JP3382809B2 - Humidity sensor failure detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor failure detection apparatus suitable for use in an air conditioning control system. [0002] Relative humidity plays a fundamental role in moisture absorption / drying, which is the interaction between moisture (humidity) in air and substances. Therefore, measurement of relative humidity is important in quality control and energy saving in the drying process. Here, for the purpose of industrial humidity measurement, a relative humidity sensor using a polymer film (polymer film humidity sensor element) and an electronic hygrometer using the same are known. [0003] A polymer film humidity sensor element measures the relative humidity of the atmosphere from a change in dielectric constant caused by the absorption and release of water from the polymer film. Basically, the capacitor has the structure shown in FIG. 7, and the change in the dielectric constant of the polymer film 1-1 is measured as the change in the capacitance value of the capacitor. Electrodes 1-2, 1
-3 is an extremely thin metal deposition film, and the electrodes 1-2, 1
The polymer film 1-1 absorbs / releases water through -3. Now, assuming that the thickness of the polymer film 1-1 is d, the dielectric constant is ε, and the electrode area is S, the capacitance value C of the capacitor can be expressed by C = ε · (S / d). Here, since ε changes according to the change in the atmosphere and the relative humidity, if C is measured, ε can be measured, and as a result, the relative humidity can be measured. [0005] The polymer film humidity sensor element 1 has the moisture sensitive characteristics shown in FIG. The capacitance value at 0% RH is Co,
Assuming that the capacitance value at x% RH is Cx, Cx / Co is almost constant. That is, in the polymer film humidity sensor element 1, the capacitance value and the relative humidity are proportional. Electronic hygrometers using the polymer film humidity sensor element 1 include a portable sensor, a wall-mounted sensor, and a flange sensor. The air-conditioning control system performs humidity control in addition to control of supply air temperature. FIG. 9 is a diagram showing a main part of the outside air processing air conditioner. In the figure, 2 is an insertion type temperature detector, 3 is an insertion type dew point temperature detector, 4 is a temperature controller, 5 is a humidity controller, 6-1, 6-2 and 6-3 are motor drivers, 7- 1, 7-2 are motor valves, 7-3 is a mod roll motor, 8 is a damper actuator, 9 is a cooling coil, 10 is a heating coil, 11 is a humidifying spray, and 12 is a blower. In this outside air processing air conditioner, a flange type electronic hygrometer is used as the insertion type dew point temperature detector 3, and the output value from the insertion type dew point temperature detector 3 (to the sensor signal from the polymer membrane humidity sensor element 1) The corresponding output value is supplied to the humidity controller 5, and the steam from the humidifying spray 11 is controlled so that the supply air from the blower 12 becomes the set dew point temperature (set value). However, according to the air conditioning control system using such an insertion type dew point temperature detector (hereinafter, simply referred to as a dew point temperature detector) 3, the dew point temperature detector 3 The polymer film humidity sensor element 1 easily deteriorates in a bad environment (high temperature, dew condensation, chemicals, etc.), and when it deteriorates, the electric capacity decreases rapidly. In the humidity controller 5, whether the decrease in the electric capacity of the polymer film humidity sensor element 1, that is, the decrease in the output value from the dew point temperature detector 3 is due to the deterioration of the polymer film humidity sensor element 1, It is hard to tell if it is due to a drop. For this reason, when the polymer film humidity sensor element 1 has deteriorated, that is, when the polymer film humidity sensor element 1 has failed to the low humidity side, the humidity controller 5 regards that the actual humidity has decreased, and The steam from the humidifying spray 11 is controlled so as to match the set value. FIG. 10A shows the on / off operation of the humidifying spray 11, and FIG. 10B shows the change of the output value (detection value) with respect to the set value. Assuming that the polymer film humidity sensor element 1 breaks down on the low humidity side at the point t1 shown in the drawing, the humidification spray 11 continues to be turned on due to the decrease in the output value, and the humidification operation continues. This allows
The interior of the room receiving the supply of air from the blower 12 becomes highly humid, and dew condensation occurs on walls and the like, causing problems such as water drops from the walls and ceiling and spots. For example, in an environment where a large amount of chemicals are used, such as a clean room, a hospital, or an operating room, the polymer film humidity sensor element 1 is likely to be deteriorated, which often leads to failure. If dew condensation occurs in such a place, there is a fear that a failure of precision equipment or a problem of hygiene may occur, and prevention of excessive humidification is desired.
