JPS5943346A - Humidity detector - Google Patents

Abstract

PURPOSE:To obtain a humidity detector compact and with a low power consumption by employing a C-MOS ring oscillator having a relative humidity detection element serving an charge/discharge capacitance in a CR type oscillator. CONSTITUTION:A humidity detector 17 is made up of a C-MOS ring oscillator 21, frequency division circuit 23, an upcounter 24, a latch circuit 25, a humidity computing circuit 26 and the like. The ring oscillator 21 have a relative humidity detection element 6 comprising a glass-ceramics thick film humidity detection element serving as charge/discharge capacitance in a CR type oscillator. Therefore, the contents to be latched into the latch circuit 25 give a digital value varying according to the relative humidity in the atmosphere. Thus, it is made possible to obtain a digital value according to changes in the relative humidity value without use of an A/C converter thereby producing a humidity detector, compact and with a low power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a relative humidity detection element for detecting relative humidity, and a conversion circuit for converting the detection result by the detection element into digital value data and outputting it. The present invention relates to a humidity detection device.

In recent years, not only electronic circuit technology but also temperature, pressure,
Sensor technology related to humidity, etc. is also developing significantly.
Sensor technology has even been applied to some so-called household electrical appliances.

However, conventional humidity detection devices are generally large in size and consume a lot of power. It was unsuitable to be built into some of the equipment, etc.

In other words, conventional humidity detection devices generally use detection elements to form a bridge circuit, and furthermore, use the same conventional analog-to-digital conversion circuit to convert the detection results into digital values. The reality is that as the size increases, so does the power consumption.

The purpose of the present invention is to provide, for example, a portable size calculator or clock.
A small and low-consumption device that is suitable for being installed in humidity detection devices that are battery-powered and small in size, such as wristwatches, and other portable measurement devices. An object of the present invention is to provide an electric-powered humidity detection device.

Hereinafter, details of the present invention will be explained with reference to the drawings.

Figures 1 to 7 are diagrams showing one embodiment of the present invention.
FIG. 1 is a plan view showing the appearance of a clock-equipped calculator equipped with a humidity detection device according to an embodiment of the present invention. The calculator of this embodiment has a liquid crystal display device 1 as an electro-optical display device, and has a keyboard switch group 2 for calculations and a slide switch Sw for mode selection as external operating members. Further, on the front side of the case 3, a housing section 4 for a humidity detection element is provided.

Next, FIG. 2 is a cross-sectional view showing the internal structure of the humidity detection element accommodating part 4, in which a detection element support plate 5 is fixed to a recess 3a provided in a part of the case 3. Further, a relative humidity detection element 6 is attached on the support plate 5.

That is, the detection element 6 includes a pair of lead electrodes 6a,
6b, which are fixed in electrical connection with the connection electrodes 5a and 5b provided on the support plate 5, respectively.

Note that a portion of the connection electrodes 5a, 5b is configured to reach the lower surface side of the support plate 5 via a through-hole portion. Furthermore, in the opening of the recess 3a of the case 3,
A protection plate 7 with a through hole 7a is attached, and the protection plate 7 protects the relative humidity detection element 6, and the detection element 6 is exposed to water vapor in the external atmosphere through the through hole 7a. The composition is configured such that the following components are introduced.

Furthermore, 8 is a circuit board, 9 is a liquid crystal display device support member, and 10
is a connector made of a coil spring, and the connector 10
serves to electrically connect a predetermined wiring pattern (not shown) on the circuit board 8 and the connection electrodes 5a, 5b.

Next, FIG. 3 is a block diagram showing the outline of the circuit configuration of the calculator with a clock according to this embodiment, in which 11 is a crystal oscillation circuit serving as a time reference, 12 is a frequency dividing circuit, and 13 is a time counter. Further, the aforementioned keyboard switch group 2 is connected to the input control circuit 14, and the time adjustment signal d and calculation execution signal c output from the input control circuit 14 are as follows.
The signals are configured to be input to the time counter 13 and calculation circuit 15, respectively.

