FIXED POINT RH EQUILIBRIUM OF GAS SENSOR TEST CHAMBER USING SIMPLE AIR BUBBLER METHOD

Relative Humidity (RH) is considered as one of the important variable to be controlled during testing and characterizing of metal oxide gas sensor. This is because the metal oxide can easily react with the hydrogen and oxygen molecule of the water vapor which associated with RH level. In this paper, the effect of using nitrogen as carrier to feed the analyte to the sensor inside a 40 liter capacity container has been studied. When Nitrogen gas was supplied to the chamber, the RH value dropped significantly from initial ~67 % RH to ~7 % RH within one hour duration. As an alternative, a simple bubbler system was introduced to minimize the drop of RH. The bubbler which was filled with 100% distilled water or mixed with a certain percentage of glycerol are able to maintain the RH to a certain level for a certain period of time.