JP2567229B2 - Electronic dew point or frost point measuring device - Google Patents

Description

FIELD OF THE INVENTION The present invention relates generally to electronic dew point or frost point measuring devices,
Particularly, for example, a humidity detecting element that outputs an electric signal according to a humidity change in the atmosphere and a temperature detecting element that outputs an electric signal according to a temperature change in the atmosphere are provided, and air in a greenhouse in greenhouse cultivation of fruits and vegetables. The present invention relates to an electronic dew point or frost point measuring device which is preferably applied when adjusting, defrosting an automobile, or defrosting an electric refrigerator.

Technical background of the invention and its problems As is well known, in this type of electronic dew point measuring device, the electric resistance value of the humidity sensitive element is changed depending on, for example, a change in humidity in the atmosphere, and an electric output is obtained. Use the obtained one, and use the one that can obtain the electric output by changing the electric resistance value of the element according to the temperature change of the atmosphere as well as the temperature sensitive element. After the analog voltage signal output from each of these elements according to the variability is amplified by an amplifier, it is converted into a digital signal by an analog / digital converter (hereinafter referred to as "A / D converter"). A digital electronic circuit control device such as a processor (hereinafter simply referred to as a "microcomputer") measures the humidity value and the temperature value detected by the both elements based on the digital signal. It is designed to calculate the dew point temperature in space.

By the way, as is clear from the above description, in the conventional electronic dew point measuring device, in order to calculate the dew point temperature value in the measurement space in which the microcomputer is based on the analog voltage signals output from both the elements described above, It is necessary to connect an amplifier for amplifying an analog signal output from each of the elements and an A / D converter for converting the analog signal output from the amplifier to a digital signal between the element and the micro computer. Therefore, the entire circuit including the amplifier such as the micro computer and the A / D converter cannot be integrated into one chip LSI. Therefore, it is necessary to reduce the size and power consumption. There was a limit, and it was difficult to achieve cost reduction.

Therefore, in view of the above-mentioned facts, as a result of the inventors of the present invention, as a result of repeated research, the relatively high-priced A / D converter is not used in the electronic dew point measuring device as described above, and the function of the A / D converter is It has been found that the number of components of the circuit can be reduced by complementing the technical means of (1) and the entire circuit can be integrated into one chip LSI. At the same time, the present inventors can also implement the above-mentioned one-chip LSI for an electronic frost point measuring device that can calculate the dew point temperature value described above and also the dew point temperature value in the measurement target space. I found that.

 The present invention is based on such a new finding.

Therefore, the present invention was devised from the above-mentioned background, and its purpose is to eliminate the relatively expensive A / D converter to reduce the number of circuit components. It is possible to reduce the size, power consumption, and cost of a single-chip LSI, and eliminate the effects of variations in the circuit component constants and temperature characteristics.
An object is to provide a highly accurate electronic dew point or frost point measuring device.

Means for Solving the Problems The above object is achieved by the electronic dew point or frost point measuring device according to the present invention. In summary, the present invention provides a pulse signal generator, a resistance type humidity detecting element connected to a feedback circuit of the pulse signal generator, a reference resistance element connected in parallel to the humidity detecting element, A resistance type temperature detection element connected in parallel to the humidity detection element and the reference resistance element, a first switching element for opening / closing the humidity detection element side, and an opening / closing state for the reference resistance element side. A second switching element, a third switching element that opens / closes the temperature detecting element side, and a pulse signal generator, the humidity detecting element, the reference resistance element, and the temperature detecting element, respectively. In order to form a CR time constant circuit, a capacitive element connected to the input side of the pulse signal generator is provided, and the first pulse signal is provided when only the first switching element is closed. The second
Of the oscillating means for outputting a second pulse signal when only the switching element of the above is closed and a third pulse signal when only the third switching element of the above is closed, and a first pulse from the oscillating means. The ratio between the pulse signal and the second pulse signal and the ratio between the third pulse signal and the second pulse signal are respectively calculated, and the relative humidity value and the temperature value are obtained based on the calculation result, and then these values are calculated. An electronic dew point or frost point measuring device, comprising: an arithmetic processing unit that calculates a dew point or a frost point from the electronic dew point or the frost point.

Examples Hereinafter, examples according to the present invention will be described with reference to the drawings.

