JPS6136618B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a humidity transmitter that is not affected by ambient temperature.

The purpose of the present invention is to measure humidity unaffected by temperature changes, especially when the temperature of the atmosphere to be measured changes in the range of 0°C to 50°C, and is suitable for use in centralized air conditioning. It is suitable for a device for transmitting a temperature-compensated humidity signal from a detection unit to a central device or the like.

Another object of the present invention relates to a device for preventing the effects of polarization caused by direct current components, and particularly to a device for preventing the cause of direct current generation based on the difference in output resistance when a semiconductor is turned on and off in an electronic circuit. .

In measuring humidity, it is known that the reference voltage applied to an electrical humidity sensing element produces different outputs based on the humidity sensing resistance value, and that a polarization effect occurs when a direct current component is applied to the humidity sensing element. It is being The generation of DC components not only gives an error to the detected humidity value, but also destroys the electrical characteristics of the humidity sensing element.
Various improvements have been attempted in conventional devices to prevent this. A sine wave AC voltage is applied as a reference power source at a commercial frequency or a higher frequency, and the voltage applied to the moisture sensing element is at a commercial frequency or higher. , or more, it alternates to prevent the generation of DC components. In the present invention, the humidity is detected together with the ambient temperature to be measured, and a reference voltage generator is provided in which the positive 1/2 period and the negative 1/2 period are equal in one period, and The moisture-sensitive resistor has a capacitor R _C connected in series to prevent polarization.

One feature of the present invention is that a voltage from a common reference voltage generator is used as the reference voltage given to each resistance type detector for temperature and humidity of the atmosphere to be measured, and resistance values based on changes in temperature and humidity are used. The changes generate electrical signals of temperature and humidity, respectively. These electrical signals are taken out separately and amplified by separate amplifiers. The outputs of the two amplifiers are fed to an adder/subtractor which allows temperature compensated signal values to be transmitted to separate locations as an analog pulse period.

In an embodiment of the present invention, the reference voltage generator generates an alternating voltage having equal positive and negative 1/2 periods at a commercial power supply frequency or a certain range of frequencies lower than it.
A temperature sensing element and a humidity sensing element are respectively provided. For example, the reference voltage frequency is 20Hz to 60Hz, the moisture sensing element is made of oxide metal resistor or lithium chloride, and the above-mentioned alternating voltage is applied between a pair of electrodes, causing a current of, for example, 200 microamperes or less to flow. .

In FIG. 1, 1 and 2 indicate the two amplifiers mentioned above, and the outputs of amplifiers 1 and 2 become inputs to one operational amplifier 3. _VR is a reference voltage generator having the characteristics described above, and the temperature sensitive resistor R _T and the humidity sensitive resistor R _H are connected in parallel to receive the voltage from the reference voltage generator _VR . R ₁ and R ₂ are adjustment resistors, and R _C is a capacitor for preventing polarization. The reference voltage is applied to the temperature-sensitive resistor R _T via the adjusting resistor R ₂ , and to the humidity-sensitive resistor R _H via the adjusting resistor R ₁ and the anti-polarization capacitor R _C . The respective outputs based on the resistance value changes of the temperature sensitive resistor R _T and the humidity sensitive resistor R _H become inputs to amplifiers 1 and 2, which generate analog detected values regarding the temperature and humidity in the atmosphere. 4 indicates a zero volt line, which is connected to the positive inputs of amplifiers 1 and 2 and operational amplifier 3, and variable resistor R ₄ is connected between zero volt line ₄ and inverter 5 via resistor R 3. The sliding terminal 6 of the variable resistor R ₄ is a zero adjustment terminal.

Moisture sensing element R _H (R _H
The conductance (μ) of MΩ can be exemplified by equation (1).

Y=1/R _H =0.250H+0.0388T _F -3.60(μ) ......(1) However, H...Relative humidity (% _RH ) T _F ...Ambient temperature (〓) Temperature sensing element R _T The resistance value (referred to as R _T Ω) can be expressed by equation (2).

