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Theory of Operation Teledyne API - Model 200EH/EM Operation Manual
218
10.4.8. STATUS LEDS & WATCH DOG CIRCUITRY
Thirteen LEDs are located on the analyzer’s relay board to indicate the status of the analyzer’s heating zones
and valves as well as a general operating watchdog indicator. Table 11-2 shows the states of these LEDs and
their respective functionality.
D3 (Yellow) – NO
2
Converter Heate
r
D4 (Yellow) – Manifold Heate
r
D2 (Yellow) – Reaction Cell Heate
r
D5(Yellow)
D6 (Yellow) – O
2
Sensor Heate
r
D7 (Green) – Zero / Span Val
v
D8 (Green) – Sample / Cal
D9 (Green ) – Auto /
Z
D10 (Green) – NO
x
D1 (RED)
Watchdog
Indicator
Figure 10-10-24: Status LED Locations – Relay PCA
10.4.8.1. Watchdog Indicator (D1)
The most important of the status LED’s on the relay board is the red I
1
C Bus watch-dog LED. It is controlled
directly analyzer’s CPU over the I
2
C bus. Special circuitry on the relay PCA watches the status of D1. Should
this LED ever stay ON or OFF for 30 seconds, indicating that the CPU or I
2
C bus has stopped functioning, this
Watchdog Circuit automatically shuts all valves and turn off all heaters and lamps.
04521C (DCN5731)