JP2005062199A - Calibration method for humidity sensor, and humidity sensor using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calibration method for a humidity sensor, capable of performing short-time and easy calibration in a measuring site installed with the humidity sensor, and to provide the humidity sensor used therefor, and the humidity sensor performing automatic calibration. <P>SOLUTION: In this calibration method for the humidity sensor S, by measuring humidity in three points at least having different temperature from each other, deriving a humidity calculation straight line from measured values thereof and correcting the measured values by use of the humidity calculation straight line, nonlinearity of the measured values by a detection part 1a of a humidity detection means 1 is dissolved. The humidity sensor S has linearity calibration means 13. The humidity calculation straight line is derived by the linearity calculation means 13 by use of the measured values of the humidity in the three points at least having the different temperature from each other, and the measured values are corrected by use of the humidity calculation straight line to dissolve the nonlinearity of the measured values by the detection part 1a of the humidity detection means 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a humidity sensor calibration method and a humidity sensor using the same. In more detail, humidity control for air conditioners, environmental testing machines, plant growing rooms, etc., dryers that monitor humidity, cookers, humidity detectors for vacuum cleaners, measurement records of humidity changes, and weather observation machines that perform authentication, radio The present invention relates to a calibration method of a humidity sensor used for a sound logger, a data logger for recording a state during product transportation, and a humidity sensor using the same.

  When a humidity sensor that measures and outputs humidity is continuously used for a certain period, it is inevitable that the measured value will be shifted. Therefore, it is necessary to calibrate the humidity sensor periodically.

  The conventional calibration method at the measurement site of the humidity sensor is to install the humidity sensor in a known humidity space and perform adjustment so that the measured value of the humidity sensor is correctly indicated. Realization of a space with a known humidity is achieved, for example, by putting a saturated salt or an unsaturated salt solution with a known concentration in a sealed container and allowing a sufficient time to pass, so that the atmosphere in the sealed container becomes stable. At this time, the humidity determined by the saturated salt or unsaturated salt solution to be used is a known space in the sealed container. Next, the humidity sensor is calibrated by placing the humidity sensor in the sealed container and adjusting the indicated value of the humidity sensor to the known humidity.

  In addition, calibration of the detection characteristics of the humidity sensor, that is, the slope of the humidity calculation line, is performed by calibrating at a plurality of humidity levels using a plurality of types of saturated salt or unsaturated salt solutions. In that case, if the temperature atmosphere is kept constant, more rigorous calibration can be performed.

  By the way, how often the calibration needs to be performed varies depending on the usage environment and the environmental resistance of the humidity sensor. In general, the longer the period of use, the greater the deviation. Therefore, it is better to calibrate frequently in order to maintain measurement accuracy.

  However, in order to calibrate, the measurement must be interrupted, and it takes time (about 0.5 to 6 hours) for the humidity atmosphere in the sealed container to stabilize, and the calibration work takes time and The work is complicated. It is also possible to calibrate by generating a reference humidity using a large-scale device such as a shunt-type humidity generation tank or a two-temperature two-pressure method, but for that purpose, the humidity sensor must be transported to the place where the equipment is located. There is a problem of not becoming.

  The present invention has been made in view of the problems of the prior art, and provides a humidity sensor calibration method and a humidity sensor used therefor that can be easily calibrated in a short time at a measurement site where the humidity sensor is installed. It is another object of the present invention to provide a humidity sensor that performs calibration automatically.

  The humidity sensor calibration method of the present invention measures humidity at least at three points with different temperatures, derives a humidity calculation line from these measurement values, and corrects the measurement value using the humidity calculation line, thereby adjusting the humidity. It is characterized in that the non-linearity of the measurement value by the detection unit of the detection means is eliminated.

  The humidity sensor of the present invention includes linearity calibration means, and the linearity calibration means derives a humidity calculation line using measured values of humidity at least at three points with different temperatures, and measures using the humidity calculation line. The value is corrected, and the non-linearity of the measurement value by the detection unit of the humidity detection means is eliminated.

  The humidity sensor of the present invention includes a failure diagnosing unit, and when the measured value exceeds a threshold by the failure diagnosing unit, the measured value deviates from a predetermined temperature / humidity profile, or the adjustment value by the calibration unit is If the threshold is exceeded, a failure may be diagnosed.

  According to the present invention, it is possible to obtain an excellent effect that measurement can be accurately performed from a low humidity region to a high humidity region.

  Hereinafter, although the present invention is explained based on an embodiment, referring to an accompanying drawing, the present invention is not limited only to this embodiment.

