JP2017187328A - Capacitance type humidity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a shift in capacitance value.SOLUTION: A capacitance type humidity sensor comprises: a capacitance measurement unit 3 for measuring a capacitance value between the upper and lower electrodes of an element unit 1; a dew condensation determination unit 5 for determining whether the element unit 1 is in a dew condensed state; an inflection point detection unit 6 for making the capacitance value measured immediately after it is determined that the dew condensed state of the element unit 1 is resolved be a capacitance value at an inflection point on a relative humidity-capacitance value characteristic; a reference value calculation unit 7 for calculating a second reference value that is a capacitance value corresponding to 100%RH relative humidity at the current ambient temperature from a first reference value that is a capacitance value corresponding to 100%RH relative humidity when the current ambient temperature is at a reference temperature and the current ambient temperature; and a reference value update unit 9 for calculating, and updating to, the latest value of the first reference value from the capacitance value at the inflection point and the current ambient temperature when the capacitance value at the inflection point and the second reference value are different. The element unit 1 has a dew condensation detection structure for causing an inflection point to occur in the relative humidity-capacitance value characteristic.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a capacitive humidity sensor that measures relative humidity using a change in capacitance between electrodes of a sensor element unit in accordance with a change in humidity.

  When water droplets generated by condensation are in contact with the moisture sensitive film of a capacitive humidity sensor, depending on the contact conditions (contact time, ambient temperature, etc.) between the moisture sensitive film and the water droplet, structural changes such as swelling of the moisture sensitive film, Water molecules may remain at the film-substrate interface, and a capacitance value shift (hereinafter simply referred to as “shift”) at the same temperature and humidity may be observed after dew condensation is eliminated. In the capacitive humidity sensor, the relative humidity is obtained from the capacitance value between the electrodes arranged above and below the moisture sensitive film. Therefore, when the capacitance value is shifted, the relative humidity is also shifted. For example, when a capacitive humidity sensor is used for humidity measurement such as dew point measurement in an outside air duct, the sensor is required to be resistant to dew condensation, and is required to measure with high accuracy in a high humidity atmosphere.

  Conventionally, as a method of correcting the shift of the capacitance value, the chip is heated at regular intervals by a temperature sensor / heater arranged adjacent to the humidity sensor chip, and water molecules adhering to the moisture sensitive film, which cause the shift, are removed. There is a method of desorption (see Patent Document 1).

JP 2010-8318 A

  In the technique disclosed in Patent Document 1, heating cleaning is performed at regular intervals to recover the chip by heating the humidity sensor chip, but the shift of the capacitance value is corrected in the period until the next heating cleaning is performed. There was a problem that it was not possible.

  The present invention has been made to solve the above-described problem, and is capable of correcting the shift of the capacitance value even during the period when the heat cleaning is not performed, and the capacity capable of correcting the shift of the relative humidity to be measured. An object of the present invention is to provide a mold humidity sensor.

  The capacitive humidity sensor according to the present invention includes an element portion having a structure in which a moisture sensitive film is sandwiched between an upper electrode and a lower electrode, a capacitance measuring means for measuring a capacitance value between the upper electrode and the lower electrode, and the capacitance measuring means. The condensation measurement means for determining whether or not the element unit is in a dew condensation state based on the capacitance value measured by the method, and the capacitance measurement immediately after it is determined that the element unit is in a dew condensation state and the dew condensation state is eliminated. An inflection point detecting means that uses the capacitance value measured by the means as a capacitance value of an inflection point on the relative humidity-capacitance value characteristic, and a capacitance value corresponding to a relative humidity of 100% RH when the ambient temperature is the reference temperature And a second reference which is a capacity value corresponding to a relative humidity of 100% RH at the current ambient temperature from the first reference value and the current ambient temperature value. Reference value calculation means for calculating a value The comparing means for determining whether the capacitance value of the inflection point and the second reference value are different from each other, and the capacitance value of the inflection point and the second reference value are determined to be different from each other And a reference value update means for calculating the latest value of the first reference value from the capacity value of the inflection point and the current ambient temperature value and updating the value stored in the storage means. The element section has a dew condensation detection structure for generating the inflection point in the relative humidity-capacitance value characteristic.