In the above description, the polymer film humidity sensor element has been described as an example, but any humidity sensor element (ceramic humidity sensor element, lithium chloride humidity sensor element, etc.)
However, when a failure occurs on the low humidity side, the same problem as described above occurs. SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to prevent excessive humidification when a humidity sensor fails in a low humidity side in, for example, an air conditioning control system. It is an object of the present invention to provide a humidity sensor failure detection device which can be used. [0011] In order to achieve such an object, the present invention provides a minimum value and a minimum value which are not normally output.
The large value is stored in the storage means, and is stored in the storage means.
A failure on the low humidity side of the humidity sensor is detected by comparing with the minimum value, and when a failure is detected, the output of the output value indicating the humidity detected by the humidity sensor is stopped , Write to the storage means instead of the output value
The stored maximum value is transmitted .
According to the present invention, when the humidity sensor fails on the low humidity side, control according to the maximum value that is not normally output is performed.
Become like Hereinafter, the present invention will be described in detail based on embodiments. FIG. 2 is a block diagram showing a main part of a humidity sensor failure detection device according to an embodiment of the present invention. This device is incorporated inside the dew point temperature detector 3 shown in FIG. 9 together with its basic functions. In FIG. 1, 3-1 is a CPU, 3-2 is a RAM, 3-3 is a ROM, 3-4 is an input interface, and 3-5 is an output interface. The sensor signal from the polymer film humidity sensor element 1 is given to the CPU 3-1 via the input interface 3-4. CPU3
As a basic function, -1 obtains an output value corresponding to a sensor signal from the polymer film humidity sensor element 1 and sends it out via the output interface 3-5. [First Embodiment] FIG. 1 is a flowchart showing a characteristic operation of the dew point temperature detector 3. C
The PU 3-1 performs initialization (step 10).
1) The sensor signal from the polymer film humidity sensor element 1 is A
/ D conversion (step 102). Then, the sensor signal (humidity data) after the A / D conversion is compared with the minimum value (0% RH) and the maximum value (120% RH) stored in the ROM 3-3 (step 103). If the humidity data is between the minimum value and the maximum value (sections T1 to T2 shown in FIG. 3), the humidity data is D / A converted together with the temperature data to obtain an output value (step 104). Send it out via interface 3-5. After transmitting the output value, the process returns to step 102. If it is normal, the humidity data obtained in step 102 includes 12% from 0% RH including an error in accuracy.
It is in the range of 0% RH. Thereby, the processing operations of steps 102 to 104 are normally repeated. Here, it is assumed that the polymer film humidity sensor element 1 has deteriorated, that is, the polymer film humidity sensor element 1 has failed on the low humidity side. In this case, the electric capacity of the polymer film humidity sensor element 1 rapidly decreases, and the humidity data obtained in step 102 becomes 0% RH or less. Then, Step 10
In 3, the humidity data is 0% RH or less, that is, minimum value ≧ humidity data. As a result, the CPU 3-1 fixes the humidity data to the maximum value (step 105). In other words, instead of the humidity data, the maximum value used as the comparison reference value in step 103 instead of the humidity data should be a value that should be originally a value of 0% RH or less according to the sensor signal from the polymer film humidity sensor element 1. 120% RH) is defined as humidity data. Then, the humidity data is D / A converted into an output value (step 104), and transmitted through the output interface 3-5. Accordingly, when the polymer film humidity sensor element 1 fails to the low humidity side, an output value as if the humidity data from the polymer film humidity sensor element 1 is 120% RH is sent to the humidity controller 5. Can be As a result, the humidifying spray 11 is not kept on, and excessive humidification is prevented. [Embodiment 2] FIG. 4 shows a dew point temperature detector 3.
