Simtronics GD1 MK3, Operating Manual

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GD1 Page 36 of 76 850-816926-EN R06
4
Verify the 4 – 20 mA output.
The output should change according to the
length of the Test Cell
multiplied with the gas
concentration. The table below contain some
typical values
Expected output value (ppm*m):
<length> * <concentration>
Note! Depending on the precision of the gas mix inside the Test Cell, do not expect to see
an exact 1:1 response compared to the test gas concentration.
Functional test finished!
Gas concentration
(ppm)
Expected response
Test Cell (length 0.54 m)
(ppm*m)
1
50 27
100 54
185 100 (50% full scale) 2
300 162
690 373 (out of default range)
1. The expected response on the GD1 can be calculated from the following formula:
Response_GD1 = length_test_cell (meters) * gas_concentration (ppm) + noise
where the noise normally varies at less than ± 8 ppm*m.
2. ** A test gas with approximate 50% full scale response is good practice.
3.4.1. Performing function test with CO
2
as a non-toxic alternative
As a non-toxic alternative to using H
2
S for the functional test, the GD1 is also set up to look
for a peak in the CO
2
wavelength. This response however, is only available using a Web
terminal through the service interface. The CO
2
measurement is not available on the 4-20
mA analogue output.