JPS6022393B2 - humidity detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel device capable of converting an AC input signal into DC and logarithmically converting it.

Conventionally, when converting an AC input signal to DC and logarithmically converting it, as shown in FIG. Since this was done by connecting the operational amplifier 12 in series, it was necessary to use a plurality of operational amplifiers. The present invention enables AC-DC conversion and logarithmic conversion to be performed simultaneously by using only one operational amplifier, and will be described in detail below with reference to the accompanying drawings showing embodiments.

FIG. 2 shows an embodiment of the humidity detection device of the present invention, in which an alternating current input section A detects humidity, and an alternating current input unit A that outputs an alternating current corresponding to the humidity of the atmosphere. It is comprised of a logarithmic conversion/AC-DC voltage converter B that performs logarithmic conversion, rectification, and converts to DC voltage and outputs it.

The AC current input section A is constructed by connecting a capacitor 2 and a humidity sensing element 3 in series to the output terminal of an AC voltage generator 1, and inputs the AC voltage whose DC component is blocked by the capacitor 2 to the humidity sensing element 3. By converting it into an alternating current, an alternating current corresponding to the humidity is supplied to the next stage.

Logarithmic conversion/AC current/DC voltage converter B connects the non-inverting input terminal of the operational amplifier 4 to the ground terminal, connects the cathode of the rectifying diode 6 to the output terminal, and connects the inverting input terminal and the A feedback diode 5 for logarithmic conversion and temperature compensation is connected between the anode of the diode 6 and the anode so that the anode is on the inverting input terminal side.

Furthermore, a diode 7 for protecting the moisture sensing element 3 is connected between the inverting input terminal and the output terminal of the operational amplifier 4 so that its cathode is on the inverting input terminal side.

Note that 8 is a resistor connected between the anode of the diode 6 and the ground terminal, and 9 is a capacitor. The operation of the humidity detection device having the above configuration is as follows. By applying the AC power generated by the AC oscillator 1 to the humidity sensing element 3 via the capacitor 2, the voltage waveform on the input side of the humidity sensing element 3 becomes as shown in FIG. It is given as a pure alternating voltage as shown in .

This is to prevent the humidity sensing element 3 from losing its function due to polarization occurring when a DC component is applied since the electron conduction mechanism in the humidity sensing element is mainly based on ionic current. When the pure AC power obtained in this way is applied to the humidity sensing element 3, an AC current having information that changes depending on the degree of humidity sensitivity is taken out at the output side, and the inverting input terminal of the arithmetic multiplication circuit 4 is input.

Therefore, on the output side of the arithmetic multiplication circuit 4, a half-wave rectified waveform obtained by the diode 7 and a rectangular wave obtained by the logarithmic characteristic of the logarithmic diode 5 and the rectifying diode 6 are alternately provided as shown in FIG. A voltage waveform as shown in b is generated, and the voltage waveform shown in FIG. An output voltage Vo as shown in FIG. 3d is obtained. Incidentally, if the resistor 8 and capacitor 9 are not provided, the voltage waveform will be as shown in FIG. 3c. Furthermore, the diode 5 also plays the role of temperature compensation for changes in resistance value due to changes in ambient temperature of the green sensitive element 3.

Therefore, the smoothed DC voltage changes depending on the external humidity, and it is also possible to control the humidity by applying the DC voltage to a predetermined humidity control device (not shown). be.

Note that the diode 7 serves to protect the humidity sensing element 3, and when the diode 7 is not present, a half-wave rectified (DC) signal is applied to the humidity sensing element 3. Since the element 3 causes a polarization phenomenon as shown in FIG. In the device shown in FIG. 2, if all the diodes are connected in a reverse magnetic manner, the output characteristics will be opposite to those described above. In addition, by replacing the humidity sensing element 3 with a fixed resistor in FIG. 2 and applying an alternating current voltage to the connection point between the capacitor 2 and the fixed resistor, a direct current corresponding to the alternating voltage can be applied.
A logarithmically converted voltage is output.

The humidity detection device of the present invention as described above inputs an alternating current voltage of a predetermined frequency and voltage to a humidity sensing element which is an impedance element through a capacitor, and converts it into an alternating current in the humidity sensing element, which is logarithmically Conversion: The AC current is converted by a DC voltage converter, and the change in resistance value corresponding to the humidity of the humidity sensing element's atmosphere is obtained as an almost linear output characteristic, and the fluctuation due to the temperature of the humidity sensing element is converted logarithmically. The voltage-current transition characteristics associated with temperature changes in the diode for use with the circuit compensate for temperature changes in the atmosphere to a certain extent, and stable output characteristics can be obtained.Moreover, since only one operational amplifier is required, the configuration This is an excellent invention as it can simplify the process and provide it at low cost.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, Fig. 1 is an electrical wiring diagram showing a conventional example, Fig. 2 is an electrical wiring diagram of a humidity detecting device equipped with the device of the present invention, and Fig. 3 a shows a capacitor 2 and A waveform diagram at the connection point with the wet element 3, a voltage waveform diagram at the output terminal of the operational amplifier 4, and a voltage waveform diagram at the anode of the diode 6 without the resistor 8 and capacitor 9. d is the diode with resistor 8 and capacitor 9
Voltage waveform diagram at the anode of node 6, 4... operational amplifier, 5, 6, 7... diode. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 An AC input section A that inputs an AC voltage of a predetermined frequency and voltage and converts it into an AC current proportional to a change in resistance value corresponding to the atmospheric humidity of the humidity sensing element or other impedance element 3, and an output terminal of the operational amplifier 4. A feedback diode 7 is connected between the inverting input terminal and the inverting input terminal, and a rectifying diode 6 is connected in series with the anode side facing the output terminal side, and a rectifying diode 6 is connected in series with the cathode side facing the output terminal side of the operational amplifier 4. A feedback diode 5 for logarithmic conversion is connected in parallel with both diodes 6 and 7 between the side and the anode side of the diode 6 with the polarity reversed, and a A humidity detection device comprising a logarithmic conversion/AC current to DC voltage conversion device B, in which one end of a smoothing resistor 8 and a capacitor 9 are connected, and the other end of the resistor 8 and capacitor 9 is grounded. .