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Theory of Operation Model GFC7001E Carbon Dioxide Analyzer
Teledyne Analytical Instruments 246
11.5.5.5. Status LED’s
Eight LED’s are located on the analyzer’s relay board to show the current status on the various control functions
performed by the relay board. They are listed on Table 11-4.
Table 11-4: Relay Board Status LED’s
LED COLOR FUNCTION STATUS WHEN LIT STATUS WHEN UNLIT
D1 RED Watch Dog Circuit
Cycles On/Off Every 3 Seconds under direct control of the
analyzer’s CPU.
D2 YELLOW Wheel Heater HEATING NOT HEATING
D3 YELLOW Bench Heater HEATING NOT HEATING
D4 YELLOW Spare N/A N/A
D5 GREEN
Sample/Cal Gas
Valve Option
Valve Open to CAL GAS
FLOW
Valve Open to SAMPLE Gas Flow
D6 GREEN
Zero/Span Gas
Valve Option
Valve Open to SPAN GAS
FLOW
Valve Open to ZERO GAS FLOW
D7 GREEN
Shutoff Valve
Option
Valve Open to CAL GAS
FLOW
Valve CLOSED to CAL GAS
FLOW
D8 GREEN IR SOURCE Source ON Source OFF
STATUS LED’s
DC VOLTAGE TEST
POINTS
RELAY PCA
PN 04135
Figure 11-14: Location of relay board Status LED’s
11.5.5.6. I
2
C Watch Dog Circuitry
Special circuitry on the relay board monitors the activity on the I
2
C bus and drives LED D1. Should this LED
ever stay ON or OFF for 30 seconds, the watch dog circuit will automatically shut off all valves as well as turn off
the IR Source and all heaters. The GFC Wheel motor will still be running as will the Sample Pump, which is not
controlled by the relay board.