JP4495563B2 - Alarm - Google Patents

Description

  The present invention relates to an alarm device, and more particularly, to an alarm device that detects and alerts a target gas using a gas sensor having a predetermined temperature dependency.

  An alarm device that performs an alarm operation by compensating for the temperature dependence of the gas sensor is well known in Patent Document 1 below. This type of alarm is a gas sensor that detects the target gas and outputs a sensor signal, a temperature sensor that detects the ambient temperature and outputs a temperature signal corresponding to this, a temperature dependency from the sensor signal based on the temperature signal And a processing unit for generating an alarm signal and an alarm unit for receiving the alarm signal.

Specifically, the memory included in the processing unit stores the relationship between the ambient temperature and the temperature-dependent compensation coefficient, which is known in advance in the gas sensor included in the alarm device, for example, as illustrated in FIG. ing. The current ambient temperature is calculated from the temperature data obtained from the temperature signal output from the temperature sensor, and the compensation coefficient corresponding to the ambient temperature is calculated with reference to the relationship between the ambient temperature and the compensation coefficient. . A sensor signal from which temperature dependency is removed is obtained using this compensation coefficient.
Japanese Utility Model Publication 5-64762

  In the alarm device described above, accurate ambient temperature detection is a prerequisite for accurately removing temperature dependence from the sensor signal. However, the temperature sensor employed in this type of alarm device must employ a large tolerance mainly from the viewpoint of cost, and if that is the case, the individual characteristics over the range shown in FIG. May vary. That is, according to the temperature sensor that is actually adopted for the temperature data corresponding to the ambient temperature as shown by the solid line in FIG. 7 by the ideal temperature sensor, the temperature sensor as shown by the dotted line in FIG. There is a high possibility that the temperature data varies due to individual differences. Note that the temperature data in FIG. 7 is, for example, a resistance value of a temperature sensor, or a current value or a voltage value corresponding thereto.

  Therefore, the compensation coefficient also varies depending on the individual temperature sensors over the range shown by D in FIG. 6, and eventually, the gas detection accuracy varies among the alarm devices. . In order to avoid this, an expensive temperature sensor with a small tolerance may be used for each alarm device, but this leads to an increase in cost.

  Therefore, in view of the present situation described above, the present invention has an object to provide an alarm device that can accurately compensate the temperature dependence of a gas sensor without using an expensive temperature sensor.

  The alarm device according to claim 1, which has been made to solve the above-mentioned problem, as shown in FIG. 1, uses a gas sensor 11 having a predetermined temperature dependence to detect and alarm a target gas. Compensation information storage means 23A for preliminarily storing compensation information for compensating the temperature dependence, a temperature sensor 13 for detecting an ambient temperature and outputting a detection temperature signal corresponding thereto, and the reference temperature at the reference temperature The reference temperature data corresponding to the temperature signal to be originally obtained by the temperature sensor 13 is compared with the detected temperature data corresponding to the detected temperature signal output from the temperature sensor 13 at the reference temperature, which corresponds to the difference between the two data. Error temperature data generating means 22A for generating error temperature data to be corrected, and compensation information correcting means 22B for correcting the compensation information based on the error temperature data. Includes, to compensate for the temperature dependence of the gas sensor based on the modified the compensation information, characterized in that.

  According to the first aspect of the present invention, the temperature data corresponding to the reference temperature signal that should be originally obtained by the temperature sensor at the reference temperature is compared with the temperature data corresponding to the detected temperature signal that is actually output from the temperature sensor, Error temperature data corresponding to the difference between the two data is generated. Based on the error temperature data, compensation information for compensating for temperature dependence stored in advance is corrected. The temperature dependence of the gas sensor is compensated based on the corrected compensation information, and the target gas is detected and alarmed. Since the compensation information for compensating the temperature dependency of the gas sensor is corrected based on such error temperature data, it becomes possible to cancel the variation of the temperature sensor in software.

  As shown in FIG. 1, the alarm device according to claim 2, which has been made to solve the above-described problem, is the alarm device according to claim 1, wherein the compensation information storage unit 23 </ b> A uses the ambient temperature as the compensation information. The compensation information correction unit 22B uses the error temperature data to output the detected temperature data output corresponding to the current ambient temperature. The value of the temperature compensation coefficient is obtained at the current ambient temperature by modifying and applying to the function.

  According to the second aspect of the present invention, a function that changes the value of the temperature compensation coefficient in accordance with the change in the ambient temperature is stored as compensation information for compensating the temperature dependence of the gas sensor. The detected temperature data output corresponding to the current ambient temperature is corrected with the error temperature data and applied to the function, and the value of the temperature compensation coefficient at the current ambient temperature is obtained.