Furthermore, 17 is a humidity detecting device including the above-mentioned relative humidity detecting element 6, and 16 is a sampling link timing control for supplying the humidity detecting device 17 based on signals from the frequency dividing circuit 12 and the time counter 13. This is a clock signal forming circuit that forms each clock signal φi for various purposes.

In addition, each output signal from the time counter 13 and the calculation circuit 15 and the humidity calculation output signal h from the humidity detection device 17
is selected by the decoder through selection control by the display control circuit 18.
It is input to the driver circuit 19 and the above-mentioned liquid crystal display device 1
is configured to drive.

On the other hand, the switch terminal a of the slide switch Sw mentioned above,
b and c are connected to the display control circuit 18 to control the display selection state of the liquid crystal display device 1, terminals a and b are connected to the input control circuit 14, and terminal c is connected to the humidity detection device 17. , are connected to each other.

That is, in the calculator of this embodiment, when the slide switch Sw for mode selection is closed between switch terminal a, the liquid crystal display device 1 is controlled to the time display mode, and in this state, the keyboard switch group 2 In response to the operation, the switch input control circuit 14 outputs a time correction signal d, and the contents of the time counter 13 are corrected.

Further, when the switch Sw is closed between terminal b, the liquid crystal display device 1 is controlled to the calculation display mode, and in this state, in response to the operation of the keyboard switch group 2, the switch input control circuit 14 The signal e will be input to the calculation circuit 15.

Furthermore, when the switch Sw is closed between the terminal c and the liquid crystal display device 1, the liquid crystal display device 1 is controlled to the humidity display mode,
In this state, the humidity detection device 16 performs a humidity detection operation and outputs a humidity calculation output signal h.

In the constant voltage circuit G, fluctuations in the voltage of the power supply battery E due to changes in the environment such as temperature or the passage of time can cause the oscillation frequency of the crystal oscillation circuit 11 or the oscillation of the C-MOS ring oscillator 21 (described later) in the humidity detection device 17 to be controlled by the constant voltage circuit G. This is provided to eliminate the influence on the frequency, and in this embodiment, at least the crystal oscillation circuit 11 and the C-MOS ring oscillator 21, which will be described later, are provided.
It is configured to be driven by the output voltage of the constant voltage circuit G.

However, in FIG. 3, to simplify the diagram, the power supply relationship from the constant voltage circuit G is shown by a broken line, and other components other than the humidity detection device 17 including the crystal oscillation circuit 11 and the C-MOS ring oscillator 21 are shown. Although the relationships for supplying power to other elements are not shown in the drawings, it is clear that in practice power may also be supplied to the other elements mentioned above via the constant voltage circuit G.

Next, FIG. 4 shows an example in which a glass-ceramic thick film humidity detection element having a characteristic that the capacitance value changes approximately linearly with an increase in relative humidity is used as the above-mentioned relative humidity detection element 6. FIG. 5 is a circuit diagram showing a specific example of the humidity detecting device 17; FIGS. It is a graph showing humidity/capacity conversion characteristics.

The above glass-ceramic thick film humidity detection element is
As shown in FIG. 5, a pair of electrodes 6c, 6 are provided on the surface.
an insulating substrate 6e made of alumina or the like having
f, and a thickness of 30~ formed on the dielectric layer 6f.
It is composed of 6g of moisture-sensitive dielectric layer of about 50μm,
The pair of electrodes 6c and 6d are formed as so-called comb-shaped opposing electrodes.

The moisture-insensitive dielectric layer 6f is formed by printing and baking a dielectric paste on the alumina substrate 6e, and the moisture-sensitive dielectric layer 6f is formed by printing metal oxide such as alumina particles on the moisture-insensitive dielectric layer 6f. It is formed by screen-printing a multilayer moisture-sensitive dielectric paste containing glass fine particles and the like, and then firing the paste. Since particles of metal oxide such as alumina do not melt during this firing, the moisture-sensitive dielectric layer 6g is made of porous glass-ceramic with the surface of metal oxide particles 6j such as alumina wrapped in a glass-ceramic film 6k. The system has a thick film structure.

