GasTech D-Guard2S Operator's Manual page 30

Connect the hose to the target gas cylinder regulator outlet.

Observe all safety procedures surrounding the use of the gas.
Turn on the gas and allow to run for about 60 seconds

Observe the detector response (target gas still running).

The display reading should be as per the gas concentration used for the test with a maximum

deviation of ±3.0ppm. The current loop signal response will depend on the concentration of the
target gas being used for the test.
The method for calculating the expected current loop reading is as follows:-
Read the gas concentration from the test gas cylinder (example 49.2 ppm)
Note the scale configuration of the detector under test (e.g. 0 - 100ppm. This is a 100ppm full scale detector).
Divide the test gas concentration by the detector full scale number (in this case 49.2 / 100 giving 0.492)
Multiply this number by 16 (in this case 0.492 x 16 giving 7.872)
Add 4 to the above result (in this case 7.872 + 4 giving 11.872)
The final result is the expected loop current in milliamps (11.872mA)
The observed reading on the test meter should be within ± 3.0% of the instruments scale (approx. ± 0.32mA)
If the readings from the detector are outside of the limits for either the purge gas or the target gas, a detector
calibration will be necessary. Please refer to the sections in this manual covering the operating system for
accessing the detector's calibration functions.
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D-Guard