Further, in one configuration example of the capacitive humidity sensor of the present invention, the storage unit stores in advance a capacitance value at the time of condensation, and the condensation determination unit is configured to determine the capacitance value measured by the capacitance measurement unit and the condensation time. It is characterized by determining whether the said element part is a dew condensation state by comparing with the capacitance value of this.
In the configuration example of the capacitive humidity sensor according to the present invention, the dew condensation detection structure may be configured such that the moisture sensitive film covers the lower electrode so that a part of the lower electrode is exposed on the surface of the element portion. It is characterized by comprising a notch part from which the part has been removed.
In the configuration example of the capacitive humidity sensor of the present invention, the dew condensation detection structure is provided on the moisture sensitive film and the upper electrode so that a part of the lower electrode is exposed on the surface of the element portion. It is characterized by comprising a plurality of openings.
Further, in one configuration example of the capacitive humidity sensor of the present invention, the dew condensation detection structure is formed to protrude from the upper electrode, and to protrude from the lower electrode. It consists of a 2nd protrusion part arrange | positioned so that 1 protrusion part and a gap may be opposed.

Further, in one configuration example of the capacitive humidity sensor according to the present invention, when the dew condensation determination unit determines that the dew condensation state is present, the measurement cycle of the capacity measurement unit is changed to a predetermined cycle shorter than a normal cycle. And a measurement cycle changing unit that returns the measurement cycle to a normal cycle after the condensation determination unit determines that the dew condensation state has been resolved and the inflection point detection unit detects the capacitance value of the inflection point. It is characterized by this.
Further, one configuration example of the capacitive humidity sensor according to the present invention further includes a relative humidity for obtaining a relative humidity based on the capacitance value measured by the capacitance measuring means, the first reference value, and the current ambient temperature value. A derivation unit is provided.
In addition, one configuration example of the capacitive humidity sensor of the present invention is further provided with a temperature sensor for measuring the ambient temperature.

  According to the present invention, the capacity measuring means, the dew condensation determination means, the inflection point detection means, the storage means, the reference value calculation means, the comparison means, and the reference value update means are provided, and further the inflection point in the relative humidity-capacitance value characteristic By providing the element portion with a dew condensation detection structure for causing the occurrence of the problem, the shift of the capacitance value can be corrected even during the period when the heat cleaning is not performed, and the shift of the relative humidity to be measured can be corrected.

It is a figure which shows the relative humidity-capacitance value characteristic in a capacitive humidity sensor. It is a block diagram which shows the structure of the capacitive humidity sensor which concerns on the 1st Embodiment of this invention. It is the top view and sectional drawing of the element part of the capacitive humidity sensor which concern on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the capacity | capacitance measurement part of the capacitive humidity sensor which concerns on the 1st Embodiment of this invention. It is a figure which shows the voltage-charge time characteristic between the upper and lower electrodes of the element part of the capacitive humidity sensor which concerns on the 1st Embodiment of this invention. It is a figure which shows a mode that the dew condensation produced in the element part of the capacitive humidity sensor which concerns on the 1st Embodiment of this invention. It is a flowchart explaining operation | movement of the capacitive humidity sensor which concerns on the 1st Embodiment of this invention. It is the top view and sectional drawing of the element part of the capacitive humidity sensor which concern on the 2nd Embodiment of this invention. It is a figure which shows a mode that the dew condensation produced in the element part of the capacitive humidity sensor which concerns on the 2nd Embodiment of this invention. It is the top view and sectional drawing of the element part of the capacitive humidity sensor which concern on the 3rd Embodiment of this invention. It is a figure which shows a mode that the dew condensation produced in the element part of the capacitive humidity sensor which concerns on the 3rd Embodiment of this invention. It is the top view and sectional drawing which show another structure of the element part of the capacitive humidity sensor which concerns on the 3rd Embodiment of this invention. It is the top view and sectional drawing of the element part of the capacitive humidity sensor which concern on the 4th Embodiment of this invention. It is a figure which shows a mode that the dew condensation produced in the element part of the capacitive humidity sensor which concerns on the 4th Embodiment of this invention. It is a block diagram which shows the structure of the capacitive humidity sensor which concerns on the 5th Embodiment of this invention. It is a flowchart explaining operation | movement of the capacitive humidity sensor which concerns on the 5th Embodiment of this invention.