FIG. 1 shows an electronic dew point measuring device according to a first embodiment of the present invention. The outline of the electronic dew point measuring device according to the first embodiment of the present invention is, as is apparent with reference to FIG. 1, an oscillating means, that is, a square wave pulse oscillator 1 and an output signal of the square wave pulse oscillator 1. It is composed of a digital arithmetic processing means, that is, a microcomputer 9. The above-mentioned square wave pulse oscillator 1 includes a square wave pulse signal generator, that is, an inverter element 7 that outputs a square wave pulse signal that is a logic level signal, a humidity detecting element RH3 connected to a feedback circuit of the inverter element 7, A reference resistance element RO11 connected in parallel to the humidity detection element RH3 in the feedback circuit of the inverter element 7, and the humidity detection element 3 and the reference resistance element RO11 in the feedback circuit of the inverter element 7.
Temperature sensing element RT13 connected in parallel to 11
And a first switching element or SW10 that opens / closes the humidity detecting element RH3 side, and opens / closes the reference resistance element RO11 side.
A second switching element, that is, SW20, that closes, and a third switching element, that is, SW20 that opens / closes the temperature sensing element RT13 side.
It is composed of SW30 and a capacitive element (hereinafter referred to as "capacitor") 5 connected to the input side of the inverter element 7.

The humidity detection element RH3, a resistance type humidity detection element whose electric resistance value changes according to the humidity change in the atmosphere, for example, using a ceramic sintered body or a polymer, the humidity-electricity As shown in Fig. 2, the resistance value characteristic shows that the change in electric resistance value is 30% to 95% in humidity.
It is on the order of 170KΩ to 300KΩ. In the inverter element 7, the electric resistance value of the humidity detecting element RH3 changes in accordance with a change in humidity in the atmosphere, whereby the humidity detecting element RH3 is changed.
When the oscillation frequency in the CR oscillation circuit formed between the electric resistance value of RH3 and the capacitor 5 changes, a square wave pulse signal having a frequency corresponding to the oscillation frequency is output. In the present embodiment, the inverter element 7 is a C-MOS dummy inverter. By using the C-MOS dummy inverter for the inverter element 7 in this way, the cost and power consumption are reduced. As a result, stable square wave pulse signals are obtained even for frequencies on the order of 100 KHZ, for example.

As will be described in detail later, the reference resistance element RO11 is connected in order to improve the accuracy of humidity detection by the humidity detection element RH3 and the accuracy of temperature detection by the temperature detection element RT13. In the temperature detecting element RT13,
A resistance type temperature sensing element such as a thermistor whose electric resistance value changes according to the temperature change of the atmosphere is used. Said
Each of SW10, SW20, and SW30 uses a 3-state buffer element that opens / closes in response to a drive command signal output from the microcomputer 9. The capacitor 5 described above forms a CR time constant circuit, that is, a CR oscillation circuit, among the electric resistance value of the humidity detecting element RH3, the electric resistance value of the reference resistance element RO11, and the electric resistance value of the temperature detecting element RT13. It has become.

In the circuit configuration as described above, the electric resistance value R of the humidity detecting element RH3 is controlled by the microcomputer 9
The oscillation frequency fH of the square wave pulse signal output from the square wave pulse oscillator 1 when only the SW10 corresponding to the ratio RO of the H to the resistance value RO of the reference resistance element RO11: RO / RH is closed and The ratio rf≡fH / fO of the square wave pulse signal output from the square wave pulse oscillator 1 when only the SW20 is closed to the oscillation frequency fO is calculated, and the electric resistance value of the temperature detecting element RT13 is calculated. Ratio of RT to resistance value RO of the reference resistance element RO11: Oscillation frequency fT of the square wave pulse signal output from the square wave pulse oscillator 1 when only the SW30 corresponding to RO / RT is closed and The ratio r′f≡fT / fO of the square wave pulse signal output from the square wave pulse oscillator 1 when only the SW20 is closed to the oscillation frequency fO is also calculated, and rf≡fH / fO = RO From the relational expression of / RH, R = RH = RO / rf
By obtaining the value of H, the humidity value in the atmosphere is obtained from the value of RH and the data shown in FIG. 2, and, on the other hand,
An atmospheric temperature value is obtained from the value of r′f≡fT / fO and the temperature-fT / fO characteristic value data of the temperature detecting element RT13 as shown in FIG. 3 stored in the memory of the microcomputer 9. It was decided. The circuit configuration of the square wave pulse oscillator 1 of the electronic dew point measuring device according to the first embodiment of the present invention is set as described above for the reason described below. That is, the oscillation frequency f of the oscillator 1 depends on the capacitance C of the capacitor 5 and the Hi of the inverter element 7.
It has been found that the level threshold voltage VTH, the LO level threshold voltage VTL of the element 7, the output voltage VO of the oscillator 1, the variation in the value of the constant k, the temperature characteristics, and the like have some influence. Therefore, as described above, the inventors of the present invention connect the reference resistance element RO11 to the humidity detection element 3 in parallel, and when the SW1 and SW2 are respectively provided and one is closed, the other is opened. Oscillation frequency when only SW1 is closed Can be obtained by ), Oscillation frequency when only SW2 is closed (The formula will be described later)}. ) Is counted by the micro computer 9, and then fH
By eliminating the VTH, VTL, VO, k, and C by taking the ratio of f0 and fO and determining the value of the oscillation frequency f only by the value of RO / RH, a more accurate humidity measurement value can be obtained. I was able to get the data. In the reference resistance element RO11 described above, the resistance value variation due to the influence of the temperature change or the like is VTH, VTL, VO,
Since it is almost negligible compared to the characteristic value fluctuations of C, k, etc., the values of VTH, VTL, VO, C, k, etc. are determined by obtaining the value of rf, that is, fH / fO. At the very least, the value of rf is determined only by the change in the electric resistance value RH of the humidity detecting element 3, so that more accurate humidity measurement can be performed.

