ST650EX / ST650-CO
2
/ ST350EX
v3.16
23
4.1.1 Calibration Zero level detector (ZERO calibration)
Zero calibration ST350EX (ppm version)
Always use a water bottle during calibration of a ST350EX. The gas should flow
above the water surface and not flow through the water.
During calibration of the zero level, no background gas should be present. When in doubt use
synthetic air for calibration of the zero level.
Zero level without synthetic air:
Adjust the zero level using the ZERO potentiometer to 4mA.
Zero level with synthetic air:
Insert a water bottle in the gas flow between the gas cylinder and the flow adapter.
Connect the flow adapter to the sensor.
Open the valve of the gas cylinder.
Apply synthetic air with a flow of 30l/h.
Wait until the sensor signal has stabilised.
Adjust the zero level using the ZERO potentiometer to 4mA.
Zero level ST650EX (IR / LEL version)
When performing a zero level calibration no background gas concentration should be present.
Use synthetic air when in doubt.
Zero level without synthetic air:
Adjust the zero level using the ZERO potentiometer to 4mA.
Zero level with synthetic air:
Connect the flow adapter to the sensor
Open the valve of the gas cylinder
Apply synthetic air with a flow of 20-30l/h
Wait until the sensor signal has stabilised
Adjust the zero level using the ZERO potentiometer to 4mA