[Principle of the Invention]
The capacitive humidity sensor is a sensor for obtaining relative humidity based on a capacitance value between upper and lower electrodes arranged above and below a moisture sensitive film and a reference value recorded and adjusted in advance. In a state where no condensation occurs on the electrodes, the relative humidity and the capacitance value of the sensor have a relationship as shown by the characteristic line 20 in FIG. 1, and the measured capacitance value becomes a predetermined capacitance value C100. The relative humidity is 100% RH. On the other hand, when water droplets generated by dew condensation adhere to the electrode, the apparent capacitance value increases due to the water droplets being charged, and a capacitance value C (corresponding to a relative humidity of 100% RH or more (100 + a)% RH. 100 + a). In FIG. 1, a relative humidity-capacitance value characteristic as indicated by a broken line 21 is generated.

  It is desirable that the amount of shift of the capacitance value can be corrected using the phenomenon as described above as a reference point at which the condensation of the capacitive humidity sensor is resolved and the normal humidity measurement can be returned. However, in the configuration of the conventional polymer capacitive humidity sensor, as shown by the characteristic lines 20 and 21 in FIG. 1, the slope of the relative humidity-capacitance value characteristic is almost constant, and the boundary between the condensation state and the condensation elimination cannot be distinguished. For this reason, it is not possible to determine the presence or absence of the shift of the capacitance value after the elimination of condensation.

  If a condensation sensor is separately installed, the presence or absence of water droplets can be detected, but even if a condensation sensor is provided, the presence or absence of water droplets on the humidity sensor cannot be directly known. That is, even if the dew condensation sensor is dry, water droplets may adhere to the humidity sensor, or even if the humidity sensor is dry, water droplets may adhere to the dew condensation sensor.

  Therefore, in the present invention, by adding a dew condensation detection structure to the element portion of the capacitive humidity sensor as will be described later, the relative humidity-capacitance value characteristic becomes a characteristic as shown by the characteristic line 22 in FIG. By generating an inflection point 23 in the humidity-capacitance value characteristic, it is possible to determine whether or not there is a shift in the capacitance value after eliminating condensation.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing the configuration of the capacitive humidity sensor according to the first embodiment of the present invention. The capacitive humidity sensor includes an element unit 1, a temperature sensor 2 disposed around the element unit 1, a capacitance measuring unit 3 that measures a capacitance value between the upper electrode and the lower electrode of the element unit 1, and an ambient temperature is Based on a storage unit 4 that stores in advance a first reference value that is a capacity value corresponding to a relative humidity of 100% RH at the reference temperature and a capacity value at the time of condensation, and a capacity value measured by the capacity measuring unit 3 A condensation determination unit 5 that determines whether or not the element unit 1 is in a dew condensation state, and a capacitance value that is measured by the capacitance measurement unit 3 immediately after it is determined that the element unit 1 is in a dew condensation state and this dew condensation state has been resolved. From the inflection point detection unit 6 that takes the capacitance value of the inflection point on the relative humidity-capacitance value characteristic, and the first reference value and the current ambient temperature value, the relative humidity at the current ambient temperature is 100% RH. Reference value calculation for calculating a second reference value that is a capacitance value corresponding to 7 and the comparison unit 8 that determines whether or not the capacitance value of the inflection point and the second reference value are different, and when it is determined that the capacitance value of the inflection point and the second reference value are different. A reference value update unit 9 that calculates the latest value of the first reference value from the capacitance value of the inflection point and the current ambient temperature value, and updates the value stored in the storage unit 4; And a relative humidity deriving unit 10 that obtains the relative humidity based on the capacitance value measured in Step 3, the first reference value, and the current ambient temperature value.