On the other hand, at the time of temperature detection, the oscillation frequency f output from the square-wave pulse oscillator 1 depends on variations in the values of C, k, VTH, VTL, VO, temperature characteristics, etc., as in the above-described humidity detection. It was found that the influence of VTH, VTL, VO, k, and C can be eliminated by using the relationship between fT / fO and the temperature value as described above. It's done.

The above-described microcomputer 9 has a CPU that performs arithmetic and logical operations, a counter that counts the square wave pulse signal output from the square wave pulse oscillator 1, a memory that stores a control program, and stores necessary data. Equipped with output ports and so on. Examples of the data stored in the memory of the microcomputer 9 include the following items.

(A) Humidity detecting element RH3 as shown in FIG.
Humidity-electric resistance characteristic data of (b) temperature compensation value data of the humidity detecting element RH3 (c) oscillation frequency f of the square wave pulse signal output from the square wave pulse oscillator 1 shown in FIG. Formula showing the relationship with the electric resistance R of the humidity sensing element RH3 However, VO: output voltage of the square wave pulse oscillator 1 VTH: Hi level threshold voltage of the inverter element 7 (that is, C-MOS shift inverter) VTL: the inverter element 7 (that is, C-MOS shift inverter) LO level threshold voltage k: constant (Note that the relation between the electric resistance value RT of the temperature detecting element RT13 and the oscillation frequency f of the square wave pulse signal output from the square wave pulse oscillator 1 is expressed by the above equation. (C ') Oscillation frequency data with a certain range output from the square wave pulse oscillator 1 (d) Temperature-fT / fO characteristics of temperature sensing element RT13 as shown in FIG. Value data (e) Relative humidity value in the space to be measured detected by the humidity detecting element RH3 of the square wave pulse oscillator 1 shown in FIG. 1 and temperature sensing element of the square wave pulse oscillator 1 Formula for obtaining the dew point temperature in the measurement target space from the temperature value in the measurement target space detected by the child RT13 TD = −5278 / ln {H × 1.162 × 10 ⁹ exp (−5278 / T ′) / 1.162 × 10 ¹¹ ) However, TD: dew point temperature value H: relative humidity value T ': absolute temperature value (temperature value +273.15) (f) Temperature in the measurement target space detected by the temperature detection element RT13 Approximate expression to obtain saturated vapor compression at the temperature value from the value es1.162 × 10 ⁹ exp (−5278 / T ′) ……, where es: Saturated vapor pressure T ′: Absolute temperature value (temperature value +273.15) (F ') Temperature and measured value of saturated water vapor pressure es at the temperature value (see attached table) (G) Formula for obtaining the water vapor pressure value in the measurement target space from the relative humidity value in the measurement target space detected by the humidity detection element RH3 and the saturated water vapor pressure value obtained by the above formula e = es × H / 100 ...... However, e: Water vapor pressure value (h) An equation for obtaining the dew point temperature value at which the water vapor pressure value in the measurement target space obtained by the above equation becomes a saturated water vapor pressure value TD = −5278 / ln (e / 1.162 × 10 ⁹ ) ... (However, in the above equation, es is replaced by e and T is replaced by
It can also be obtained by substituting TD for each, and the formula can also be obtained from the formula and the formula. In this embodiment, the CPU of the microcomputer 9 described above is a 4-bit or 8-bit standard CPU.