Note that the pair of electrodes 6c and 6d are connected to the aforementioned lead electrodes 6a and 6b, respectively. In addition to alumina, metal oxides such as cobalt, indium, palladium, nickel, manganese, tin, copper, and iron can be used as the metal oxides.

As shown in FIG. 6, the glass-ceramic thick film humidity detection element having the above structure has a characteristic that the capacitance Ch increases almost linearly as the relative humidity H increases. There is. FIG. 7 is a time chart of each clock signal φi supplied from the clock signal forming circuit 16 to the humidity detecting device 17.

In this embodiment, the humidity detection device 17 is
C-, where the relative humidity detection element 6 made of a ceramic thick film humidity detection element has a charge/discharge capacity in CR type oscillation.
It is composed of a MOS ring oscillator 21, a frequency dividing circuit 23, an up counter 24, a latch circuit 25, a humidity calculation circuit 26, and the like.

In addition to the relative humidity detection element 6, the C-MOS ring oscillator 21 includes a feedback resistor 27, a current limiting resistor 28, and a C-MOS ring oscillator 21.
It is a CR type oscillator consisting of an S-NAND circuit 29 and C-MOS inverters 30 and 31, and is a ring oscillator with odd stages subjected to capacitor modulation, and the oscillation frequency f of the oscillator 21 is as described above. When the capacitance value of the humidity detection element 6 is Ch and the resistance value of the feedback resistor 27 is R, it is given by the following equation (1).

f=1/(22ChR)...Formula (1), the fourth
Although the illustration of the power supply line supplied to the oscillator 21 is completely omitted in the figure, in order to completely eliminate the influence of the voltage fluctuation of the power supply battery E on the oscillation frequency f as described above, The oscillator 2 via the constant voltage circuit G
1 is configured to be supplied with power.

Here, the operation of the humidity detection device 17 in this embodiment will be explained.

First, when the humidity display mode is selected by operating the mode selection slide switch Sw and closing it with the terminal C, the AND circuit 20 is turned on. Therefore, in this state, when the sampling clock pulse φ1 is input from the clock signal forming circuit 16, the NAND circuit 29
becomes ON state, and the C-MOS ring oscillator 21 performs an oscillation operation. On the other hand, the clock pulse φ given at the timing near the rising edge of the pulse φ1
4, the frequency dividing circuit 23 and counter 24 are set. Furthermore, since the clock pulse φ2 is input to the AND circuit 22, the clock pulse φ2 is
The D circuit 22 is in the ON state, and during this period t, the oscillation output from the ring oscillator 21 is input to the frequency dividing circuit 23 via the AND circuit 22, and furthermore, the frequency divided output signal from the frequency dividing circuit 23 is input to the frequency dividing circuit 23. This will be input to the counter 24. Furthermore, a clock pulse φ for latch timing control is given at the falling timing of the pulses φ1 and φ2.
3 is the latch control signal input terminal 25a of the latch circuit 25
, the count contents of the counter 24 are latched into the latch circuit 25.

It is clear that the latched content is the capacitance Ch of the relative humidity detection element 6, that is, a digital value that changes depending on the relative humidity in the atmosphere.

By the way, in this embodiment, the above-mentioned capacitance Ch has a characteristic of increasing approximately linearly as the relative humidity increases, as shown in FIG. The capacity value Ch of 6 is the standard relative humidity H0 [%
If the capacitance value of the detection element 6 in ) is C0,
It is given by the following equation (2).

Ch=C0+A(H-H0) (2) where A is the slope of the straight line in the graph of FIG. 6 and is a constant determined by the detection element. In this case, if the capacitance value of the detection element 6 corresponding to relative humidity 0 [%] is C00, then Ch=AH+C00 (2
)′ expression. Similarly, if the capacitance value of the detection element 6 corresponding to a relative humidity of 100% is C100, then C10
0=100A+C00 (2)''.On the other hand, the number of pulses N included in the oscillation output signal output from the oscillator 21 via the AND circuit 22 over the predetermined time t is , N=f・t...Equation (3).From the above equations (1), (2)', and (3), the [%] value of relative humidity is calculated from the value of N. A formula for determining H can be derived.