  According to the first aspect of the present invention, the temperature data corresponding to the reference temperature signal that should be originally obtained by the temperature sensor at the reference temperature is compared with the temperature data corresponding to the detected temperature signal that is actually output from the temperature sensor, Error temperature data corresponding to the difference between the two data is generated. Based on the error temperature data, compensation information for compensating for temperature dependence stored in advance is corrected. The temperature dependence of the gas sensor is compensated based on the corrected compensation information, and the target gas is detected and alarmed. Since the compensation information for compensating the temperature dependency of the gas sensor is corrected based on such error temperature data, it becomes possible to cancel the variation of the temperature sensor in software. Therefore, the temperature dependence of the gas sensor can be accurately compensated without using an expensive temperature sensor.

  According to the second aspect of the present invention, a function that changes the value of the temperature compensation coefficient in accordance with the change in the ambient temperature is stored as compensation information for compensating the temperature dependence of the gas sensor. The detected temperature data output corresponding to the current ambient temperature is corrected with the error temperature data and applied to the function, and the value of the temperature compensation coefficient at the current ambient temperature is obtained. Accordingly, the temperature dependence of the gas sensor can be accurately compensated at any ambient temperature without using an expensive temperature sensor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing a main part of an alarm device according to an embodiment of the present invention. As shown in FIG. 2, the alarm device 1 includes a detection unit 10 and a processing unit 20. Note that a power supply unit, an alarm unit, an operation unit, and the like, which are generally included in this type of alarm device, are omitted here.

  The detection unit 10 includes a gas sensor 11 and a detection resistor 12 and a temperature sensor 13 connected in series. The gas sensor 11 is, for example, a well-known metal oxide semiconductor sensor, which reacts methane gas, carbon monoxide gas, or the like with harmful gas, and gives a sensor signal corresponding to the gas to the processing unit 20. The gas sensor 11 has an inherent temperature dependency. A predetermined voltage Vc is applied to the gas sensor 11.

  The temperature sensor 13 is, for example, a well-known resistance temperature detector, thermistor, semiconductor sensor, or the like, and changes its resistance value according to the ambient temperature. This resistance value is output as a divided value of the voltage Vc from the connection point between the temperature sensor 13 and the detection resistor 12. This partial pressure value is given to the processing unit 20 as a detected temperature signal indicating the ambient temperature.

  On the other hand, the processing unit 20 includes an analog / digital conversion unit (A / D) 21, a microcomputer 22, and a storage unit 23. The A / D 21 converts the sensor signal and the detected temperature signal, which are analog signals respectively supplied to the input terminals RX1 and RX2, into digital signals that can be processed by the microcomputer 22, and outputs the digital signals.

  As is well known, the microcomputer 22 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (A Read / Write Memory as needed). The CPU executes various processes such as control according to the present embodiment in accordance with a program stored in the ROM. The RAM appropriately stores data, programs, and the like necessary for the CPU to execute various processes. The microcomputer 22 obtains sensor data compensated for temperature dependency using a compensation coefficient obtained by a processing procedure described later, compares this with predetermined reference data, and if necessary, indicates that fact. The alarm signal shown is output from the output terminal TX.

  The storage unit 23 is, for example, an EEPROM (Electrically Erasable and Programmable ROM), and stores at least reference temperature data and a temperature compensation coefficient (also simply referred to as a compensation coefficient). The reference temperature data is data corresponding to a temperature signal that should be originally obtained by the temperature sensor at a predetermined reference temperature. The reference temperature data is data obtained on average by a plurality of temperature sensors of the same type as the temperature sensor 13 included in the alarm device 10. For example, it is the average value of the resistance value and the corresponding current value and voltage value obtained by a plurality of temperature sensors of the same type as the temperature sensor 13 in the atmosphere of 20 ° C. Such reference temperature data is obtained in advance through a test or the like.

  The compensation coefficient is a coefficient for compensating the temperature dependence of the gas sensor. That is, the compensation coefficient is a coefficient for obtaining an equivalent sensor output within the practical range of the ambient temperature for the same concentration gas to be detected. For example, as shown in FIG. 5, the compensation coefficient may be expressed as a function whose value changes in accordance with a change in ambient temperature within a practical range, for example, −10 ° C. to 50 ° C. By functionalizing the compensation coefficient, the temperature dependence of the gas sensor can be accurately compensated without using an expensive temperature sensor at any ambient temperature within the practical range.

  The compensation coefficient is preferably made into a function as shown in FIG. 5, but a representative ambient temperature and a corresponding compensation coefficient may be assigned one-to-one. The compensation coefficient is also obtained in advance through a test or the like. The storage unit 23 corresponds to compensation information storage means in the claims.

  By correcting the sensor output actually obtained from the gas sensor 11 at a predetermined ambient temperature with such a compensation coefficient, it is possible to obtain a sensor output in which temperature dependency is compensated. In order to calculate the compensation coefficient accurately, it is assumed that the ambient temperature is accurately calculated. Therefore, the present invention is effective.

  A processing procedure according to this embodiment of the alarm device having such a hardware configuration will be described with reference to FIG. 3 and FIG. FIG. 3A and FIG. 3B are flowcharts showing a processing procedure according to an embodiment of the present invention. In particular, FIG. 3A is a flowchart regarding error temperature data generation, and FIG. 3B is a flowchart regarding compensation coefficient correction. FIG. 4 is a graph for explaining error temperature data according to an embodiment of the present invention. FIG. 5 is a graph showing a temperature-dependent compensation function according to an embodiment of the present invention.