In the configuration described above, the CPU of the microcomputer 9 counts the frequency f of the square wave pulse signal output from the square wave pulse oscillator 1 described above, and the oscillation frequency f of the counted square wave pulse signal and the memory. The humidity detection element RH3 from the formula stored in
Electric resistance value RH and / or the electric resistance value RT of the temperature detection element RT13 is calculated, and the calculated electric resistance value RH of the humidity detection element RH3 and the above-mentioned electric resistance value RH stored in the memory shown in FIG. The relative humidity value H in the measurement target space is obtained from the humidity-electric resistance value characteristic data of the humidity detection element RH3, and the calculated electric resistance value RT of the temperature detection element RT13 and the temperature detection shown in FIG. Element RT13 temperature −fT / fO
The temperature value T in the measurement target space is calculated from the characteristic value data, and the dew point temperature value TD in the measurement target space is calculated from the calculated relative humidity value and temperature value by the formula stored in the memory. , The saturated water vapor pressure value es is obtained from the temperature value T and the equation stored in the memory, and the measurement is performed by the equation stored in the memory from the saturated water vapor pressure value es and the relative humidity value H. The water vapor pressure value e in the target space is obtained, and thereafter, the dew point temperature value TD in the measurement target space is obtained from the water vapor pressure value e and the formula stored in the memory.

The content described above relates to the first embodiment of the present invention, and does not mean that the present invention is limited to the above content.

FIG. 4 shows an electronic dew point measuring device according to a second embodiment of the present invention.

The electronic dew point measuring apparatus according to the second embodiment of the present invention and the first embodiment include the provision of warning means 15 such as an alarm as shown in FIG. 4 of the present embodiment. , The memory contents stored in the memory of the microcomputer 9 and the arithmetic processing operation of the CPU of the microcomputer 9 are different. That is, in the present embodiment, in the memory described above, instead of the formula stored in the memory, an approximation formula of the formula is expressed as es = AT ² + B (where A and B are the temperature detection values). When the temperature range detected by the element RT13 is divided into, for example, 5 ° C intervals as one section, the temperatures at both ends of each section are (T ₁ , T ₂ ), and the corresponding saturated water vapor pressure is (e ₁ , e ₂ ). And when You can ask for each. ) Dew point temperature obtained by inverse conversion of the above equation
Formula for TD Etc. are stored, the temperature value T corresponding to the temperature detecting element given from the temperature detecting element RT13 is read at 5 ° C. intervals with the upper limit value and the lower limit value of the section, and the saturated vapor pressure value es is calculated by the above formula. Along with the calculation, the humidity sensing element RH3
From the relative humidity value H corresponding to the humidity detection signal given by and the saturated water vapor pressure value es, the water vapor pressure value e is obtained by the above equation, and the dew point temperature value TD is calculated by the above equation. Of course, it does not matter if the method of directly determining the es by directly using the memory contents of (f) and (f ') is adopted. Further, in the present embodiment, the dew point temperature at which the temperature value T of the measurement target space obtained as described above is changed in the memory and the water vapor pressure e at the temperature value T becomes the saturated water vapor pressure value es. The allowable temperature value ΔT that can be allowed to approach the value TD is stored, and when the relationship of TTD + ΔT is established between the temperature value T and the dew point temperature value TD, the CPU can A program for outputting a drive command signal to the alarm means 15 is stored. The allowable temperature value Δ
Since the accuracy of T and TD is affected by the accuracy of the temperature detecting element RT13 and the circuit of the present apparatus, T is set in consideration of this point. Further, ΔT does not have to be one value, and may be a plurality of values. CPU mentioned above
The alarm means 15 when the temperature value T obtained on the basis of the temperature detection signal from the temperature detection element RT13 and the dew point temperature value TD are constantly compared with each other to recognize that TTD + ΔT is reached. A drive command signal is output to. When there are a plurality of ΔT values stored in the memory, the CPU compares the result of the comparison operation with the plurality of ΔT values set and issues an alarm in a stepwise manner. It is also possible to output a drive command signal to the alarm means 15.