Embodiment 1
FIG. 1 shows a block diagram of a humidity sensor (hereinafter simply referred to as a humidity sensor) having a calibration function and a failure diagnosis function to which the humidity sensor calibration method according to Embodiment 1 of the present invention is applied. The humidity sensor S calibration method according to the first embodiment heats or cools the detection unit 1a of the humidity detection means 1, thereby correcting the indicated value of the humidity sensor so as to calibrate the humidity sensor S. If not done properly, it is configured to output a fault signal. That is, in the calibration method of the humidity sensor S of the first embodiment, the detection unit 1a is heated to a predetermined temperature to perform so-called zero point correction (zero point adjustment), while the detection unit 1a is condensed to generate so-called 100% R.D. H value correction (100% R.H value adjustment), zero adjustment and 100% R.H. The humidity sensor S is calibrated by correcting the slope of the humidity calculation line with the adjustment value in the H value adjustment.

  As shown in FIG. 1, the humidity sensor S includes a humidity detection unit 1 having a detection unit 1a that detects humidity in the atmosphere, and a temperature detection unit 2 that detects the temperature of the detection unit 1a of the humidity detection unit 1 or the vicinity thereof. And heating / cooling means 3 for heating the detector 1a of the humidity detecting means 1 to a predetermined temperature or cooling it to a predetermined temperature, an output means 4, and a controller / arithmetic unit 10 as main components.

  The detection unit 1a of the humidity detection means 1 is, for example, a ceramic or polymer impedance change type humidity detection element, a ceramic or polymer type capacity change type humidity detection element, and the like, and detects humidity in the atmosphere. .

  The temperature detection means 2 is a thermocouple, a temperature sensing element such as Pt100 and a thermistor, or a radiation thermometer, and is attached to the back surface of the detection portion 1a of the humidity detection means 1 or in the vicinity of the detection portion 1a of the humidity detection means 1. It is arrange | positioned and detects the temperature of the detection part 1a of the humidity detection means 1, or the temperature of the vicinity.

  The heating / cooling unit 3 is, for example, a heater / cooler configured by a resistance wire, a Peltier element, a heat pipe, and the like, and is disposed in the vicinity of the detection unit 1a of the humidity detection unit 1 to detect the detection unit 1a of the humidity detection unit 1. Is heated or cooled.

  Depending on the installation state of the humidity sensor S, the heating / cooling means 3 may be of a type in which the temperature in the atmosphere of the detection unit 1a of the humidity detection means 1 is changed by a constant temperature and humidity chamber.

  The output unit 4 displays the humidity measured by the humidity detection unit 1 and the temperature measured by the temperature detection unit 2 and displays a failure when the failure diagnosis unit 12 diagnoses the failure, for example, a digital display device Is done. Or it is set as the digital display apparatus with an alarm buzzer which sounds an alarm buzzer when a failure is diagnosed by the failure diagnostic means 12, for example.

  The control / arithmetic apparatus 10 includes a calibration unit 11 and a failure diagnosis unit 12, and controls the humidity detection unit 1, the temperature detection unit 2, the heating / cooling unit 3 and the output unit 4, and the calibration unit 11 includes The humidity sensor S is calibrated by correcting the measured value measured by the humidity detecting means 1, and the failure diagnosing means 12 determines the suitability of the calibration value by the calibrating means 11 and diagnoses the presence or absence of a failure. The control / arithmetic apparatus 10 having such a function is realized, for example, by storing a program corresponding to the function in a microcomputer.

  Next, automatic calibration and automatic failure diagnosis in the humidity sensor S having such a configuration will be described.

  (1) When a predetermined time has elapsed from the start of measurement, the control / arithmetic unit 10 instructs the heating / cooling means 3 to start heating to a predetermined temperature, that is, a predetermined temperature.

  (2) The heating / cooling means 3 starts heating the humidity detecting means 1 in accordance with an instruction from the control / arithmetic apparatus 10.

  (3) When the measured value of the temperature detection unit 2 reaches a predetermined temperature, the control / arithmetic unit 10 instructs the calibration unit 11 to start calibration and instructs the heating / cooling unit 3 to maintain the temperature.

