JPS6022736B2 - hygrometer - Google Patents

Description

[Detailed description of the invention] The present invention relates to a hygrometer.

The present invention relates to an electronic hygrometer for measuring humidity in a wide range when the temperature changes. It is capable of detecting the resistance value based on the humidity and temperature of the measurement target using each of the variable resistance elements, and continuously converting the temperature-related hygrometer value into a high-speed pulse cycle, and is particularly suitable for large numbers of measurements. Suitable for use in centrally controlled air conditioners that sample objects.

In the humidity measurement target of the present invention, as shown in FIG. 3, a humidity-resistance variable element whose resistance value is represented by Rh and a temperature-resistance value variable element whose resistance value is represented by Rt are connected in series. There. Both elements Rh and Rt are provided on a common measurement object and produce resistance values based on humidity and temperature at the same time. eh and ct are power supplies for elements Rh and Rt'; R, , R2, R3, R4, R5, R6 and C are resistors and capacitors of appropriate values connected as shown. Relative humidity day at temperature T (
RH%) and the measured conductance have approximately the following relationship.

Y=K, H+K2T+K3・”...[1} Here, Y: Conductance [French ○] H: Relative humidity [%RH] T: Temperature GF] K, , K2, K3 are constant power supply et force in the direction of the arrow At a certain time, the current lt flowing through the element Rt has the following relationship.

lt=R2. R, - RtR3 et = R2 minus - Rt). et--. ．． -. [2} However, for simplification, R2 and R3 are set to the same value. However, to simplify △, R2 = R3 and R4 + R
If we set 50R6=RL, △=2・R21RL(Rt+
R,) ten foxes2・R,・RttenR22(Rt+R,)=R
2 {(Rt 10R,) (sphere L+R2) 10th order, ・Rt}...
...[3'{If lt is calculated from the result of formula 31, (R, -Rt). e lt death (Rt+R,) (2RL+R2) 12R,・Rt
(R, 1Rt)・et. …． (4) R
t(2RL+R2+2R,)+2R, RL+R, R2 Letting the voltage appearing across the voltage dividing resistor R6 at the time of measurement of the element Rt be Vt, the following equation holds.

Vt=lt·R6...[5] Therefore, the voltage Vt can be determined from the relationship between each constant resistance value and the variable resistance value Rt.

On the other hand, for the value on the hygrometer side, the current flowing through element Rh is lh,
When the phase of the power source eh is in the direction of the arrow, the relationship is approximately expressed by the following equation.

However, assuming that R2=R3R, Rt, and the voltage Vh appearing across the voltage dividing resistor R6 when measuring the element Rh, the following equation holds.

Vh Ni1h. R6. 、． (6) Therefore, the voltage Vh can be determined from the relationship between the constant value and the variable resistance value Rh.

In order to prevent polarization of the humidity-resistance variable element Rh such as lithium chloride, AC power sources are used as the power sources eh and et.

Then, by applying a constant voltage to the elements Rh and Rt, and adding or subtracting the currents lh and lt flowing at that time, a temperature-compensated humidity-related voltage is generated across the resistor R6 from the relationship shown in equation (1). appear. Then, the value is read by the sample hold circuit 1 during the time when a voltage at a certain level is applied, and the high-speed pulse cycle is continuously sent to the output terminal 3 by the millivolt-to-pulse conversion circuit 2 as a temperature-compensated relative humidity measurement value. Output. Next, a more specific example will be explained.

In FIG. 1, a transformer 4 has secondary coils 5, 6, and 7 that generate appropriate voltages. Coil 5 is connected to a power source et, and coil 6 is connected to a power source eh as described above.

