Principles of Operation Teledyne API T703/T703U Calibrator Operation Manual

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Table 9-1: Relay Board Status LEDs

LED COLOR DESCRIPTION FUNCTION/INDICATION
D1 Red
Watchdog Circuit; I2C bus
operation. Blinks when I2C bus is operating properly
D2 Yellow Zero Air Pump (option) Status When lit the zero air AC pump is running.
D3-6 SPARE
D7 Green
Photometer Meas/Ref Valve
Status
When lit the valve open to the Measure
gas path; when not lit while instrument is
running, the valve is open to the
Reference gas path.
D8 Green Zero Air Shutoff Valve (option) Status When lit, ZA shutoff valve open.
D9 Green O3 Pump Status When lit, O3 pump running
D10 Green T703U Divert Valve Status when lit, divert valve open.
D11 Green T703U O3 Generator Valve Status When lit, O3 generator valve open.
D12 - 14 SPARE
D15 Green Photometer Lamp Heater Status When lit the photometer UV lamp heater
is on
D16 Green O3 Generator Lamp Heater When lit the O3 generator UV lamp heater
is on

9.2.3.4. Relay PCA Watchdog Indicator (D1)

The most important of the status LEDs on the relay board is the red I2C Bus watchdog

LED. It is controlled directly by the calibrator’s CPU over the I2C 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 I2C bus has stopped functioning) this Watchdog

Circuit automatically shuts all valves and turns off all heaters and lamps.

07223C DCN6572