9 is a flowchart showing another example of the characteristic operation in FIG. The CPU 3-1 performs the initial setting (step 4).
01), A / D conversion of a sensor signal from the polymer film humidity sensor element 1 is performed (step 402). Then, the sensor signal (humidity data) after the A / D conversion is compared with the first comparison reference value (5% RH) and the second comparison reference value (10%) stored in the ROM 3-3.
0% RH) (step 403), and if the humidity data is between the first comparison reference value and the second comparison reference value (sections T1 and T2 shown in FIG. 5), the humidity data is D /
A conversion is performed to obtain an output value (step 404), which is transmitted through the output interface 3-5. After transmitting the output value, the process returns to step 402. In step 403, when the humidity data is 5
If not between% RH and 100% RH, step 40
Go to 5. In step 405, the CPU 3-1
The humidity data and the minimum value (0
% RH) and the maximum value (120% RH).
If the humidity data is between the minimum value and the maximum value (sections T0 to T1, T2 to T3 shown in FIG. 5), the process proceeds to step 406. In step 406, the CPU 3-1
Indicates whether the humidity data is 5% RH or less, that is, the section T
Check whether it is at 0 to T1. If the humidity data is in the sections T0 to T1, the humidity data is fixed at 5% RH (step 407). If the humidity data is not in the section T0 to T1, that is, if it is in the section T2 to T3, the humidity data is fixed to 100% RH (step 408). Then, the humidity data is D / A converted and output as an output value (step 404), and transmitted via the output interface 3-5. If it is normal, the humidity data obtained in step 402 is calculated from 0% RH to 12
It is in the range of 0% RH. In this embodiment, if the humidity data is between 0% RH and 5% RH,
When it is in the range of% RH to 120% RH, the humidity data is fixed to 5% RH and 100% RH, respectively, assuming that the error data is within the error range in accuracy. Thus, the processing operations of steps 402 to 408 are normally repeated. Here, it is assumed that the polymer film humidity sensor element 1 has deteriorated, that is, the polymer film humidity sensor element 1 has failed to the low humidity side. In this case, the electric capacity of the polymer film humidity sensor element 1 rapidly decreases, and the humidity data obtained in step 402 becomes 0% RH or less. Then, step 40
In 5, the humidity data is 0% RH or less, that is, minimum value ≧ humidity data. As a result, the CPU 3-1 fixes the humidity data to the maximum value (step 409). In other words, instead of the humidity data, the maximum value used as the comparison reference value in step 405 instead of the humidity data should be a value of 0% RH or less in accordance with the sensor signal from the polymer film humidity sensor element 1. 120% RH) is defined as humidity data. Then, the humidity data is D / A converted to an output value (step 404) and sent out via the output interface 3-5. Accordingly, when the polymer film humidity sensor element 1 fails to the low humidity side, an output value as if the humidity data from the polymer film humidity sensor element 1 is 120% RH is sent to the humidity controller 5. Can be As a result, the humidifying spray 11 is not kept on, and excessive humidification is prevented. Note that even when the humidity data obtained in step 402 becomes 120% RH or more, the CPU 3-1
Proceeds to step 409 in response to NO in step 405, and fixes the humidity data at that time to the maximum value. A failure of the dew point temperature detector 3 can be known on the humidity controller 5 side from the humidity data attached to the maximum value, that is, an output value corresponding to 120% RH which is not normally output. In the first and second embodiments, the dew point temperature detector 3
Although the humidity sensor inside is a polymer film humidity sensor element, it goes without saying that a ceramic humidity sensor element, a lithium chloride humidity sensor element, or the like may be used. In the first and second embodiments, all the failure detection devices are incorporated in the dew point temperature detector 3, but a part or all of the failure detection device may be provided on the humidity controller 5 side. In the first and second embodiments, the CPU 3
Although described as one processing operation, a similar processing function can be obtained by a hardware configuration. FIG. 6 illustrates a hardware configuration when the humidity sensor is a lithium chloride humidity sensor element. In the figure, 1 'is a lithium chloride humidity sensor element, 3-6 is a hybrid IC (HIC), 3-7 is a comparator, 3-8 is a switch circuit, 3-9 is an output circuit, and R1 to R4 are resistors. . The sensor signal from the lithium chloride humidity sensor element 1 'is provided to the HIC 3-6. The HIC 3-6 outputs an output voltage V1 corresponding to the sensor signal from the lithium chloride humidity sensor element 1 '. This output voltage V1 is applied to comparator 3-7 and switch circuit 3-8. The comparator 3-7 compares the output voltage V1 with a predetermined value (minimum value) VL defined as a divided voltage of the resistors R1 and R2. If V1 is equal to or higher than VL, the “H” level is set to VL.
