Claims] 1. A method for diagnosing gas detection performance of a semiconductor gas detection element comprising a metal oxide semiconductor as a main component, comprising:
Standard output stabilization time measured at re-energization after repeated de-energization switching, and multiple re-energization of semiconductor gas detection element to be diagnosed, measured at re-energization when de-energized switching is repeated And comparing the measured output stabilization time with the measured output stabilization time. If the ratio between the measured output stabilization time and the standard output stabilization time exceeds a predetermined value, it is diagnosed that the semiconductor gas detection element to be diagnosed has deteriorated. Gas detection performance diagnosis method. 2. The method according to claim 1, wherein when the semiconductor gas sensing element is switched from a non-energized state to an energized state, the measured output stabilization is determined by a time required until an output fluctuation after the energization starts reaches 0.2 mV / sec or less. A time and the standard output stabilization time are obtained, and when the measured output stabilization time exceeds 1.5 times the standard output stabilization time, it is diagnosed that the semiconductor gas detection element to be diagnosed is deteriorated. Item 2. The gas detection performance diagnosis method according to Item 1. 3. When the semiconductor gas detection element to be diagnosed is switched from a non-energized state to an energized state, the time required for the output fluctuation after the start of energization to reach within 0.2 mV / sec is 15 minutes. If the time exceeds two seconds, it is diagnosed that the semiconductor gas detection element to be diagnosed is deteriorated.
The gas detection performance diagnostic method according to the above. 4. A semiconductor-type gas detection element containing a metal oxide semiconductor as a main component and provided in contact with a gas to be detected,
A gas detection device provided with a gas detection circuit capable of measuring a resistance value of the semiconductor-type gas detection element by applying a gas detection voltage, wherein an output stabilization time at a time of re-energization when a plurality of energizations is repeated. A gas detection device provided with an output measurement mechanism for measuring pressure.