As a modification of the present embodiment, for example, the warning means 15 is provided over a temperature value T and a relative humidity value H corresponding to the temperature value T.
Two sections are set to judge whether or not to drive, and the temperature value ΔT ₁ and the relative humidity values H ₁ and ΔT ₂ corresponding to each section are set.
And the relative humidity value H ₂ corresponding to the
TD + ΔT ₁ and / or HH _{1 When} the relationship of TTD + ΔT ₂ and / or HH ₂ (where ΔT ₁ > ΔT ₂ and H ₁ <H ₂ ) is established in the second stage, It is also possible to drive the alarm means 15 respectively. Furthermore, after collecting various test data, the temporal changes of T, TD, and H are obtained, and the data relating to the temporal changes of these values are stored in the memory, and based on the data, If the alarm means 15 is driven, it is possible to predict the time when the temperature value T of the measurement target space reaches the dew point temperature value TD.

As a third embodiment according to the present invention in addition to the first and second embodiments according to the present invention described above, a relative humidity value H, a temperature value T, and a dew point temperature value TD are stored in the memory of the microcomputer 9. First data indicating the relationship or dew point temperature value TD
One of the second data indicating the relationship between the temperature value T of the atmosphere and the saturated water vapor pressure value es of water when obtaining the above is stored in advance, and the CPU outputs the square wave pulse wave from the square wave pulse oscillator 1 respectively. The relative humidity value H and the temperature value T in the measurement target space obtained based on the wave pulse signal and the first data are used to obtain the dew point temperature value TD in the measurement target space, or the second data By calculating the water vapor pressure value e in the measurement object space from the saturated water vapor pressure value es corresponding to the temperature value T in the inside and the relative humidity value H by the formula stored in the memory, The dew point temperature value TD may be obtained from the calculated value e and the second data.

FIG. 5 shows an electronic dew point measuring device according to a fourth embodiment of the present invention.

The outline of the electronic dew point measuring device according to the fourth embodiment of the present invention is, as will be apparent with reference to FIG. 5, the square wave pulse oscillator 1 having the circuit configuration shown in FIG. The first protection resistance element, that is, the protection resistance element R1 is connected in parallel to the humidity detection element RH3 connected to the feedback circuit 7 and the humidity detection element RH3 and the protection resistance element R1 are connected in parallel. A second protective resistance element, that is, a series body of a fixed resistance element R2 and a variable resistance element VR2 is connected in series to the formed combined resistance, and the humidity detection element RH3 is connected.
The third protective resistance element, that is, the variable resistance element VR3 is connected in series to the reference resistance element RO11 which is connected in parallel with the reference resistance element RO11, and is connected in parallel to the humidity detection element RH3 and the reference resistance element RO11. Fourth for temperature sensing element RT13
The protective resistance element, namely, the protective resistance element R4 is connected in series. The reason why the square wave pulse oscillator 1 is configured as described above is that the variable ranges of the electric resistance values of the humidity detecting element RH3 and the temperature detecting element RT13 which are variable according to the humidity change in the atmosphere and the temperature change of the atmosphere. By regulating the value so that it does not exceed a predetermined value or below a predetermined value, the frequency of the signal output from the square wave pulse oscillator 1 does not deviate from the setting range of the oscillation frequency data as described above. In addition, the humidity detection element RH3 and the temperature detection element RT13 are connected to the reference resistance element RO1.
For example, when the variable resistor VR3 is adjusted to compensate for the variable resistance value of the temperature detection element RT13 due to the shared use of 1, the humidity detection element RH3 is affected by the adjustment and the humidity measurement accuracy is improved. The variable resistance element VR2 is adjusted according to the adjustment of the variable resistance element VR3 so as not to decrease. In the electronic dew point measuring device according to the present invention, the humidity detecting element RH3, the temperature detecting element RT13, etc. are connected to the feedback circuit side of the inverter element 7, and the capacitor 5 is connected to the input side of the inverter element 7. However, the humidity detecting element RH3, the temperature detecting element RT13, etc. are connected to the input side of the inverter element 7, and the capacitor 5
May be connected to the feedback circuit side of the inverter element 7.