Figure 8 is a graph showing the relationship between the values of N and H in equation (4), where N00 and N100 are the number of pulses N when the relative humidity is 0 [%] and 100 [%], respectively. It is a value.

N00=1/2.2C00R・・・(3)′ formula However, in FIG. 8, the value of N in the interval other than [N100, N00], that is, N such that H is 0 or less or 100 or more The range of values is a range that does not occur theoretically.

Here, assuming that the frequency of the divided output signal outputted after the frequency dividing circuit 23 divides the frequency of the oscillation output signal from the oscillator 21 is F, the frequency division ratio X of the frequency dividing circuit 23 is F=fX...・
Defining it using the equation (5), the number of pulses P output from the frequency dividing circuit 23 and input to the counter 24 over the above-mentioned time t is P=NX (6) The formula becomes Substituting this equation (6) into equation (4), it is clear that in this embodiment, the value of P is the content that is latched by the latch circuit 25, and based on the value of P in the latch circuit 25, , the relative humidity [%] value H is obtained by performing an arithmetic approximation calculation according to the above equation (7) in the humidity calculation block 26.

Further, based on the humidity calculation output signal h indicating the value of H outputted from the humidity calculation block 26, the relative humidity is displayed in units of [%] by the liquid crystal display device 1.

Note that the capacitance value Ch of the detection element 6 has a slight deviation from equation (2)', and the oscillation frequency f of the C-MOS ring oscillator 21 also has a slight deviation from equation (1). There is a slight possibility that, for example, the calculated value H of relative humidity will be 0 or more, or 100 or more under extreme conditions of dryness or humidity, but in that case, the calculation block 26 will set it to 0 [%]. Alternatively, it is preferable to output a signal indicating a value of 100 [%].

Next, FIG. 9 is a circuit diagram showing a second embodiment of the humidity detection device 17. Similar to the embodiment shown in FIG. 4, this embodiment uses a glass-ceramic thick film humidity detection element and can perform relative humidity calculations in [%] units with a relatively simple configuration. This was taken into consideration.

In this embodiment as well, the above-mentioned FIGS. 1 to 3 and 5 to 8 are applied as common explanatory diagrams, and the same numbers in FIG. 9 as in FIG. This indicates the same element.

In this embodiment, the humidity detection device 17 is composed of a C-MOS ring oscillator 21, a frequency dividing circuit 23, a down counter 44, a latch circuit 45, a limit value detection circuit 47, etc. The contents of the latch circuit 45 are as described below. The value remains as it is [
The structure is designed to approximate the relative humidity value in units of %]. However, the basic configuration, power supply, etc. of the C-MOS ring oscillator 21 are completely the same as in the case of FIG. 4 described above.

Next, the operation of the humidity detection device 17 in this embodiment will be explained.

First, when the humidity display mode is selected by operating the mode selection slide switch Sw and closing the switch Sw with the terminal C, the AND circuit 20
becomes ON state.

Therefore, in this state, when the sampling clock pulse φ1 is input from the clock signal forming circuit 16, the NAND circuit 29 is turned on for a period corresponding to the pulse width, and the C-MOS ring oscillator 21 oscillates. On the other hand, the clock pulse φ4 given at a timing near the rising edge of the pulse φ1
As a result, the frequency dividing circuit 23 is reset, the down counter 44 is initialized to a predetermined initial value Si, and the flip-flop circuits (hereinafter referred to as FF) 48 and 49 are also reset.

Further, since the clock pulse φ2 is input to the AND circuit 22, the AND circuit 22 is in the ON state for a period corresponding to the pulse width 1, and the oscillation output signal from the oscillator 21 is The signal is inputted to the frequency dividing circuit 23 via the AND circuit 22, and the frequency divided output signal from the frequency dividing circuit 23 is further inputted to the down counter 44.