R _T =466.214+1.337T _F (Ω) ......(2) Referring to Figure 1, calculate the output voltage of operational amplifier 3 as V ₀
Let V _R be the voltage generated by the reference power supply V _R .

V ₀ =V _R (R ₁ /R ₁ +R _C +R _H -1/M・R _T /(
R ₂ +R _T ) +R ₄ /R ₃ +R ₄ )K......(3) However, K...gain M...constant Here, equation (1) is changed to equation (4), and equation (2) Rewrite as equation (5).

Y=1/R _H =αH+βT-γ (4) R _T =A+QT (5) Furthermore, assuming that R ₁ +R _C <<R _H and R ₂ +R _T =R _K , (3 ) can be converted as shown in equation (6).

V ₀ =V _R {R ₁ (αH+βT-γ) −A+QT/M・R _K +R ₄ /R ₃ +R ₄ }K = V _R {R ₁ αH+(R ₁ β−Q/M・R _K )T + (R ₄ /R ₃ +R ₄ -R ₁・γ-A/M・R _K )}K
......(6) Here, set the circuit constants so that R ₁ β-Q/MR _K = 0 R ₄ /R ₃ +R ₄ -R ₁ γ-A/MR _K = P (6) Rewrite the equation as equation (7).

V ₀ = V _R (R ₁ αH + P) K = V _R・R ₁・α ・K・H + V _R・P・K ………(7) Equation (7) is the temperature-resistance change of the temperature sensing element R _T This circuit is a suitable example because the output characteristics are unrelated to the characteristics, and the above-mentioned circuit constants can be easily selected in the temperature range of 0° C. to 50° C. In particular, a common reference power supply voltage is applied to the temperature-sensitive resistor R _T and the humidity-sensitive resistor R _H , respectively, and the outputs generated at the resistors _RT and R _H become inputs to amplifiers 1 and 2, respectively. Amplifier 1
The respective outputs of 2 and 2 become the inputs of the amplifier 3, are subjected to addition and subtraction operations, and are applied to the analog pulse period converter 7 to convert the humidity measurement value of the atmosphere to be measured into a temperature change in the range of 0°C to 50°C. It can be extracted as a pulse periodic signal with a value that is not affected by the

FIG. 2 illustrates conventional characteristics of moisture-sensitive resistance when lithium chloride is used. The conductance Y is plotted on the vertical axis in μ and the relative humidity H is plotted on the horizontal axis in %, and the characteristics in a stable state are expressed by a solid line. The dotted lines indicate hysteresis characteristics, the dotted line e indicates the case where the atmospheric humidity increases, and the dotted line f indicates the case where the atmospheric humidity decreases. The humidity detection characteristics of this device are as follows: In a stable state, the output voltage is
V ₀ appears almost linearly with respect to humidity. In order to ensure that the output voltage V ₀ does not include a temperature change factor, to cancel out the temperature change factor or make it a negligible value, and preferably to be linear in the range of 0°C to 50°C. Then, the values of each of the elements are selected and wired into an electrical circuit.
In order to further enhance the effects of the present invention, a variable resistor R is used to provide zero compensation to the outputs of the amplifiers 1 and 2, or to set the temperature-sensitive resistor R _T to a reference value, that is, a value at a specific temperature. ₄ can be adjusted.
An inverter 5 is connected in series with the resistors R ₄ and R ₃ , and the inverter 5 is connected to a common node with the resistor R ₁ as shown. When using a C-MOS semiconductor flip-flop circuit, a DC component is generated in the electrical circuit due to the difference in output on/off resistance at on/off times, and even if the reference voltage is applied as the desired voltage, a DC component is generated. However, since it is applied to the moisture sensitive element, it increases the cause of the above-mentioned polarization effect. Although the cause of the generation of such a DC component has been described in the case of a C-MOS semiconductor as an example, there are also factors that occur in electrical circuits that are often used in designing, and this is a problem that must be taken into consideration.
In order to prevent the generation of such a DC component, this device connects a capacitor R _C having an appropriate value in series with the humidity sensing resistor R _H to block the DC component. Furthermore, in order to make the aforementioned temperature effects irrelevant, the respective outputs of the humidity sensitive resistor R _T and the humidity sensitive resistor R _H become inputs to an amplifier 1 and another amplifier 2, respectively. Preferably, the capacitor R _C is directly connected in series with the humidity sensitive resistor R _H . In order to make temperature effects irrelevant, the values of each element are selected and connected to derive the above equation (7). Each circuit constant can be obtained by solving equation (7). Here the relative humidity H is 0%.
It shall vary within a range of 100%. When the humidity changes from 0% to 100%, the output voltage in one embodiment is 0.375 volts and 1.375 volts, and the output change per temperature is 1.55% for 1 volt.
It is below FS. The reference voltage V _R is used as a common power source for the temperature sensitive resistor _RT and the humidity sensitive resistor R _H , and for example, it is not within the scope of the present invention when different power supplies are used for the temperature sensitive resistor _RT and the humidity sensitive resistor R _H. . Reference value power supply V _R
The positive and negative half-cycles in one cycle are equal, and an alternating voltage with an equal integral amount is applied to the humidity-sensitive resistor R _H between the positive and negative half-cycles. The above-mentioned frequency is repeatedly applied to the humidity-sensitive resistor _RH , and the DC component generated in the electric circuit is prevented from being applied to the humidity-sensitive resistor _RH by the capacitor _RC . The characteristics of the capacitor R _C must satisfy the above-mentioned conditions for selection of constants in order to block direct current and change the influence of temperature changes.