Next, an electronic dew point or frost point measuring device according to a fifth embodiment of the present invention will be described. The structure of the square wave pulse oscillator of the electronic dew point or frost point measuring device according to the fifth embodiment of the present invention is the same as the structure of the square wave pulse oscillator 1 according to the first embodiment shown in FIG. Also, for the microcomputer 9 as well, the CPU of 4 bits or 8 bits is used as in the first to fourth embodiments, so that the description thereof will be omitted and the square wave pulse oscillator 1 will be described below. The arithmetic processing operation of the microcomputer 9 based on the output square wave pulse signal will be described. In this embodiment, data indicating the relationship between the temperature value T of the atmosphere and the saturated water vapor pressure value es of water, that is, the temperature value T in the measurement target space is 0 in the memory of the microcomputer 9.
First data showing the relationship between the temperature value T applied when the temperature exceeds T and the saturated water vapor pressure value es of water, and when the temperature value T in the measurement target space is within the range of 0 ° C. or less. Second data indicating the relationship between the applied temperature value T and the saturated water vapor pressure value es of supercooled water is stored in advance. On the other hand, for the CPU of the microcomputer 9, the SW corresponding to the ratio of the electric resistance value RH of the humidity detecting element RH3 and the resistance value RO of the reference resistance element RO11: RO / RH
The oscillation frequency fH of the square wave pulse signal output from the square wave pulse oscillator 1 when only 10 is closed and the SW
Ratio rf of the square wave pulse signal output from the square wave pulse oscillator 1 when only 20 is closed to the oscillation frequency fO
≡fH / fO is calculated and the temperature sensing element RT13
Square wave pulse signal output from the square wave pulse oscillator 1 when only the SW30 is closed, which corresponds to the ratio of the electric resistance value RT of the resistance value RO of the reference resistance element RO11 to the resistance value RO of the reference resistance element RO11: RO / RT. Of the square wave pulse signal output from the square wave pulse oscillator 1 when only the SW20 is closed, and the ratio r′f≡fT / fO is calculated as rf≡ By calculating the value of RH at RH = RO / rf from the relational expression of fH / fO = RO / RH, the humidity value in the atmosphere can be calculated from the value of RH and the data shown in FIG. On the other hand, the value of r′f≡fT / fO and the microcomputer 9
The temperature value of the atmosphere is obtained from the temperature-fT / fO characteristic value data of the temperature detecting element RT13 as shown in FIG.

Further, according to the present embodiment, the CPU obtains the saturated water vapor pressure value es at the temperature value T from the temperature value T in the measurement target space by the above-mentioned equation, and the temperature value T is 0.
When it is recognized that the temperature is above the temperature range, the relative humidity value H and the saturated water vapor pressure value es in the measurement target space are
From the above, the water vapor pressure value e is calculated by the above equation, and the dew point temperature value TD at which the calculated value e becomes the saturated water vapor pressure value es is obtained by either the above equation or the first data. . On the other hand, when the CPU recognizes that the temperature value T is in the temperature range of 0 ° C. or less, the saturated water vapor pressure value es obtained by the equation is the saturated water vapor pressure value es in the second data.
Higher or equal or lower, and when it is determined to be higher or equal, the measured temperature value T is determined to be the frost point temperature value TD, and when it is determined to be lower, the obtained saturated water vapor pressure is determined. The temperature value T corresponding to the saturated water vapor pressure value es in the second data that matches the value es is determined as the frost point temperature value TD.

Next, an electronic dew point or frost point measuring device according to a sixth embodiment of the present invention will be described.