Furthermore, a clock pulse φ3 for latch timing control is applied at the falling timing of the pulses φ1 and φ2.
is input to the latch control signal input terminal 45a of the latch circuit 45, the counted content value S of the down counter 44 is latched into the latch circuit 45. It is clear that this latched content value S is the capacitance value Ch of the relative humidity detection element 6, that is, a digital value that increases approximately linearly in accordance with the relative humidity in the atmosphere.

Here, in this embodiment, instead of using the humidity calculation block 26 to perform the calculation based on equation (7) as in the case of FIG. 4, by using the down counter 44, the [%] value of the relative humidity The configuration is such that H is approximated by a straight line S shown by a two-dot chain line in FIG. 10, and the approximate value is directly latched into the latch circuit 45.

In other words, FIG. 10 shows that in the graph of FIG. 8 mentioned above,
The interval of N [N100, N0
0], and the straight line S is (
This is a straight line passing through the two points N100, 100) and (N00, 0). Therefore, the equation of the straight line S is as follows. That is, in this embodiment, A within the above-mentioned time width t.
When the number of pulses included in the oscillation output signal output from the oscillator 21 via the ND circuit 22 is N,
In order to make the content value S of the down counter 44 equal to the value of S shown by the above equation (8), the frequency division ratio X of the frequency dividing circuit 23 and the above-mentioned initial set value Si of the down counter 44 are as follows. According to such a configuration, the latch circuit 45 is set to have a [%] value H of the relative humidity.
Since the above-mentioned value of S, which approximates , is latched as is, the latch circuit 45 has only to output the signal representing the above-mentioned value of S as it is as the humidity calculation output signal h.

Note that the above frequency division ratio
)'' expression can be calculated based on the values of C00 and C100, but the oscillator 2
The oscillation frequency f of 1 may actually deviate slightly from equation (1), so by finding the straight line S based on the actual measured value of N, the frequency division ratio X and the initial set value Si
It is more practical to determine

Also, in this example, under extreme dry or wet conditions,
Since the value of S may be less than 0 or more than 100, in that case, the latch circuit 45 is
In this embodiment, a limit value detection circuit 47 and FFs 48 and 49 are provided so that 0 or 100 is latched.

That is, as the frequency-divided output signal from the frequency dividing circuit 23 is counted down by the down counter 44, the content value S of the down counter 44 decreases from the initial set value Si, but when the content value S of the down counter 44 becomes 1.
00, first the output terminal 4 of the limit value detection circuit 47
One pulse signal is output from the output terminal 47b of the detection circuit 47, inverting the FF 48 to the set state, and when the content value S continues to decrease and reaches 0, one pulse signal is output from the output terminal 47b of the detection circuit 47, and the FF 49 is inverted. is configured to reverse the set state. In other words, if FF48 remains in the reset state, the above content value S becomes 10.
This means that the value remained above 0, and if up to FF49 were in the set state, it means that the content value S exceeded 0 and decreased.In both cases, theoretically This means that this is an impossible situation.

Accordingly, in this embodiment, when the content value S of the down counter 44 is latched in the latch circuit 45, the FF 48
is in the reset state, 1 instead of the above content value S
00, and when FF49 is in the set state, 0 is latched instead of the content value S, and 0 is set.
This is to ensure that values less than 100 or more than 100 are not displayed.

Note that in this embodiment, a variable resistor is used as the feedback resistor 27 constituting the C-MOS ring oscillator 21;
According to such a configuration, by adjusting the resistance value R of the feedback resistor 27, it is also possible to adjust the oscillation frequency f of the oscillator 21 as necessary.

Next, FIG. 11 is a circuit diagram showing a configuration example of a humidity detection device 17 having better approximation accuracy than the embodiment shown in FIG. 9 described above. Also for this example, the above-mentioned FIGS. 1 to 3 and FIGS. 5 to 8 are applied as common explanatory diagrams,
In FIG. 11, the same numbers as in FIG. 4 or FIG. 9 indicate the same elements.