  In step S101 in FIG. 3A, the microcomputer 22 acquires detected temperature data via the A / D 21 in the atmosphere under a predetermined reference temperature. The reference temperature is 20 ° C., for example. The detected temperature data is data relating to the temperature corresponding to the detected temperature signal output from the temperature sensor 13 in the atmosphere at the reference temperature, for example, a voltage value. Next, in step S <b> 102, the microcomputer 22 reads the reference temperature data from the storage unit 23. The reference temperature data is as described above, but the detected temperature data needs to be the same type. For example, if the detected temperature data is given as a voltage value, the reference temperature data needs to be a voltage value.

  Subsequently, in step S103, the microcomputer 22 compares the detected temperature data with the reference temperature data, and calculates error temperature data in step S104. The error temperature data is temperature data corresponding to the difference between the detected temperature data and the reference temperature data, as indicated by ± c in FIG. In step S105, the microcomputer 22 stores the error temperature data ± c in the storage unit 23 for post-processing. The processing procedure of the microcomputer 22 shown in FIG. 3A corresponds to the error temperature data generation means in the claims.

  Next, in step S201 of FIG. 3B, the microcomputer 22 acquires current temperature data via the A / D 21. The current temperature data is data relating to the temperature corresponding to the detected temperature signal output from the temperature sensor 13 under the current temperature, for example, a voltage value. In short, it is a voltage value indicating the current ambient temperature of the alarm device 10. The current temperature data also needs to be the same type as the reference temperature data, for example, a voltage value. Next, in step S202, the microcomputer 22 reads the stored error temperature data ± c from the storage unit 23, and in step S203, reads the compensation function a * x + b as shown in FIG.

  Subsequently, in step S204, the microcomputer 22 corrects the compensation coefficient. That is, the microcomputer 22 incorporates the error temperature data ± c in the compensation function a * x + b to obtain the compensation coefficient α. Supplementally, in FIG. 5, error temperature data ± c is included in the value x on the horizontal axis (x ± c), multiplied by the inclination a, and the initial value b is added to obtain the compensation coefficient α. As a result, a compensation coefficient in which variations in the temperature sensor 13 are corrected can be obtained.

  In step S205, the microcomputer 22 converts the sensor data regarding the sensor output given through the A / D 21 into sensor data in which the temperature dependency is compensated using the compensation coefficient obtained in step S204. As a result, sensor data can be obtained in which variations in the temperature sensor 13 are removed and the temperature dependence is accurately compensated. The processing procedure of the microcomputer 22 shown in FIG. 3B corresponds to the coefficient correction means in the claims.

  When the microcomputer 22 compares the compensated sensor data with predetermined reference data and determines that the gas concentration should be alarmed, for example, the microcomputer 22 outputs an alarm signal indicating the fact from the output terminal TX. . And it alerts | reports via the alarm part which is not shown in figure.

  As described above, according to the present embodiment, it is possible to provide an alarm device that can accurately compensate the temperature dependence of the gas sensor without using an expensive temperature sensor.

It is a block which shows the basic composition of the alarm device of this invention. It is a block which shows the principal part of the alarm device which concerns on one Embodiment of this invention. FIG. 3A and FIG. 3B are flowcharts showing a processing procedure according to an embodiment of the present invention. It is a graph for demonstrating error temperature data concerning one embodiment of the present invention. It is a graph which shows the compensation function of the temperature dependence which concerns on one Embodiment of this invention. It is a graph which shows the relationship between ambient temperature and a compensation coefficient. It is a graph for demonstrating the dispersion | variation in temperature data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Alarm device 10 Detection part 20 Processing part 11 Gas sensor 12 Detection resistance 13 Temperature sensor 21 Analog-digital conversion part 22 Microcomputer 23 Memory | storage part

Claims (2)

An alarm device that detects a target gas using a gas sensor having a predetermined temperature dependence and alarms the gas,
Compensation information storage means for storing in advance compensation information for compensating the temperature dependence;
A temperature sensor that detects the ambient temperature and outputs a corresponding detected temperature signal; and
The reference temperature data corresponding to the temperature signal that should be originally obtained by the temperature sensor at the reference temperature is compared with the detected temperature data corresponding to the detected temperature signal output from the temperature sensor at the reference temperature, and the difference between the two data Error temperature data generating means for generating error temperature data corresponding to
Compensation information correction means for correcting the compensation information based on the error temperature data,
Compensating temperature dependence of the gas sensor based on the corrected compensation information;
An alarm device characterized by that. The alarm device according to claim 1,
The compensation information storage means includes
As the compensation information, a function in which the value of the temperature compensation coefficient changes according to the change in the ambient temperature is stored,
The compensation information correction means includes
The detected temperature data output corresponding to the current ambient temperature is corrected with the error temperature data and applied to the function to obtain the value of the temperature compensation coefficient at the current ambient temperature.
An alarm device characterized by that.

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