Ethanol Sensor Calibration Procedure
Theory of Operation
The probe of PS-2194 Ethanol Sensor consists of Pt-W electrodes printed on a multi-crystaline alumina (Al2O3) subtrate with an integrated RuO2 heater.
When a metal oxide such as alumina is heated to a sufficiently high temperature while exposed to air, oxygen from the air is absorbed on the surface of the metal oxide, transferring negative charge to the oxygen and leaving a positively charge surface barrier to electron flow at each grain boundary in the metal oxide.
Many solvent vapors (such as ethanol) act as reducing agents for this absorbed oxygen, decreasing the charge barriers and making it easier for electrons to flow past the grain boundaries. The conductivity of the metal oxide is related to the concentration and chemical composition of the reducing gas by
R = R0 (C)−α
Any of the following solvent vapors will significantly reduce the metal oxide:
In addition, the sensor should be expected to be sensitive to chemically related solvent vapors.
The resistance of the aluminum oxide is converted to an output voltage by means of a voltage divider.
Calibration (for Ethanol measurements)
Calibration data is retained in non-volatile memory in the sensor, but daily calibration is recommended for best results.
The sensor should be stored in a sealed polyethylene bag with clean air at ambient humidity. Do not use silica gel or store in any bag with a perceptible odor, such as a bag made of PVC, which can off-gas phtalates.
Creation Date: 03/30/2010