In this embodiment, the humidity detection device 17 includes a C-MOS ring oscillator 21, a variable frequency dividing circuit 43, a down counter 44,
It is composed of a latch circuit 45, a limit value detection circuit 47, a frequency division ratio setting circuit 50, etc. In this embodiment as well, the content value of the latch circuit 45 is configured to directly approximate the humidity value in [%] units. ing.

Note that the C-MOS ring oscillator 21 in this embodiment is as follows:
It has exactly the same configuration as the oscillator 21 in the case of FIG. 9, and a glass-ceramic thick film humidity detection element is used as a charge/discharge capacitor in CR type oscillation. Further, the operation of the humidity detection device 17 of this embodiment is similar to the operation in the case of FIG. 9, but the difference is that the oscillation output signal outputted from the oscillator 21 via the AND circuit 22 is The frequency is divided by the variable frequency dividing circuit 43, and the frequency is divided according to the content value S of the down counter 44 that counts the frequency divided output signal from the variable frequency dividing circuit 43 in a down count mode. The frequency ratio setting circuit 50 is the variable frequency dividing circuit 4
The structure is such that the frequency division ratio of 3 is appropriately controlled.

As a result, in this example, as shown in FIG. 12, the curve showing the [%] value H of relative humidity in FIG. 8 is approximated by several straight lines S1 to S4. Become.

Next, the operation will be explained with respect to points that are different from the case of FIG. 9. However, in the following explanation, N75, N50, N
25 has relative humidity [%] values of 75, 50, and 50, respectively.
This is the value of N shown in the above-mentioned equation (3) when 25.

First, in this example, when the relative humidity is 75% or higher, as shown in FIG. The configuration is such that it is determined by approximation using a passing straight line S1.

The equation of this straight line S1 is, therefore, in this embodiment, within the above-mentioned time width t,
Until the number of pulses included in the oscillation output signal output from the oscillator 21 via the D circuit 22 reaches N75, the content value S of the down counter 44 is equal to the value of S1 shown by the above equation (11). In order to be equal, the frequency division ratio X1 of the variable frequency dividing circuit 43 and the initial set value Si of the down counter 44 are set to be equal to each other.

That is, in this embodiment, when the value of N is equal to or less than N75, in other words, when the content value S of the down counter 44 is equal to or less than 75, the division ratio setting circuit 50 sets the division ratio of the variable frequency division circuit 43 to the above-mentioned value. X1 (straight line S1
In other words, it is controlled so that the slope is as follows.

Similarly, the [%] value of relative humidity is 75~50, 50~
25, and the range of 25 to 0, that is, the value of N is N75 to
In the ranges of N50, N50 to N25, and N25 to N00, the values of H are approximated and determined using straight lines S2, S3, and S4, as shown in FIG. 12. However, straight lines S2, S3, and S4 have two points (N75, 75) and (N50,
50), (N50, 50) and (N25, 25), or (N25, 25) and (N00, 0), respectively.

That is, in this embodiment, when the content value S of the down counter 44 reaches 75 due to the value of N reaching N75, the frequency division ratio of the variable frequency dividing circuit 43 becomes X2, which is indicated by the slope of the straight line S2. The frequency division ratio setting circuit 50 controls the frequency division ratio setting circuit 50 so that .

Here It is.

Similarly, when the value of N reaches N50 and the content value S of the down counter 44 reaches 50, the division ratio setting circuit 50
sets the frequency division ratio of the variable frequency divider circuit 43 to X3, which is equal to the slope of the straight line S3.

Here It is.

Similarly, when the value of N reaches N25 and the content value S of the down force counter 44 reaches 25, the variable frequency dividing circuit 4
The frequency division ratio of 3 is controlled to be a value X4 equal to the slope of the straight line S4.

Here It is.

