JP2010085339A - Zero point adjustment method of gas sensor using contact combustion type gas detection element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct easily a temperature-dependent change of zero point with time. <P>SOLUTION: In the zero point correction method of gas sensor using a contact combustion type gas detection element including a gas detection means 10 detecting and outputting a difference output between a contact combustion type gas detection element 11 and a compensation element 12 compensating the temperature characteristics of the sensor, a temperature detection means 70 detecting an environmental temperature, a zero point calibration means 20 calibrating the zero point of the gas detection means, a zero point adjustment means 30 adjusting a temperature change of output after the zero point calibration, a concentration computing means 50, and a concentration display means 60, an adjustment coefficient is previously calculated from the relation between the temperature change of the contact combustion type gas detection element 11 and the amount of zero point change and is stored in a temperature adjustment coefficient computing means 40, and the adjustment is carried out based on the adjustment coefficient by the zero point adjustment means 30. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for adjusting drift of a zero point of a gas detection device using a detection unit that uses a difference as a detection signal by, for example, bridge-connecting a catalytic combustion type gas detection element and a temperature compensation element.

  In general, the sensing element and compensation element have individual differences in the resistance value at the reference temperature, so that the bridge connection is adjusted by adjusting the value of the reference resistance by bridge connection so that the reference resistance is opposite to the reference temperature. Thus, adjustment is made so that the detection output becomes zero in the zero gas state, that is, zero balance is achieved.

  Although the compensation element is used to correct the temperature dependence of the sensing element, even if the power consumption of each element, that is, the amount of heat generated is the same, the size, thermal conductivity, Due to the difference in emissivity of the surface, the detection signal at a predetermined concentration, for example, Oppm, changes, that is, drifts depending on the temperature of the environment. For this reason, drift is also reduced using a temperature detection element.

However, after many years of use, the gas sensing element is burned by the heat of the gas sensing element due to the heat of the gas sensing element, part of the product adheres, and the temperature resistance coefficient changes to, for example, 8 ppm / deg. Zero drift occurs.
For this reason, even if the zero point is calibrated in this state, the temperature change dependency of the zero point becomes larger than that in the initial stage, and there is a problem that the indication accuracy is lowered. In the example of FIG. 2, the temperature change dependency is 0 ppm / deg at the initial stage (point A), but after zero drift (point B), the temperature change dependency is 8 ppm / deg even if the zero point is calibrated (point C). Will remain.

  On the other hand, as a result of examining the relationship between the zero drift amount of the catalytic combustion type gas detection element of the same standard and the temperature change dependency of the zero point, it was found that there is a certain relationship as shown in FIG.

  The present invention has been made in view of such circumstances, and the object of the present invention is the relationship between the zero drift amount examined in advance and the temperature change dependency in a configuration having a temperature sensing element in addition to the compensation element. Based on the knowledge that it is possible to correct the temperature compensation coefficient from the equation or table, the change in temperature dependence of the zero point of the gas detection device using the catalytic combustion type gas detection element over time can be simplified. It is to propose a correction method.

  In order to achieve such a problem, in the present invention, a gas detection means for detecting a differential output between a catalytic combustion type gas detection element and a compensation element for compensating the temperature characteristic of the sensor, and an environmental temperature are detected. A temperature detection means, a zero point calibration means for calibrating the zero point of the gas detection means, a zero point correction means for correcting a temperature change of the output after the zero point calibration, a concentration calculation means, and a concentration display means In the zero point correction method of the gas detection device using the catalytic combustion type gas detection element, a correction coefficient is calculated in advance from the relationship between the temperature change and the zero point change amount, and is stored in the temperature correction coefficient calculation means. Correction is made by the correction coefficient by the point correction means.

  According to the present invention, even if the characteristics of the catalytic combustion type gas detection element change after the zero point adjustment, the zero drift caused by the temperature change is reduced based on the relationship between the temperature change amount specified in advance and the zero point change amount. It can be easily corrected.

Therefore, details of the present invention will be described below based on the illustrated embodiment.
FIG. 1 shows an embodiment of the present invention, in which a detection unit 10 has a catalytic combustion type gas detection element 11 and a compensation element 12 connected in series, and two reference sides on these opposite sides. The resistors 13 and 14 are connected to each other as a detection terminal, and a differential signal between the catalytic combustion type gas detection element 11 and the compensation element 12 is output as a detection signal.
Note that the terminals 15 and 16 are connected to a driving power source including a constant voltage source or a constant current source.