  In the configuration of FIG. 1, the temperature sensor 2 is provided inside the capacitive humidity sensor. However, the configuration is not limited to this, and the ambient temperature information is obtained from the temperature sensor provided outside the capacitive humidity sensor. You may make it acquire.

  FIG. 3A is a plan view of the element portion 1 of the present embodiment, and FIG. 3B is a cross-sectional view taken along the line II of FIG. The element unit 1 is arranged on the lower electrode 101 made of a plate-like conductor arranged on the substrate 100, the moisture sensitive film 102 made of a polymer arranged on the lower electrode 101, and the moisture sensitive film 102. An upper electrode 103 made of a plate-shaped conductor, electrode pins 104 and 105 for electrically connecting the electrodes 101 and 103 and the capacitance measuring unit 3, and electrode pins 104 and 105 and electrodes 101 and 103 The conductive paste 106 and 107 to be joined and a notch 108 (condensation detection structure) from which a part of the moisture sensitive film 102 covering the lower electrode 101 is removed so that a part of the lower electrode 101 is exposed. .

  FIG. 4 is a block diagram showing the configuration of the capacity measuring unit 3. The capacity measurement unit 3 includes a power supply 30, a resistor 31, a switch 32, a voltage detection unit 33, and a capacitance value calculation unit 34.

  When the capacitance value calculation unit 34 turns on the switch 32, a voltage is applied from the power supply 30 via the resistor 31 between the upper electrode 103 and the lower electrode 101 of the element unit 1, and the upper electrode 103, the moisture sensitive film 102, and the lower electrode are applied. 101 is charged, and the voltage between the upper electrode 103 and the lower electrode 101 changes as shown in FIG. In FIG. 5, 50 indicates the voltage between the upper and lower electrodes and the charging time characteristic at a relative humidity of 0% RH, and 51 indicates the voltage between the upper and lower electrodes and the charging time characteristic at a relative humidity of 100% RH.

  The charging time from when the voltage is applied between the upper electrode 103 and the lower electrode 101 to when the voltage between the upper electrode 103 and the lower electrode 101 reaches a predetermined threshold voltage TH is determined by the capacitance value C of the capacitor and the resistance 31. Since it is proportional to the known resistance value R, if the charging time is measured, the capacity value C can be obtained from this charging time. In FIG. 5, t0 indicates a charging time at a relative humidity of 0% RH, and t1 indicates a charging time at a relative humidity of 100% RH.

  The voltage detection unit 33 detects the voltage between the upper electrode 103 and the lower electrode 101 of the element unit 1. The capacitance value calculation unit 34 measures the charging time until the voltage between the upper electrode 103 and the lower electrode 101 reaches the threshold voltage TH from the detection result of the voltage detection unit 33, and the upper electrode 103 from the measurement result of the charging time. And a capacitance value C between the lower electrode 101 and the lower electrode 101 is calculated.

  On the other hand, as shown in FIG. 6, when a water droplet 109 generated by condensation adheres to the element unit 1 and the upper electrode 103 and the lower electrode 101 are conducted through the water droplet 109, a leakage current as shown in FIG. The capacitor charging time is extended. 5 indicates a voltage-charge time characteristic between the upper and lower electrodes when condensation occurs in the element unit 1, and t <b> 2 indicates a charging time when condensation occurs in the element unit 1. Thus, when the charging time is extended due to condensation, the capacitance value C appears to increase sharply as a result, and the inflection point as indicated by 23 in FIG. Produce. Further, when condensation is eliminated (at the time of disappearance of water droplets), the capacitance value C rapidly decreases and a similar inflection point is observed.

Next, a method of the present embodiment for correcting the shift of the capacitance value C after eliminating condensation using an inflection point will be described. FIG. 7 is a flowchart for explaining the operation of the capacitive humidity sensor according to the present embodiment.
First, the storage unit 4 includes a first reference value A, which is a capacitance value C corresponding to a relative humidity of 100% RH when the ambient temperature is the reference temperature, and a capacitance value C when condensation occurs in the element unit 1. (Cc in FIG. 1) is registered in advance. The first reference value A and the capacitance value Cc at the time of condensation can be obtained by a test performed in advance before the operation of the sensor.