As described above, in this embodiment, the down counter 4
By configuring the frequency division ratio setting circuit 50 to appropriately control the frequency division ratio of the variable frequency division circuit 43 according to the content value S of 4, the [%] of the relative humidity shown in FIG. It is possible to approximate the curve indicating the value H with the four straight lines S1 to S4 shown in Figure 12, and as a result, the curve is even more approximate than in the case of Figure 9. A highly accurate approximate value of H is latched into the latch circuit 45.

Note that each value of N100, N75, N50, N25, and N00 in the above equations (12), (14), (15), and (16) is obtained by calculation, so in the end, the frequency division ratio of each range is calculated. The values of X1 to X4 shown can also be obtained by calculation, but in reality, the oscillation frequency f of the oscillator 21 deviates from equation (1), so it is calculated based on the actual value of N. , it is more practical to obtain the frequency division ratios X1 to X4.

Furthermore, in the above embodiment, the H value range from 0 to 100 is divided into four straight lines S1 to S4 for approximation, but it is approximated by dividing it into four or less or four or more straight lines. It is clear that this can also be done, and the greater the number of divisions, the higher the approximation accuracy will be.

Furthermore, in the above embodiment, the frequency division ratio setting circuit 50 is configured to control the frequency division ratio of the variable frequency division circuit 43 according to the content value of the down force counter 44, but as shown in FIG. Another counter 51 is provided for counting the frequency-divided output signal from the variable frequency divider circuit 43.
It is clear that the frequency division ratio setting circuit 50 may be configured to set the frequency division ratio of the variable frequency division circuit 43 according to the count value of 1. Note that FIG. 13 shows the same elements as FIG. 11.

As described above, according to the present invention, relative humidity can be measured digitally by using a C-MOS ring oscillator that uses a relative humidity detection element having relative humidity/capacitance conversion characteristics as a charge/discharge capacitor in CR type oscillation. Because it is configured to convert to a value, it is possible to convert digital values according to changes in relative humidity values without configuring a bridge circuit or using a general analog-to-digital conversion circuit as in the past. This makes it possible to realize a compact and low power consumption humidity detection device.

In the above-mentioned embodiments, power is supplied to the C-MOS ring oscillator from the power supply battery via a constant voltage circuit. It becomes possible to eliminate the influence that fluctuations in the electromotive voltage of the power supply battery due to change or aging have on the C-MOS ring oscillator.

In other words, the C-MOS that constitutes the C-MOS ring oscillator
The internal resistance of an inverter (or NAND circuit) has characteristics that vary slightly depending on the supply voltage.
If the supply voltage fluctuates, the oscillation frequency will also fluctuate accordingly, but if a constant voltage circuit is provided as described above, the supply voltage to the oscillator will be stable and measurement accuracy will be improved.

Furthermore, in the above embodiment, the crystal oscillation circuit for the clock function is also configured to be supplied with power from the constant voltage circuit, or if such a configuration is used, the clock signal for sampling control is supplied with power. Fluctuations in frequency and pulse width can also be suppressed.

That is, the above clock signal is formed based on the oscillation output signal of the crystal oscillator circuit, and the oscillation frequency of this crystal oscillator circuit also has a characteristic that it fluctuates slightly according to fluctuations in the supply voltage. The oscillation frequency is also stabilized by the intervention of the constant voltage circuit, and as a result, the clock signal formed based on the oscillation output signal also becomes stable.

Therefore, for example, the sampling time width given by the pulse width 1 of the sampling control clock signal φ2 is also stabilized at a constant value, making it possible to further improve the humidity detection accuracy. On the other hand, in the case of a configuration in which the above-mentioned time width also fluctuates due to the influence of fluctuations in the electromotive voltage of the power supply battery, the measurement accuracy will decrease accordingly.

Further, as in the case of the above-mentioned embodiment, when using a detection element whose capacitance value decreases as relative humidity increases, such as a glass-ceramic thick film humidity detection element, a down-counting means is used. Accordingly, if the signal from the C-MOS ring oscillator and the frequency dividing circuit is configured to be counted, the counted value of the down-counting means will also increase in accordance with the increase in relative humidity. It is also possible to perform the conversion relatively easily.

