Galvanic Applied Sciences 943-TGS-CE, Operation Manual

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Revision 5 55 August 2021
When a zero calibration cycle is triggered, the zero calibration sequence proceeds in the
following order:
1. The Mode relay output state changes to Calibrate (yellow) and the Control relay output
changes to Manual (yellow)
2. Any analog outputs configured for Hold behaviour will hold the last value they were
outputting prior to the zero calibration cycle being initiated.
3. The Zero / Sample solenoid switches off, allowing zero gas to purge the analyzer’s
sample handling system, including the measurement cell, as well as the sample probe.
This purge continues for the duration specified by the Zero Purge Interval parameter
(refer to Section 4.8).
4. Once the zero purge time has elapsed, the computer collects 10 spectrometer scans
on zero gas and averages them together to calculate a new zero baseline.
5. The Zero / Sample solenoid switches on, allowing sample gas to be drawn back up the
probe and into the analyzer sample handling system and measurement cell by the
aspirator.
6. During this period, any analog outputs configured for Hold behaviour will continue to
hold the last value output prior to the initiation of the calibration cycle The analyzer
waits for the number of seconds specified by the Zero Hold Interval parameter of the
configuration data (Section 4.8.4) to allow the calculated concentration values to
stabilize at on-line values before updating the analog outputs.
7. If no pre-existing fault conditions are present, the Mode relay output changes to Run
(green) and the Control relay output changes to Auto once the Zero Hold Interval time
has elapsed.
4.3.5 Back Purge Indicator and Control
The fail-safe condition of the analyzer is to have instrument air flowing through the
measurement cell, the analyzer sample handling system, and the sample probe. This is a
condition known as back purge. The Back Purge indicator and manual controls are shown
in Figure 27.
Figure 27: Back Purge Indicator and Manual Controls
The back purge indicator shows the current back purge status. If it is green, this indicates
that the analyzer is currently drawing sample into the measurement cell. If it is red, this
indicates that the analyzer is currently in back purge, either due to the analyzer being
manually placed into back purge OR due to a fault condition causing an automatic back
purge OR because the analyzer is currently carrying out a zero calibration cycle.