The electronic dew point or frost point measuring device according to the sixth embodiment of the present invention and the fifth embodiment are provided with an alarm means 15 such as an alarm as shown in FIG. 4 of the present embodiment. Starting from the above, the contents stored in the memory of the microcomputer 9 and the arithmetic processing operation of the CPU of the microcomputer 9 are different. That is, in the present embodiment, instead of the formula stored in the memory and the method of calculating es from the data of (f) or (f '), the formula is an approximate formula of the formula. es = AT ² + B (where A and B are the temperatures at both ends of each section when the temperature region detected by the temperature detecting element RT13 is divided into, for example, 5 ° C. intervals as one section, (T ₁ , T ₂ ), and the corresponding saturated water vapor pressure is (e ₁ , e ₂ ), You can ask for each. ) Dew point temperature obtained by inverse conversion of the above equation
Formula for calculating TD or frost point temperature TD Etc. are stored, the temperature value T corresponding to the temperature detection signal given from the temperature detection element RT13 is read at an interval of 5 ° C. with the upper limit value and the lower limit value of the section, and the saturated vapor pressure value es is calculated by the above formula. Along with the calculation, the humidity sensing element RH3
From the relative humidity value H corresponding to the humidity detection signal given by the above and the saturated water vapor pressure value es, the water vapor pressure value e is obtained by the above equation, and the dew point temperature value TD or the frost point temperature value TD is calculated by the above equation. I decided to do it. Of course, it does not matter if the method of directly determining the es by directly using the memory contents of (f) and (f ') is adopted. Further, in the present embodiment, the dew point temperature at which the temperature value T of the measurement target space obtained as described above is changed in the memory and the water vapor pressure e at the temperature value T becomes the saturated water vapor pressure value es. Value TD or allowable temperature value ΔT that can be allowed to approach the frost point temperature value TD is stored, and between the temperature value T and the dew point temperature value TD or the frost point temperature value TD. It is assumed that a program is stored such that the CPU outputs a drive command signal to the alarm means 15 when the relationship of TTD + ΔT is established. The allowable temperature value ΔT is set in consideration of this point because the accuracy of the T and TD is affected by the accuracy of the temperature detecting element RT13 and the circuit of the present apparatus. Further, ΔT does not have to be one value, and may be a plurality of values. The above-mentioned CPU constantly compares the temperature value T obtained based on the temperature detection signal from the temperature detection element RT13 with the dew point temperature value TD or the frost point temperature value TD to obtain TTD + ΔT. When this is recognized, a drive command signal is output to the alarm means 15. When there are a plurality of ΔT values stored in the memory, the CPU compares the result of the comparison operation with the plurality of ΔT values set and issues an alarm in a stepwise manner. It is also possible to output a drive command signal to the alarm means 15, as a modified example of the present embodiment, for example, the alarm means over a temperature value T and a relative humidity value H corresponding to the temperature value T. 15
Two sections are set to judge whether or not to drive, and the temperature value ΔT ₁ and the relative humidity values H ₁ and ΔT ₂ corresponding to each section are set.
And the relative humidity value H ₂ corresponding to the
TD + ΔT ₁ and / or HH _{1 When} the relationship of TTD + ΔT ₂ and / or HH ₂ (where ΔT ₁ > ΔT ₂ and H ₁ <H ₂ ) is established in the second stage, It is also possible to drive the alarm means 15 respectively. Furthermore, after collecting various test data, the temporal changes of T, TD, and H are obtained, and the data relating to the temporal changes of these values are stored in the memory, and based on the data, If the alarm means 15 is driven, it is possible to predict the time when the temperature value T of the measurement target space reaches the dew point temperature value TD or the frost point temperature value TD.

As a seventh embodiment according to the present invention in addition to the fifth and sixth embodiments according to the present invention, a relative humidity value H, a temperature value T and a dew point temperature value TD are stored in a memory of the microcomputer 9. First data indicating the relationship or dew point temperature value TD
Any one of the second data indicating the relationship between the atmospheric temperature value T and the saturated water vapor pressure value es of water for obtaining the above is stored in advance, and the atmospheric temperature change output from the square wave pulse oscillator 1 is stored. When the temperature value in the measurement target space obtained based on the square wave pulse signal according to the above is in the temperature region exceeding 0 ° C., the CPU causes the square wave pulse oscillator 1 to
Relative humidity value H and temperature value T in the measurement object space obtained based on the square wave pulse signals respectively output from
Or from the first data to obtain the dew point temperature value TD in the measurement target space, or from the saturated vapor pressure value es and the relative humidity value H corresponding to the temperature value T in the second data. The dew point temperature value TD is obtained from the calculated value e and the second data by calculating the water vapor pressure value e in the measurement target space using the formula stored in the memory. There are also things. In addition,
In addition to the above-described first to seventh embodiments, the present invention is illustrated in FIG. 5 and the microcomputer 9 for performing the arithmetic processing operation as described in the fifth to seventh embodiments. An electronic dew point or frost point measuring device according to an eighth embodiment of the present invention, which comprises a square wave pulse oscillator having the above-mentioned configuration, is included. Since the configuration of the pulse oscillator is the same as that shown in FIG. 5, the description thereof will be omitted. The above description has been made on the assumption that the latent heat at the time of evaporation is constant regardless of the temperature change. However, if the latent heat can be changed depending on the temperature, the process of the various arithmetic processing described above is performed. Since there will be some error in the value obtained by the above, in such a case, for example, if an atmospheric pressure measuring means is provided and the above calculated value is corrected by the measured value given from this means, the dew point temperature value is further increased. It is also possible to improve the measurement accuracy of the frost point temperature value.

