What is a humidity sensitive resistor?

l  The characteristics

Humidity sensitive resistor is a kind of sensitive resistance element that changes with humidity and can be used as humidity measurement and condensation sensor. At present, there is no unified circuit symbol, some directly mark water molecules or H2O text, and some symbols are still represented by R.

There are many kinds of humidity sensitive resistors, which are divided into positive coefficient and negative coefficient according to the temperature change characteristic, and the resistance of positive coefficient resistor increases with the humidity, the negative coefficient is opposite. The commonly used negative coefficient humidity sensitive resistor.

The structure of the humidity sensitive resistor  is composed of a substrate ( insulating sheet ), a humidity sensing sheet and an electrode. When the moisture sensing material receives moisture, the resistance between the electrodes changes, completing the conversion of humidity to resistance change. The characteristics of the humidity sensitive resistor are : the resistance value changes with the increase of humidity by the exponential characteristic; a certain response time parameter, also known as the time constant, refers to the time needed to increase the resistance from zero to 63 % of the stability when the temperature is step, the characteristics of humidity response of the humidity sensitive resistor are characterized; other parameters include the humidity range, the stability of the resistance relative temperature change, etc.

l  Detect the humidity sensitive resistor.

 When detecting the humidity sensitive resistor, the nominal resistance of the humidity sensitive resistor should be measured under the dry condition, and it should be in accordance with the regulations. If the resistance is too small or too large or open, it was damaged.

Then add a certain humidity to the humidity sensitive resistor, the resistance should be changed.

Humidity sensitive resistor can not be repaired, emergency substitution can be used with the resistance of the carbon film resistor to scrape off the paint substitute ( remove the paint, affected by humidity, resistance changes ).

This article is from Allicdata Electronics Limited.