Model B12-69 Wet Oxidant Gas Transmitter
O & M Manual
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Rev-G, 7/15
OPERATION
After mechanical and electrical installation is complete, the system is ready for operation. Prior
to start-up, recheck the loop wiring and sensor connections to be sure everything is correct. Reversing
the loop wiring will not damage the transmitter, but other devices in the loop may be adversely affected.
As soon as DC loop power is applied, the transmitter will begin to operate, transmitting a 4-20
mA signal proportional to gas concentration. When first energized, the sensor will spike to a high value
and then slowly begin to recover toward zero. This is normal and the system must be allowed to stabilize
for at least a few hours before making any adjustments. The sensor must be connected to the transmitter
and the transmitter must be powered for the sensor to stabilize.
TRANSMITTER TEST POINTS
In order to read the transmitter output locally, a digital volt (DVM) meter is recommended for
transmitters without displays. The transmitter circuit board contains test points marked TP1 (see Figure
6) that allow an operator to read the 4-20 mA output without breaking the loop wiring. The test points are
across a precision 10 ohm resistor that is part of the current output circuit. Therefore, any changes at the
test point are a direct indication of changes in the output signal. The test point voltage will be 40 - 200
mv. proportional to 4-20 mA. This test point is used for zero and calibration functions.