  (4) The calibration unit 11 calibrates the humidity sensor S in response to a calibration start instruction from the control / arithmetic apparatus 10. The calibration by the calibration means 11 is performed by, for example, changing the measured value of the humidity detection means 1 at that time to 0% R.D. The correction is made to H, and the measurement value / humidity conversion table data stored in the memory of the control / arithmetic apparatus 10 is updated accordingly. Alternatively, as shown in FIG. 2, when the detection circuit of the humidity detection means 1 has a variable capacitor 1b and a variable resistor 1c, for example, the capacitance of the variable capacitor 1b is adjusted and the measured value is set to 0% R.P. By adjusting to H. Thereby, the indication value of the humidity sensor S is 0% R.D. Adjusted to H. That is, the zero point adjustment of the humidity sensor S is performed. When this calibration is completed, the control / arithmetic unit 10 instructs the heating / cooling means 3 to stop heating.

  (5) The control / arithmetic unit 10 instructs the heating / cooling unit 3 to start cooling to a predetermined temperature, that is, a predetermined temperature after a predetermined time has elapsed since the heating / cooling unit 3 stopped heating.

  (6) The heating / cooling means 3 starts cooling the humidity detecting means 1 in response to a cooling start instruction from the control / arithmetic apparatus 10.

  (7) When the measured value of the temperature detecting means 2 reaches a predetermined temperature, the control / arithmetic apparatus 10 instructs the calibration means 11 to start calibration and instructs the heating / cooling means 3 to maintain the temperature.

  (8) The calibration unit 11 calibrates the humidity sensor S according to the calibration start instruction from the control / arithmetic apparatus 10. The calibration by the calibration means 11 is performed by, for example, measuring the measured value of the humidity detection means 1 at that time by 100% R.D. The correction is made to H, and the measurement value / humidity conversion table data stored in the memory of the control / arithmetic apparatus 10 is updated accordingly with the zero point data fixed. Further, by making such an update, the slope of the humidity calculation line is also corrected at the same time. Alternatively, as shown in FIG. 2, when the detection circuit of the humidity detection means 1 has a variable capacitor 1b and a variable resistor 1c, for example, the resistance value of the variable resistor 1c is adjusted to set the measured value to 100% R. . By adjusting to H. Thereby, the indication value of the humidity sensor S is 100% R.D. Adjusted to H. That is, 100% R.D. The H value is adjusted. In addition, when the measured value fluctuates significantly when dew condensation is caused in the humidity detecting means 1, the measured value immediately before or after the dew condensation is used.

  (9) If the measured value of the humidity detecting means 1 after the calibration by the calibrating means 11 exceeds the threshold value, the failure diagnosing means 12 deviates from the preset temperature / humidity profile. If the adjustment value by the calibration means exceeds the threshold value, an alarm indicating that the humidity sensor S has failed is output.

  As described above, according to the first embodiment, calibration and failure diagnosis of the humidity sensor can be performed automatically and in a short time at the measurement site where the humidity sensor is installed. In the above description, the calibration is made after a predetermined time has elapsed from the start of the measurement, but the calibration is started when the measured value of the humidity detecting means 1 deviates from the preset temperature / humidity profile. You may make it do.

Embodiment 2
FIG. 3 shows a block diagram of a humidity sensor having a calibration function to which the humidity sensor calibration method according to Embodiment 2 of the present invention is applied (hereinafter simply referred to as a humidity sensor). In FIG. 3, the same reference numerals as those in FIG. 1 denote the same or similar components.

  In the calibration method of the humidity sensor S1 according to the second embodiment, the measurement of the low humidity region and the high humidity region can be accurately performed in the use of the humidity sensor, but the measurement is performed such that the measurement is higher or lower than the actual measurement in the middle humidity region. The linearity of the value may be lost. Therefore, in the second embodiment, as shown in FIG. 3, the humidity sensor S <b> 1 is calibrated by providing the linearity calibration means 13 in the control / arithmetic apparatus 10 to linearize the measured value.

The linearity calibration means 13 has a function of deriving a humidity calculation straight line by appropriately calculating the measured values of humidity at at least three points at different temperatures. For example, as shown in FIG. 4, if the measured values of humidity at temperatures t ₁ , t ₂ , and t ₃ are U ₁ , U ₂ , and U ₃ , these three values are appropriately processed to calculate the humidity. A straight line is derived. The calculation process for deriving the humidity calculation line includes, for example, a derivation method by a least square method, but is not limited to this, and various known line derivation methods can be used. The linearity calibration means 13 having such a function is realized by storing a program corresponding to the control / arithmetic apparatus 10.

  As described above, according to the second embodiment, the linearity calibration unit 13 is provided to derive the humidity calculation line from the required number of measurement values, and the measurement value is linearized using the straight line. Since the non-linearity is eliminated and the humidity sensor S1 is calibrated, measurement can be performed with high accuracy from a low humidity region to a high humidity region. Further, the calibration can be easily and quickly performed at the measurement site where the humidity sensor S1 is installed. In addition, a better result is obtained by the combined use with the first embodiment.

