Teledyne API T703 Calibrator Operation Manual Theory of Operation
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9.2.3.2. Heater Control

The relay PCA controls the DC heaters for the O3 generator and photometer lamp housing.
Figure 9-5: Heater Control Loop Block Diagram.

9.2.3.3. Relay PCA Status LEDs and Watch Dog Circuitry

Thirteen LEDs are located on the calibrator’s relay board to indicate the status of the calibrator’s heating zones
and some of its valves as well as a general operating watchdog indicator. Table 11-2 shows the states of these
LEDs and their respective functionality.
D15 (Yellow) - Photometer Lamp Heate
r
D16 (Yellow) – O3 Generator Lamp Heate
r
D7 (Green) Photometer Meas/Ref Valve
D6 (Green ) – Ext. Zero Air Valve
D9 (Green) – Photometer Pump Status
D1 (RED)
Watchdog
Indicator
Figure 9-6: Status LED Locations – Relay PCA
07223B DCN6378