In that case, if the humidity detection element is an element whose characteristics change due to the influence of temperature, the temperature of the environment is detected and the initial set value of the down-counting means is appropriately set according to the detection result. It is possible to perform temperature compensation relatively easily by changing the temperature.

In addition, in the above-mentioned embodiment, the period of the sampling operation in which the humidity detection position 17 detects the relative humidity, that is, the C-MO
The period T of the clock pulse φ1 for causing the S-ring oscillator 21 to perform the sampling operation can be appropriately determined according to various needs, and the period of the sampling operation can also be selected by an external operation switch. Alternatively, it is also possible to configure the sampling operation so that one sampling operation is performed each time an external operation switch such as a mode selection switch is operated.

[Brief explanation of the drawing]

1 to 8 are diagrams showing a clock calculator equipped with a humidity detection device according to an embodiment of the present invention. FIG. 1 is a plan view showing its appearance, and FIG. A sectional view showing the housing part, FIG. 3 is a block diagram showing the outline of the circuit configuration,
Figure 4 is a circuit diagram showing the humidity detection device, Figures 5 and 6
The figure is a plan view showing a schematic structure of a glass-ceramic thick film humidity detection element, and a graph showing relative humidity/capacitance conversion characteristics; FIG. 7 is a time chart showing each clock signal supplied to the humidity detection device; FIG. 8 is a graph for explaining this embodiment. 9 and 10 show a second embodiment of the present invention, in which FIG. 9 is a circuit diagram showing the configuration of a humidity detection device, and FIG. 10 is a graph for explaining this embodiment. 11 and 12 are diagrams showing a third embodiment of the present invention, in which FIG. 11 is a circuit diagram showing the configuration of a humidity detection device, and FIG. 12 is a graph for explaining this embodiment. FIG. 13 is a block diagram showing a partial modification of the humidity detection device shown in FIG. 11. 1...Liquid crystal display device, 4...Receiving section for humidity detection element, 6...
・Humidity detection element, 11... Crystal oscillation circuit, 12... Frequency dividing circuit, 13... Time counter, 16... Clock signal forming circuit, 17...
... Humidity detection device, 18 ... Display control circuit, 21 ... C-MOS ring oscillator, 23 ...
...Frequency divider circuit, 24...Up counter, 25...Latch circuit, 26...Humidity calculation block, 43...Variable frequency divider circuit, 44... Down counter, 45... Latch circuit, 50... Division ratio setting circuit, E... Power supply battery, G...・Constant voltage circuit, Sw...Slide switch for mode selection.・(1.
Co., Ltd. (,'):,,,'-□11 Figure 1 Figure 2 Figure 3 514 Figure 6 Figure 7

Claims (3)

[Claims] (1) A humidity detection device comprising a relative humidity detection element for detecting relative humidity, and a conversion circuit for converting the detection result by the detection element into digital value data and outputting it, The detection element is composed of an element having a relative humidity/capacitance conversion characteristic in which the capacitance value changes depending on the relative humidity in the atmosphere, and the conversion circuit makes the detection element a charge/discharge capacitor in CR type oscillation. C-MOS
A humidity sensing device comprising at least a ring oscillator. (2) The relative humidity detection element is composed of an element whose capacitance value increases approximately linearly as the relative humidity increases, and the conversion circuit inputs the signal output from the C-MOS ring oscillator. a frequency divider circuit, and a down-counter whose input is a signal output from the frequency divider circuit,
The signal output from the C-MOS ring oscillator is frequency-divided and down-counted by the frequency dividing circuit and the down-counting means within a certain period of time determined by the sampling signal from the sampling signal forming means. The humidity detection device according to claim 1, characterized in that: (3) The humidity detecting device according to claim 2, wherein the relative humidity detecting element is comprised of a glass-ceramic thick film humidity detecting element.