Embodiment 3
A schematic diagram of a humidity sensor (hereinafter simply referred to as a humidity sensor) having a calibration function to which the humidity sensor calibration method according to Embodiment 3 of the present invention is applied is shown in FIG. As shown in FIG. 2, a calibrator (calibration means) 20 for performing calibration by manual operation is provided instead of the control / arithmetic apparatus 10 of the first embodiment, and the temperature detection means 2 is a thermometer 2A, and heating / cooling is performed. The means 3 is a heater / cooler 3A. Further, the humidity detecting means 1 is configured such that a variable capacitor 1b is connected in parallel to the equivalent capacitance of the detecting unit 1a, and a variable resistor 1c is connected in series to an equivalent circuit of the detecting unit 1a.

  As shown in FIG. 5, the calibrator 20 includes a humidity display unit 21, a temperature display unit 22, a heater on / off switch 23, a cooler on / off switch 24, a variable capacity adjustment dial 25, a variable resistance adjustment dial 26, a control / calculation unit. 27 and a power switch 28. The power switch 28 can be any of various known switches.

  The humidity display unit 21 is, for example, a liquid crystal panel configured to instruct (display) the measured humidity.

  The temperature display unit 22 is, for example, a liquid crystal panel configured to indicate (display) the detected temperature.

  The heater on / off switch 23 and the cooler on / off switch 24 are, for example, push button switches. Although not clearly shown, the heater on / off switch 23 and the cooler on / off switch 24 are adjusted so as not to be turned on simultaneously.

  The variable capacitance adjustment dial 25 is a known dial that is capable of mechanically adjusting the capacitance of the variable capacitor 1b by rotating the dial.

  The variable resistance adjustment dial 26 is a known dial that can be mechanically adjusted by adjusting the resistance value of the variable resistance 1c by rotating the dial.

  The control / arithmetic unit 27 is, for example, a one-chip microcomputer, and controls the display of the humidity display unit 21, the display control of the temperature display unit 22, and the heater / cooler 3 </ b> A on by turning on / off the heater on / off switch 23. Off control, cooler on / off switch 24 is turned on / off to control the heater / cooler 3A cooler on / off. In addition, the gradient correction means 27a has an adjustment value at the time of zero adjustment and 100% R.D. Based on the adjustment value at the time of H value adjustment, the slope of the humidity calculation line is corrected. The function of the control / calculation unit 27 and the function of the gradient correction unit 27a are realized by storing programs corresponding to them in a one-chip microcomputer. The one-chip microcomputer also stores a program for performing processing necessary for calibration processing described later.

  Next, calibration of the humidity sensor S2 having such a configuration will be described.

  This calibration is performed using a calibration manual in which a calibration procedure, a predetermined heating temperature, a predetermined cooling temperature, and the like are described.

  (1) The power switch 28 is turned on, and the heating temperature and the cooling temperature are selected based on the humidity indicated on the humidity display unit 21 and the temperature indicated on the temperature display unit 22.

  (2) The heater on / off switch 23 is turned on to activate the heater of the heater / cooler 3A to heat the detector 1a.

  (3) When the display temperature (indicated value) of the temperature display unit 22 reaches a predetermined temperature (predetermined value), the variable capacitance adjustment dial (or variable resistance adjustment dial 26) 25 is operated to indicate the indicated value of the humidity display unit 21. 0% R.V. Adjust to H. That is, zero adjustment is performed. During this time, the control / calculation unit 27 controls the heating amount of the heater so that the heating temperature is maintained at a predetermined temperature.

  (4) The heater on / off switch 23 is turned off to stop heating by the heater.

  (5) When the display temperature of the temperature display unit 22 returns to the ambient temperature, the cooler on / off switch 24 is turned on to activate the cooler of the heater / cooler 3A to cool the detection unit 1a.

  (6) When the display temperature of the temperature display unit 22 reaches a predetermined temperature, the variable resistance adjustment dial (or variable capacitance adjustment dial 25) 26 is operated, and the indicated value of the humidity display unit 21 is set to 100% R.D. Adjust to H. That is, 100% R.D. Adjust the H value. During this time, the control / calculation unit 27 controls the cooling amount of the cooler so that the cooling temperature is maintained at a predetermined temperature.

  (7) The cooler on / off switch 24 is turned off to stop cooling by the cooler.

  (8) The gradient correction means 27a is provided with an adjustment value at the time of zero adjustment and 100% R.D. The slope of the humidity calculation line is corrected based on the adjustment value at the time of H value adjustment.