If below, the output of the “L” level is switched to the switch circuit 3-8.
Send to The switch circuit 3-8 includes a comparator 3-
When an "H" level signal is given from 7, the switch S1 is turned on and the switch S2 is turned off. Accordingly, when the output voltage V1 is higher than VL, that is, when the lithium chloride humidity sensor element 1 'has not failed to the low humidity side, the output voltage V1 from the HIC 3-6 passes through the switch circuit 3-8, It is sent out via the output circuit 3-9. On the other hand, when an "L" level signal is given from the comparator 3-7, the switch circuit 3
-8 turns off the switch S1 and turns on the switch S2. As a result, when the output voltage V1 becomes lower than VL, that is, when the lithium chloride humidity sensor element 1 'fails to the low humidity side, the divided voltage of the resistors R3 and R4 replaces the output voltage V1 from the HIC 3-6. VH (maximum value) is passed through the switch circuit 3-8 and sent out via the output circuit 3-9. As is apparent from the above description, according to the present invention, when a failure on the low humidity side of the humidity sensor is detected, control according to the maximum value which is not normally output is performed.
Came to be, for example, in the air conditioning control system,
It is possible to prevent excessive humidification when the humidity sensor fails on the low humidity side.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart for explaining a specific processing operation (first embodiment) of a CPU in FIG. 2; FIG. 2 is a block diagram illustrating a main part of a humidity sensor failure detection device according to an embodiment of the present invention. FIG. 3 is a diagram showing a relationship between humidity data and an output value according to the first embodiment. FIG. 4 is a flowchart for explaining a specific processing operation (second embodiment) of the CPU in FIG. 2; FIG. 5 is a diagram showing a relationship between humidity data and an output value according to a second embodiment. FIG. 6 is a diagram illustrating a hardware configuration when a humidity sensor is a lithium chloride humidity sensor element. FIG. 7 is a diagram showing a basic structure of a polymer film humidity sensor element. FIG. 8 is a diagram showing the moisture sensitivity of a polymer film humidity sensor element. FIG. 9 is a diagram showing a main part of the outside air processing air conditioner. FIG. 10 is a time chart for explaining an operation at the time of failure of the polymer film humidity sensor element on the low humidity side. [Description of Symbols] 1 ... Polymer film humidity sensor element, 3 ... Insertion type dew point temperature detector, 3-1 ... CPU, 3-2 ... RAM, 3-3 ... RO
M, 3-4: input interface, 3-5: output interface.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 27/00-27/24 F24F 6/00-6/18 F24F 11/00-11/02 102

Claims (1)

(57) [Claims] [Claim 1] A minimum value and a maximum value which is not output normally.
Storage means for storing a fault detecting means for detecting a failure of the low humidity side of <br/> humidity sensor by comparing the minimum value stored in the storage means, a failure by the failure detecting means When detected, the output of the output value indicating the humidity detected by the humidity sensor is stopped , and the output value is stored in the storage unit instead of the output value.
And a signal processing means for sending the maximum value .