The working principle of humidity resistance and its application (III)

Humidity resistance application:

Humidity-sensitive resistors are widely used in household appliances, such as washing machines, air conditioners, video recorders, and microwave ovens, as well as in industrial and agricultural fields for humidity detection and humidity control.

A multivibrator is composed of a 555 time base circuit, a humidity sensor CH, and the like, and a capacitor C2 is connected to the output of the oscillator, which transforms the square wave signal output from the multivibrator into a triangular wave. When the relative humidity changes, the capacitance of the humidity sensor CH will change, which will cause the frequency of the output of the multivibrator and the amplitude of the triangle wave to change correspondingly. After the output signal is rectified by VD1, VD2 and filtered by C4, The index corresponding to relative humidity can be read directly from the voltmeter. The Rp potentiometer is used to zero the instrument.

Lithium chloride humidity sensitive resistor

The multi-chip resistance lithium chloride combined humidity sensor is a sensor that measures the humidity using the electrical characteristics (eg resistance value) of the humidity sensor and changes with the humidity. The humidity sensor is generally impregnated with moisture on the insulator. Or by making a layer of metals, semiconductors, polymer films, and powdered particles by evaporation, coating, etc., and in the process of moisture absorption and desorption of the moisture sensitive element, the ions H+ are decomposed by water molecules. The conduction state changes so that the resistance of the element changes with humidity.