As described above, the capacitance measuring unit 3 measures the capacitance value C between the upper electrode 103 and the lower electrode 101 of the element unit 1 for every predetermined measurement period (step S1 in FIG. 7).
The condensation determination unit 5 compares the capacitance value C measured by the capacitance measurement unit 3 with the capacitance value Cc at the time of condensation stored in the storage unit 4 in advance to determine whether the element unit 1 is in a condensed state ( FIG. 7 step S2). When the capacitance value C measured by the capacitance measuring unit 3 has reached the capacitance value Cc at the time of condensation, the condensation determination unit 5 determines that the element unit 1 is in a condensed state (YES in step S2).

Next, after determining that the element unit 1 is in the dew condensation state, the dew condensation determination unit 5 determines whether or not this dew condensation state has been eliminated (step S3 in FIG. 7). The dew condensation determination unit 5 determines that the dew condensation state of the element unit 1 has been eliminated when the capacitance value C measured by the capacitance measurement unit 3 is less than the capacitance value Cc at the time of dew condensation (YES in step S3).
The inflection point detection unit 6 sets the capacitance value C measured by the capacitance measurement unit 3 immediately after it is determined that the dew condensation state of the element unit 1 has been eliminated (step S4 in FIG. 7).

  Next, the reference value calculation unit 7 corresponds to the relative humidity 100% RH at the current ambient temperature from the first reference value A stored in advance in the storage unit 4 and the ambient temperature measured by the temperature sensor 2. A second reference value B, which is a capacitance value C, is calculated (step S5 in FIG. 7). The second reference value B is obtained by previously investigating the ambient temperature dependency (for example, temperature coefficient (F / ° C.)) of the relative humidity-capacitance value characteristic of the capacitive humidity sensor of the present embodiment and registering it in the storage unit 4. It is possible to calculate based on this ambient temperature dependency.

  The comparison unit 8 compares the capacitance value of the inflection point detected by the inflection point detection unit 6 with the second reference value B calculated by the reference value calculation unit 7, and compares the capacitance value of the inflection point with the second value. It is determined whether or not the reference value B is different (step S6 in FIG. 7). The difference between the capacity value of the inflection point corresponding to the actually measured value of the second reference value B and the second reference value B obtained from the calculation means that the capacity value has shifted after the condensation has been eliminated.

  When it is determined that the inflection point capacitance value and the second reference value B are different (YES in step S6), the reference value update unit 9 determines the inflection point capacitance value and the ambient temperature measured by the temperature sensor 2. From the temperature, the latest value of the first reference value A, which is the capacitance value C corresponding to the relative humidity 100% RH when the ambient temperature is the reference temperature, is calculated, and the first reference stored in the storage unit 4 is calculated. The value A is updated to the calculated latest value (step S7 in FIG. 7). The latest value of the first reference value A is that the capacitance value of the inflection point is regarded as the true value of the second reference value B, and the true value of the second reference value B and the ambient temperature measured by the temperature sensor 2 are It can be calculated using the value and the ambient temperature dependency of the relative humidity-capacitance value characteristic described above.

The reference value update unit 9 updates the first reference value A stored in the storage unit 4 when the inflection point capacitance value matches the second reference value B (NO in step S6). No (Step S8 in FIG. 7).
Thus, in this embodiment, the shift of the capacitance value can be corrected even during the period when the heat cleaning is not performed.

  When the relative humidity measured by the capacitive humidity sensor is X (% RH) and the capacitance value measured by the capacitance measuring unit 3 is C, the relative humidity X (% RH), the capacitance value C, the second reference value B, and the surroundings The relationship with the temperature is recorded in advance in a table (not shown) in the relative humidity deriving unit 10.

