Trace Oxygen (O2) and Humidity Sensor TOS 3.0a

Sensor control and display unit (SKE) with selector switch for O2 and H2O

Additional function of the TOS 3.0 sensor for additional measurement of humidity

In the standard configuration, the trace oxygen sensor TOS 3.0 does not react to oxygen molecules other than O2, especially water. The applied voltage is kept low enough to avoid electrochemical degradation. In this way, the sensor reacts selectively to free oxygen.

In a special configuration, the sensor is equipped with a switch to provide a higher voltage to decompose water vapor. This creates free oxygen, which is measured and displayed in addition to the existing unbound oxygen.

The amount of water vapor results from the difference between the measured values for the switch positions O2 .5H2O and O2. Since the values shown indicate O2 concentrations, the difference must be multiplied by 2 to obtain the water vapor concentration:

PH2O = 2 ( [displayed value in switch position O2 .5H2O] - [displayed value in switch position O2] )

After switching, the time to build up the new continuous current is typically a few minutes. This time should be planned for the measurement.