Galvanic Applied Sciences 943-TGX, Operation Manual

Page: 27 / 110

Revision 4 27 August 02, 2019
3.3 Analyzer Outputs
The 943-TGX analyzer generates both analog and digital output signals for connection to the
users’ plant control system. The analog signals include the calculated Air Demand, and the
measured concentrations of H
2
S, SO
2
, and optionally a user selectable signal for analog
output 4. The provided digital signals (relay contacts) represent indications of the current
analyzer and enclosure purge state.
3.3.1 Analog Outputs
The
analog outputs
are ranged in software, based on information provided specifically for a
particular plant. Four loop powered 4 – 20 mA outputs are available:
•
Analog Output 1: Air Demand
•
Analog Output 2: H
2
S Concentration
• Analog Output 3: SO
2
Concentration
•
Analog Output 4: User Selectable from Air Demand, H
2
S, SO
2
, Sigma S (the sum of H
2
S
and SO
2
concentrations), CS
2
or H
2
S/SO
2
ratio.
Analog outputs
for H
2
S and SO
2
concentrations can be programmed to be either Track or
Hold. If the output is programmed to be ‘Track’, the output will track the calculated values
displayed on the Front Panel of the computer. (Tracking outputs will follow the zero
calibration sequence as it occurs.) If the output is programmed to be ‘Hold’, the output will
track the calculated value displayed on the Front Panel until an abnormal condition, zero
calibration or fault condition exists. The output will then be held until normal operation is re-
established.
The Air Demand analog output is Hold only. When the analyzer is in normal operation, the
Air Demand analog output tracks the displayed value.. When an abnormal condition, zero
calibration or fault condition exists, the analyzer automatically holds the last valid Air Demand
output value until normal operation is re-established.
The analog outputs are updated at a rate of once per second, driven by the calculation cycle
frequency.