OPERATING MANUAL OXYGEN MONITORING SYSTEM
OMS 420
28
9.7
Calibration
The transmitter should be powered up for at least 2 … 3 hours before calibration.
A test (calibration) gas cylinder is connected to the calibration gas inlet port for calibration.
Adjustment can be done manually or automatically using the solenoid valves of the optional pneumatic unit PU420.
The test gas (clean fresh air/instrument air or calibration gas) flows through the hole inside the small flange (sensor mani-
fold), purges the sensors and exits through the filter screen to the inside probe tube mounted on the stack.
On site calibration is done without removing the probe from the stack.
After calibration, tighten the calibration inlet port plug with a 14 mm wrench for 1/6 of a turn.
Perform adjustment:
1
Purge sensor with ambient air (40 l/h using the calibration gas inlet port).
2
When being purged with fresh air, the analog output signal should be 17.37 mA (for 0 – 25 % O
2
measuring range).
3
With calibration gas (2% O
2
in N
2
), the analog output should be 5.28mA (for 0 - 25% O
2
measuring range).
4
The transmitter is now ready for operation.
Use calibration gas cylinder at least every 3 - 6 months.
Calibration with ambient clean air can be done automatically on a daily basis using the pneumatic option PU420.
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