  (9) When the correction of the slope of the humidity calculation line by the slope correction means 27a is completed, the completion of calibration is displayed on the humidity display 21.

  (10) After confirming the display of calibration completion, the power switch 28 is turned off.

  Thus, according to the third embodiment, the humidity sensor S2 can be calibrated easily and quickly at the measurement site where the humidity sensor S2 is installed.

  Hereinafter, the present invention will be described in more detail with reference to more specific examples.

Example 1
Atmospheric temperature is 85 ° C. and relative humidity is 95% R.D. The zero point correction (zero point adjustment) in the case of H will be described. At that time, the water vapor partial pressure is 54994.6 Pa.

  The detector 1a is heated to a temperature at which the saturated water vapor pressure becomes sufficiently high, for example, the critical temperature of water 370.946 ° C. In this case, the saturated water vapor pressure is 22064 kPa. Therefore, the relative humidity of the detector 1a when heated to 370.946 ° C. is 0.25% R.D. H. Since the error of 0.25% does not cause a problem in normal measurement, when the detection unit 1a is heated to 370.946 ° C., the relative humidity is substantially 0% R.D. H. Therefore, the indication value of the humidity sensor S when the detection unit 1a is heated to 370.946 ° C., which is the critical temperature of water, is 0% R.D. By making the adjustment to H, zero correction (zero adjustment) of the humidity sensor S with respect to the atmosphere can be performed. That is, the offset of the indicated value can be eliminated and the humidity sensor S can be calibrated.

Example 2
The ambient temperature is 10 ° C. and the relative humidity is 30% R.D. 100% R.H. H value correction (100% RH value adjustment) will be described. In addition, the water vapor partial pressure at that time is 368.4 Pa.

  The detecting unit 1a of the humidity detecting unit 1 is cooled by the heating / cooling unit 3 to a temperature at which condensation occurs, for example, −40 ° C. The saturated vapor pressure of the detector 1a at that temperature is 12.84 Pa. Therefore, if the detection part 1a is cooled to the said temperature, dew condensation occurs reliably, and the relative humidity of the detection part 1a is 100% R.D. H. Therefore, the indication value of the humidity sensor S when the detection unit 1a is cooled to −40 ° C. is 100% R.D. By adjusting to H, 100% R.V. of the humidity sensor S with respect to the atmosphere. H value correction (100% RH value adjustment) can be performed. That is, the offset of the instruction value can be eliminated and the humidity sensor S can be calibrated.

  As mentioned above, although this invention has been demonstrated based on embodiment and an Example, this invention is not limited to this embodiment and an Example, A various change is possible. For example, in the first embodiment, the failure diagnosis unit is provided in the control / arithmetic apparatus. However, the failure diagnosis unit may be provided as necessary, and is not necessarily provided. In the first embodiment, the heating / cooling means is provided, but only the heating means or only the cooling means may be provided depending on the purpose of calibration.

  The present invention can be applied to various humidity sensors.

It is a block diagram of the humidity sensor to which the calibration method concerning Embodiment 1 of the present invention is applied. It is an equivalent circuit diagram of an example of the humidity detection means of the humidity sensor. It is a block diagram of the humidity sensor to which the calibration method concerning Embodiment 2 of the present invention is applied. It is a graph which shows the relationship between a measurement point and a derived line. It is a block diagram of the humidity sensor to which the calibration method concerning Embodiment 3 of the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Humidity detection means 1a Detection part 1b Variable capacitor 1c Variable resistance 2 Temperature detection means 2A Thermometer 3 Heating / cooling means 3A Heater / cooler 4 Output means 10 Control / calculation device 11 Calibration means 12 Fault diagnosis means 13 Linearity calibration means 20 Calibrator S Humidity sensor

Claims (3)

  By measuring the humidity at least at three points with different temperatures, deriving a humidity calculation line from these measurement values, and correcting the measurement value using the humidity calculation line, the non-linearity of the measurement value by the detection unit of the humidity detection means A humidity sensor calibration method characterized by eliminating the property. With linearity calibration means,
The linearity calibration means derives a humidity calculation line using measured values of humidity at at least three points at different temperatures, and the measurement value is corrected using the humidity calculation line and is measured by the detection unit of the humidity detection means. A humidity sensor characterized in that the non-linearity is eliminated. With fault diagnosis means,
The failure diagnosis means diagnoses a failure when the measured value exceeds a threshold, when the measured value deviates from a predetermined temperature / humidity profile, or when the adjustment value by the calibration means exceeds the threshold. The humidity sensor according to claim 2.

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