Effects of the Invention As described above, according to the electronic dew point or frost point measuring device of the present invention, the relatively expensive A / D converter is not necessary, and the number of components of the circuit can be reduced. It is possible to realize a 1-chip LSI, which can further reduce the size, reduce power consumption, and reduce cost, and eliminate the influence of variations in component constants in the circuit and temperature characteristics. , The dew point or frost point can be measured with high accuracy.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an electronic dew point measuring device according to first and third embodiments of the present invention and an electronic dew point and frost point measuring device according to fifth and seventh embodiments of the present invention. FIG. 2 is a humidity-electrical resistance value characteristic diagram of the humidity detecting element used in the electronic dew point or frost point measuring apparatus shown in FIGS. 1, 4, and 5. FIG. 3 is a temperature-fT / fO characteristic diagram of a temperature detecting element used in the electronic dew point or frost point measuring apparatus shown in FIGS. 1, 4, and 5. FIG. 4 is a circuit configuration diagram of an electronic dew point measuring device and an electronic dew point / frost point measuring device according to the second and sixth embodiments of the present invention. FIG. 5 is a circuit configuration diagram of an electronic dew point measuring device and an electronic dew point / frost point measuring device according to the fourth and eighth embodiments of the present invention. 1: Square wave pulse signal oscillator 3: Humidity detection element RH 5: Capacitor C 7: Inverter element 9: Microcomputer 11: Reference resistance element RO 13: Temperature detection element RT SW10: 3-state buffer SW20: 3-state buffer SW30 : 3 state buffer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norihiro Kiuchi 1-12-32 Akasaka, Minato-ku, Tokyo Within Japan Mining Co., Ltd. (56) Reference JP-A-59-146378 (JP, A) JP 55-1507 (JP, A) JP 56-112637 (JP, A) JP 60-1544 (JP, A) JP 58-151546 (JP, A) JP 61-68527 (JP , A)

Claims (4)

(57) [Claims] 1. An inverter element, a resistance type humidity detecting element connected to a feedback circuit of the inverter element, a reference resistance element connected in parallel to the humidity detecting element, the humidity detecting element and the reference. A resistance type temperature detecting element connected in parallel to each of the resistance elements, a first switching element for opening / closing the humidity detecting element side, and a second switching element for opening / closing the reference resistance element side. And a third switching element for opening / closing the temperature detecting element side, and a CR time constant circuit between the inverter element, the humidity detecting element, the reference resistance element and the temperature detecting element. , And a capacitance element connected to the input side of the inverter element, so that when only the first switching element is closed, the first pulse signal and the second Square wave pulse oscillating means for outputting a second pulse signal when only the switching element is closed and a third pulse signal when only the third switching element is closed, and stored data and Based on the calculation formula,
Of the oscillation frequency of the pulse signal and the second pulse signal and the ratio of the oscillation frequency of the third pulse signal and the second pulse signal are respectively calculated, and the relative humidity value and the temperature value are calculated based on the calculation result. And an arithmetic processing means for calculating the dew point or the frost point from these values. 2. In the oscillating means, a first protective resistance element is provided in parallel with the humidity detecting element, and a first resistance element is connected in series with a combined resistance formed by the humidity detecting element and the first protective resistance element. A second protective resistance element formed by serially connecting a fixed resistive element and a variable resistive element, and a third protective resistive element formed of a variable resistive element in series with the reference resistive element as the temperature detecting element. The electronic dew point or frost point measuring device according to claim 1, wherein a fourth protective resistance element is connected in series to each other. 3. The arithmetic processing means recognizes that a temperature value obtained based on a pulse signal from the oscillating means exceeds a preset temperature range and approaches a dew point, or the oscillating means. Claim 1 characterized in that an alarm means is provided for issuing an alarm when recognizing that the relative humidity value obtained based on the pulse signal from the above exceeds a preset humidity range. The electronic dew point or frost point measuring device according to the second item. 4. The dew point or frost point is calculated by dew point or frost point = −5278 / ln {relative humidity value × 1.162 × 10 ⁹ exp (−5278
/ Absolute temperature value) /1.162×10 ¹¹ }, or
Or, saturated water vapor pressure value = 1.162 × 10 ⁹ exp (−5278 / absolute temperature value) is used to obtain the saturated water vapor pressure value, then the saturated water vapor pressure value and the relative humidity value are used to obtain the water vapor pressure value, and the dew point or frost Claim 1 which is carried out using the formula of point = -5278 / ln (water vapor pressure value / 1.162 × 10 ⁹ ).
Item 2. The electronic dew point or frost point measuring device according to item 2 or 3.