  The detection signal from the detection unit 10 is output to the zero point correction unit 30 after the zero point is adjusted at a predetermined time by the zero point calibration unit 20. The zero point correction means 30 corrects the temperature change at the zero point of the detection signal caused by the temperature change based on the signal from the temperature correction coefficient calculation means 40 described later, and the density display means via the density calculation means 50 Output to 60.

  The temperature correction coefficient calculation means 40 calculates a zero point change amount corresponding to the temperature change amount calculated by the zero point change amount calculation means 80 based on the temperature signal from the environmental temperature detection means 70.

  In this embodiment, when the zero point is initially corrected by the zero point calibration means 20 at the time of installation of the apparatus (point A in FIG. 2), the adjustment amount a at this time is stored in the zero point adjustment amount storage means 90. The The detection signal whose zero point has been corrected is converted into a density by the density calculating means 50 via the zero point correcting means 30, and is output to the density display means 60 and displayed as a density (FIG. 3).

  On the other hand, even if there is a temporary temperature difference due to differences in shape and surface properties between the catalytic combustion type gas detection element 11 and the compensation element 12 due to changes in the environmental temperature, the drift of the zero point associated with this will be detected The detection signal corresponding to the gas concentration is output after being corrected by the signal from the means 70.

  On the other hand, if a gas component adheres to the catalytic combustion type gas detection element 11 due to long-term use, the temperature resistance characteristic fluctuates, so the zero point cannot be corrected only with the signal from the environmental temperature detection means 70, and the zero point drift does not occur. It occurs, and the temperature change dependency of the zero point becomes larger than that in the initial state.

  When the zero point drift is confirmed and the user calibrates the zero point by the zero point calibration unit, the adjusted drift amount b is stored in the zero point adjustment amount storage unit 90. The temperature correction coefficient calculation means 40 is a zero point obtained in advance corresponding to the adjustment amount a + b (for example, 2000 ppm in terms of concentration) from the reference time (when the device is installed) to the current time (point B in FIG. 2). The temperature dependent amount (point C in FIG. 2) 8 ppm / deg is read out using a previously calculated relational expression or dictionary (FIG. 4).

  Based on the zero point temperature dependency amount (8 ppm / deg) from the temperature correction coefficient calculation means 40, the detection signal is corrected for the temperature dependency of the zero point by the zero point correction means 30, and converted into a concentration by the concentration calculation means 50. It is output to the density display means 60 and displayed as a density with the zero point corrected.

  As a result, even if the temperature of the catalytic combustion gas detection element 11 changes temporarily due to a rapid change in the environmental temperature, the zero point drift is automatically corrected.

  In the above-described embodiment, the detection signal is extracted from the connection point between the catalytic combustion gas detection element 11 and the compensation element 12, but a reference resistance is connected to each of the catalytic combustion gas detection element 11 and the compensation element 12. Even if the connection point is used as an output terminal of a detection signal, the same effect is obtained.

It is a block diagram which shows one Example of this invention. It is explanatory drawing which shows operation | movement of this invention. It is a flowchart which shows the operation | movement at the time of the initial stage of this invention. It is a flowchart which shows the operation | movement at the time of the zero drift generate | occur | produced of this invention. It is a diagram which shows the relationship between drift amount and temperature dependence.

Explanation of symbols

  10 Detector 11 Catalytic combustion gas detector 12 Compensator 13 and 14 Reference resistance

Claims (1)

A gas detection means that outputs a differential output between a catalytic combustion type gas detection element and a compensation element that compensates the temperature characteristic of the sensor, a temperature detection means that detects an environmental temperature, and a zero point of the gas detection means are calibrated. Zero of a gas detection device using a contact combustion type gas detection element comprising a zero point calibration means, a zero point correction means for correcting a temperature change of the output after the zero point calibration, a concentration calculation means, and a concentration display means In the point correction method,
A correction coefficient is calculated in advance from the relationship between the temperature change of the catalytic combustion type gas detection element and the amount of change in the zero point, stored in the temperature correction coefficient calculating means, and corrected based on the correction coefficient by the zero point correction means. A zero point adjustment method for a gas detection device using a catalytic combustion type gas detection element.

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