The coil 7 is supplied to the circuit IC3 via a constant voltage diode B. Z.・Z2・Z.・Z22, Z phantom, and Z2 are Zener diodes, which are connected as shown in the figure, and each Zener diode thus provides the effect described later. This embodiment has a common AC power supply, and each circuit is provided with an appropriate voltage. In order to apply a sine wave from an AC power source to elements Rh and Rt' at a constant voltage, the voltage from coils 5 and 6 is applied to the energizer diode Z2.・
Z22・Z3. - A voltage as shown in FIG. 2A is applied to each of the clipping elements Rh and Rt by Otsu 2.

Then, a predetermined time X, . A desired constant voltage is applied to elements Rh and Rt only during this period. At this time, the voltage VR6 generated across the resistor R6 is as shown in FIG. This time x. ．． Let be the effective measurement time. In addition, the Zener diode Z, .・Z2 is a diode for overvoltage prevention. The voltage appearing across this resistor R6 is input to the sample and hold circuit 1 in FIG.
In FIG. 1, this sample and hold circuit is
2, IC3, IC4, and other resistive capacitors, etc., and the voltage from coil 7 is a half-wave trapezoidal wave biased by VN from the 0 point by Jenner diode Z4.
As a result, inputs A and B of IC4 appear ON and OFF alternately and inversely to each other so as to change the state of IC4. In addition, IC3
diodes D connected in opposite directions in parallel to the inputs of
I and D2 are for overvoltage input protection of IC3. Therefore, the voltage VQ of the input A sphere changes as shown in FIG. 2C, and the effective measurement time X, . A timing time X22 for sampling and holding is generated within.

On the other hand, the voltage VR6 generated across the resistor R6 is
and a resistor, the output is amplified so that it can be input to the sample and hold circuit, and the output is
The sample is held. Then, the voltage output of IC2 appears at output 8 via a filter circuit consisting of resistor 7 and capacitor CI. This resulting voltage output is applied to the millivolt pulse generator 2 shown in FIG. 1, which ultimately provides a temperature compensated humidity measurement value at the output terminal 3 as a pulse output. The clipping levels for clipping the voltages from coils 5 and 6 are different, and the effective measurement time for each, that is, the effective measurement time for elements Rh and Rt is:
May be different.

In that case, sampling will be performed within the shorter effective measurement time. As shown in FIG.
Let the effective measurement times of t be X', 2 and X', . Thus, the sampling timing time X'22 is generated within the shorter effective measurement time, that is, the time X',2 in this case. Time X′, . The values of and X', 2 are set to appropriate values depending on the type and combination of the humidity sensing element and temperature sensing element, and the object to be measured.

As described above, according to the present invention, a constant voltage is applied to the elements Rh and Rt for a predetermined time, that is, an effective measurement time, and the current flowing through each element, which changes depending on humidity and temperature, is detected as a voltage by the resistance element. On the other hand, the sample-and-hold circuit samples and holds the voltage across the resistance element within the predetermined time.

Then, the conversion circuit converts the sampled and held value into
Since the temperature-compensated hygrometer value is output in pulses, it is extremely effective for high-speed processing in air conditioner measurement systems.

[Brief explanation of drawings]

The figures show an embodiment of the present invention; FIG. 1 is a schematic circuit diagram, FIGS. 2 and 4 are waveform diagrams, and FIG. 3 is a specific partial circuit diagram of FIG. 1. 1... Sample hold circuit, 2... Millivolt to pulse converter, Rt... Temperature-resistance variable element, Rh...
...・Humidity-resistance change element. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A humidity-resistance change element, a temperature-resistance change element, and a voltage from an AC power supply applied to a constant voltage for a predetermined time to each of the humidity-resistance change element and the temperature-resistance change element. A power circuit that clips and supplies the above humidity -
a resistance element for detecting changes in the current flowing through the resistance change element and the temperature-resistance change element; a sample and hold circuit that samples and holds a voltage generated across the resistance element within the predetermined time; Humidity characterized by comprising a conversion circuit that converts the sample-held value of the sample-and-hold circuit into a high-speed pulse cycle output and outputs the same, and outputs a temperature-compensated humidity measurement value at a high-speed pulse cycle. Total.