The relative humidity deriving unit 10 refers to the table every time the capacitance value C is measured by the capacitance measuring unit 3, and the value of the ambient temperature measured by the capacitance value C, the second reference value B, and the temperature sensor 2. The value of the relative humidity X corresponding to can be obtained from the table. As described above, the second reference value B includes the first reference value A stored in the storage unit 4, the ambient temperature value measured by the temperature sensor 2, and the ambient temperature dependency of the relative humidity-capacitance value characteristic. What is necessary is just to calculate using.
In the present embodiment, when it is determined that the capacitance value has shifted, the first reference value A is updated, so that the relative humidity X can be prevented from shifting due to the capacitance value shift.

[Second Embodiment]
Next, in the second embodiment of the present invention, another example of the element unit 1 in the first embodiment will be described. 8A is a plan view of the element portion 1 of the present embodiment, FIG. 8B is a cross-sectional view taken along the line II of FIG. 8A, and FIGS. 3A and 3B. The same code | symbol is attached | subjected to the structure similar to. In the element portion 1 of this embodiment, a plurality of openings 110 (condensation detection structure) are provided in the moisture sensitive film 102 and the upper electrode 103 so that the lower electrode 101 is exposed over a wide range.

  As shown in FIGS. 9A and 9B, when the water droplet 109 generated by condensation adheres to the element portion 1 and the upper electrode 103 and the lower electrode 101 are electrically connected via the water droplet 109, the upper electrode The charging time of the capacitor composed of 103, the moisture sensitive film 102, and the lower electrode 101 is extended. The change in the relative humidity-capacitance value characteristic when the charging time of the capacitor is extended is as described in the first embodiment.

9A shows an example in which condensation occurs on the entire surface of the element portion 1, and FIG. 9B shows an example in which condensation occurs on a part of the element portion 1. In the structure of the element unit 1 according to the first embodiment, it is possible to detect the occurrence of condensation only when water droplets adhere to the notch portion 108, and water droplets adhere to other portions of the element unit 1. In this case, the occurrence of condensation cannot be detected. On the other hand, in the present embodiment, it is possible to detect the occurrence of condensation in a wide area of the element unit 1.
The other configuration of the capacitive humidity sensor is as described in the first embodiment.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. 10A is a plan view of the element portion 1 of the present embodiment, FIG. 10B is a cross-sectional view taken along the line II of FIG. 10A, and FIG. 10C is I of FIG. FIG. 4 is a cross-sectional view taken along the line “-I”, and the same reference numerals are given to the same components as those in FIGS. 3A and 3B. This embodiment shows another example of the element unit 1 of the first embodiment, and has a dew condensation detection structure different from the first and second embodiments.

  Specifically, the dew condensation detection structure is composed of protrusions 111 and 112 arranged to face each other with a gap 113 therebetween. These protrusions 111 and 112 are arranged on the substrate 100 so as to protrude from the lower electrode 101 and the upper electrode 103 with the moisture sensitive film 102 sandwiched therebetween to a region where the moisture sensitive film 102 does not exist.

As shown in FIG. 11, when the water droplet 109 generated by condensation adheres to the element portion 1 and the projections 111 and 112 are conducted through the water droplet 109, the upper electrode 103 and the lower electrode 101 are conducted. The width of the gap 113 in the horizontal direction (FIG. 10A, left-right direction in FIG. 11) may be set so that the protrusions 111 and 112 are electrically connected when condensation occurs.
The other configuration of the capacitive humidity sensor is as described in the first embodiment.

  The structure of the element portion 1 may be as shown in FIGS. 12A, 12B, and 12C. 12A is a plan view showing another structure of the element portion 1 of this embodiment, FIG. 12B is a cross-sectional view taken along the line II of FIG. 12A, and FIG. 12C is FIG. It is I'-I 'sectional view taken on the line of (A). In this example, the pattern of the moisture sensitive film 102 is different from the example shown in FIGS. 10 (A) to 10 (C).

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. 13A is a plan view of the element portion 1 of the present embodiment, FIG. 13B is a cross-sectional view taken along the line II of FIG. 13A, and FIGS. 3A and 3B. The same code | symbol is attached | subjected to the structure similar to. This embodiment shows another example of the element unit 1 of the first embodiment, and has the same dew condensation detection structure as that of the third embodiment. However, the protrusions 111 and 112 constituting the dew condensation detection structure of the present embodiment are not electrode bodies in a state where the moisture sensitive film 102 is sandwiched, but portions where the moisture sensitive film 102 does not exist (electrodes 101 and 103 are electrode pins). 104 and 105 are formed on the substrate 100 so as to protrude from the portion of the terminal to be joined.

