Series A12
Unisens
2-Wire Transmitter
O & M Manual
- 22 -
Rev-L, 7/15
SENSING MODULE ZERO ADJUSTMENT
As previously mentioned, adjusting the sensing module zero requires that the sensor be exposed
to air that is free of the target gas or any other gases that might cause either negative or positive
interference to that sensor. Refer to the section of this manual related to the specific gas type for
information on potential interferences.
If the area in which the sensor is operating is know to be gas free, then the sensing module can
be zeroed without further equipment. If not, use of "zero air" from a gas cylinder is recommended. Zero
air is available as part of all ATI calibration kits, or may be obtained from any specialty gas supplier.
When zero air is to be used, a calibration adapter (part no. 00-0248) must be used. The calibration
adapter provides a confined space around the sensor into which the zero air can flow. There are two
calibration adapters available for A12 sensor modules. For D10 modules without Auto-Test, the adapter
slips inside the splash guard for the sensor module. For D28 modules with Auto-Test generator, the
adapter slides on to the generator.
Note: The gas inlet port (1/8” barb fitting) on the adapter used for the D28 module must be unscrewed
partially to allow the adapter to slide over the generator. When in place, screw the fitting in so
that it is retained in the slot between the generator and sensor.
Figure 11 - Sensor Calibration Adapter Assemblies