As described above, in the present invention, the reference voltage is divided and supplied to the temperature sensing element, and the reference voltage is also divided and supplied to the humidity sensing element connected in parallel to the temperature sensing element. In a temperature change range of 50°C, the above is suitable for compensating for temperature effects on the humidity sensing element and preventing direct current from being applied to the humidity sensing element, regardless of the temperature-resistance change characteristics of the temperature sensing element. Each value is selected in order to construct an electric circuit and to obtain constants in the electric circuit stably and easily.
For this purpose, the reference power supply applies voltages with equal positive and negative half cycles to the temperature sensing element and the humidity sensing element, respectively, and a capacitor R _C is connected in series to the humidity sensing element R _H. The output based on the resistance value change becomes the input to amplifiers 1 and 2, and amplifier 1
The outputs of 2 and 2 are applied to an amplifier 3 for addition and subtraction operations, and the outputs are also applied to an analog pulse period converter so that a pulse period signal can be transmitted to a remote location.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an electrical circuit according to an embodiment of the invention. FIG. 2 is a graph showing the relationship between relative humidity and interelectrode conductance of a lithium chloride moisture-sensitive element. 1, 2, 3... Amplifier, 4... Zero volt line, 5
...Inverter, 6... Sliding contact, R _T ... Temperature-sensitive resistor, R _H ... Moisture-sensitive resistor, R _C ... Capacitor, R ₁ , R ₂ , R ₃ , R ₄ ... Resistor, V _R ...Reference power supply.

Claims (1)

[Claims] 1 A temperature-sensitive resistor and a polarization prevention capacitor are connected in series to measure the temperature of the atmosphere to be measured by dividing a reference voltage with equal positive and negative half cycles to measure the humidity of the atmosphere to be measured. The output based on the resistance value change of the temperature sensitive resistor is supplied to the amplifier 1, and the output based on the resistance value change of the humidity sensitive resistor is supplied to the amplifier 2. The outputs of the amplifiers 1 and 2 are added and subtracted by the amplifier 3, and the resistance value of each element is selected and increased so as to remove the variable element that shifts depending on the temperature of the humidity element. The output of the width filter 3 is supplied to an analog pulse period converter to convert the humidity measurement value of the atmosphere to be measured to 0°C.
A humidity transmitter characterized in that the humidity signal is extracted as a pulse cycle signal with a value that is unaffected by temperature changes in the range of 50 to 50 degrees Celsius.