TELEDYNE API
M703E Calibrator Operator’s Manual Theory of Operation

9.2.3.1. Valve Control

The relay board also hosts two valve driver IC's, each of which can drive up four valves. In the M703E, the relay
PCA controls only those valves associated with the O3 generator and photometer options.

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 & 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

05744 Rev B 141