  As shown in FIG. 14, when the water droplet 109 generated by condensation adheres to the element portion 1 and the projections 111 and 112 are conducted through the water droplet 109, the upper electrode 103 and the upper electrode 103 are connected to each other as in the third embodiment. The lower electrode 101 is electrically connected.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. When the normal measurement cycle is long (for example, several minutes) or in an installation environment where the ambient humidity is likely to change rapidly, it is expected that the inflection point after the disappearance of the water droplet cannot be recorded. In such a case, only during the period when the condensation state is determined, the measurement cycle is temporarily changed sufficiently short (for example, 1 second or less) so that the capacity value of the inflection point immediately after the disappearance of the water droplet can be measured. Good.

FIG. 15 is a block diagram showing the configuration of the capacitive humidity sensor according to this embodiment, and FIG. 16 is a flowchart for explaining the operation of the capacitive humidity sensor of this embodiment.
The capacitive humidity sensor of the present embodiment is obtained by adding a measurement cycle changing unit 11 to the configuration of the first embodiment. The configuration of the element unit 1 is as described in the first to fourth embodiments.

  When the dew condensation determination unit 5 determines that the dew condensation state is present (YES in step S2 in FIG. 16), the measurement cycle changing unit 11 changes the measurement cycle to a predetermined cycle shorter than the normal cycle (step S9 in FIG. 16). The measurement cycle changing unit 11 determines that the dew condensation state has been eliminated by the dew condensation determination unit 5 (YES in step S3 in FIG. 16), and the inflection point detection unit 6 detects the capacitance value of the inflection point. The measurement cycle is returned to the normal cycle (step S10 in FIG. 16). Here, the process of step S10 is performed after the process of step S4, but the process of step S10 is performed anywhere after any of steps S4, S5, S6, and S7 (S8). Good.

As described in the first embodiment, the capacitance measuring unit 3 measures the capacitance value C between the upper electrode 103 and the lower electrode 101 every measurement cycle. In order to change the measurement cycle as in the present embodiment, the capacitance value calculation unit 34 of the capacitance measurement unit 3 determines the capacitance value between the upper electrode 103 and the lower electrode 101 in accordance with an instruction from the measurement cycle change unit 11. What is necessary is just to change the period which calculates C. Since the relative humidity deriving unit 10 obtains the relative humidity X every time the capacitance value C is measured by the capacity measuring unit 3, when the measurement cycle of the capacity measuring unit 3 is changed, the cycle of the relative humidity deriving unit 10 is accordingly changed. Will also be changed. Other configurations are the same as those described in the first embodiment.
Thus, in the present embodiment, the capacitance value at the inflection point can be easily detected by shortening the measurement cycle while the element unit 1 is in the dew condensation state.

  In the first to fifth embodiments, the element unit 1 may be subjected to a hydrophobic surface treatment for the purpose of positively removing water droplets from the surface of the element unit 1, or the moisture sensitive film 102. The element portion 1 may be arranged so that the film surface of the substrate is vertical.

  The capacitance value calculation unit 34, the storage unit 4, the dew condensation determination unit 5, the inflection point detection unit 6, the reference value calculation unit 7, the comparison unit 8, and the reference of the capacitance measurement unit 3 described in the first to fifth embodiments. The value updating unit 9, the relative humidity deriving unit 10, and the measurement cycle changing unit 11 can be realized by a computer having a CPU (Central Processing Unit), a storage device, and an interface, and a program for controlling these hardware resources. it can. The CPU executes the processes described in the first to fifth embodiments in accordance with a program stored in the storage device.

  The present invention can be applied to a technique for correcting a shift in capacitance value of a capacitive humidity sensor.

