Galvanic Applied Sciences 943-TGX, Operation Manual

Page: 34 / 110

Revision 4 34 August 02, 2019
4.3.4 Manual Zero
The Manual Zero button starts the zero calibration sequence of the analyzer which
incorporates the checking and adjusting of the instrument zero (baseline). No span correction
is required under normal circumstances on an installed analyzer. The calibration sequence is
identical whether triggered manually or automatically.
When triggered, the calibration sequence proceeds in the following order:
a) The
Mode
relay output changes to
Calibrate
and the
Control
relay output changes to
Manual.
b) Zero gas is introduced into the measurement cell and is allowed to purge the
measurement cell for the number of seconds specified by the
Zero Purge Interval
configuration parameter (Section 4.8).
c) At the conclusion of the
Zero Purge Interval
, the computer averages the last ten (10)
spectrometer scans and determines a new reference scan vector (captures the new zero
value).
d) The analyzer waits for the number of seconds specified by the
Zero Hold Interval
parameter of the configuration data (Section 4.8.4)
e) During this period, process sample gas is drawn into the measurement cell and the
displayed concentration values will rise from zero to the measured values. The
Zero Hold
Interval
allows the analyzer concentration outputs to stabilize at on-line values before the
controller updates the outputs.
f)
The Mode
relay output changes to
Run
and
Control
relay outputs changes to
Auto
at the
expiration of the
Zero Hold Interval
(barring a pre-existing fault condition).
4.3.5 Back Purge
The default condition of the analyzer is to have instrument air flowing through the sample cell.
When
Back Purge
is selected, the analyzer sampling system is continuously back purged
with zero gas. This is useful as a precursor to maintenance activities or when long term
purging is required.
4.3.6 Graphic Display
The
Graphic
display of the air demand is updated once per second. The time and intensity
scales can be set on the
Config
panel (Section 4.8).