  DESCRIPTION OF SYMBOLS 1 ... Element part, 2 ... Temperature sensor, 3 ... Capacity | capacitance measurement part, 4 ... Memory | storage part, 5 ... Condensation determination part, 6 ... Inflection point detection part, 7 ... Reference value calculation part, 8 ... Comparison part, 9 ... Reference | standard Value updating unit, 10 ... Relative humidity deriving unit, 11 ... Measurement cycle changing unit, 30 ... Power source, 31 ... Resistance, 32 ... Switch, 33 ... Voltage detection unit, 34 ... Capacitance value calculating unit, 100 ... Substrate, 101 ... Lower part Electrode, 102 ... moisture sensitive film, 103 ... upper electrode, 104, 105 ... electrode pin, 106, 107 ... conductive paste, 108 ... notch, 110 ... opening, 111, 112 ... projection, 113 ... gap.

Claims (8)

An element part having a structure in which a moisture sensitive film is sandwiched between an upper electrode and a lower electrode;
Capacitance measuring means for measuring a capacitance value between the upper electrode and the lower electrode;
Condensation determination means for determining whether the element unit is in a dew condensation state based on the capacitance value measured by the capacity measurement means;
The capacitance value measured by the capacitance measuring unit immediately after it is determined that the element unit is in a dew condensation state and the dew condensation state is eliminated is set as a capacitance value at an inflection point on the relative humidity-capacitance value characteristic. Inflection point detection means;
Storage means for storing a first reference value which is a capacity value corresponding to a relative humidity of 100% RH when the ambient temperature is a reference temperature;
Reference value calculating means for calculating a second reference value that is a capacity value corresponding to a relative humidity of 100% RH at the current ambient temperature from the first reference value and the current ambient temperature value;
A comparison means for determining whether the capacitance value of the inflection point is different from the second reference value;
When it is determined that the capacity value of the inflection point is different from the second reference value, the latest value of the first reference value is determined from the capacity value of the inflection point and the current ambient temperature value. A reference value updating unit that calculates and updates a value stored in the storage unit,
The capacitive humidity sensor characterized in that the element section has a dew condensation detection structure for causing the inflection point in the relative humidity-capacitance value characteristic. The capacitive humidity sensor according to claim 1, wherein
The storage means stores in advance a capacitance value at the time of condensation,
The dew condensation determining means determines whether or not the element portion is in a dew condensation state by comparing the capacitance value measured by the capacitance measuring means and the capacitance value at the time of dew condensation. . The capacitive humidity sensor according to claim 1 or 2,
The dew condensation detection structure includes a notch portion from which a part of the moisture sensitive film covering the lower electrode is removed so that a part of the lower electrode is exposed on the surface of the element portion. Capacitive humidity sensor. The capacitive humidity sensor according to claim 1 or 2,
The dew condensation detection structure includes a plurality of openings provided in the moisture-sensitive film and the upper electrode so that a part of the lower electrode is exposed on the surface of the element portion. Humidity sensor. The capacitive humidity sensor according to claim 1 or 2,
The dew condensation detection structure is
A first protrusion formed to protrude from the upper electrode;
A capacitive humidity sensor comprising: a second protrusion formed so as to protrude from the lower electrode, and arranged to face the first protrusion with a gap therebetween. The capacitive humidity sensor according to any one of claims 1 to 5,
Further, when the condensation determination unit determines that the condensation state is present, the measurement cycle of the capacity measurement unit is changed to a predetermined cycle shorter than a normal cycle, and the condensation determination unit determines that the condensation state has been eliminated, A capacitive humidity sensor comprising: a measurement cycle changing unit that returns the measurement cycle to a normal cycle after the inflection point detection unit detects a capacitance value of the inflection point. The capacitive humidity sensor according to any one of claims 1 to 6,
The capacitive humidity sensor further comprises relative humidity deriving means for obtaining relative humidity based on the capacitance value measured by the capacitance measuring means, the first reference value, and the current ambient temperature value. The capacitive humidity sensor according to any one of claims 1 to 7,
The capacitive humidity sensor further comprises a temperature sensor for measuring the ambient temperature.