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Principles of Operation Teledyne API – Model T700 Dynamic Dilution Calibrator
284
10.3.3. RELAY PCA
The relay PCA is one of the central switching and power distribution units of the
calibrator. It contains power relays, valve drivers and status LEDs for all heated zones
and valves, as well as thermocouple amplifiers, power distribution connectors and the
two switching power supplies of the calibrator. The relay PCA communicates with the
motherboard over the I
2
C bus and can be used for detailed trouble-shooting of power
problems and valve or heater functionality.
Generally, the relay PCA is located in the right-rear quadrant of the calibrator and is
mounted vertically on the back of the same bracket as the instrument’s DC power
supplies, however the exact location of the relay PCA may differ from model to model
(see Figure 3-5 or Figure 3-6).
Power
Connections
for DC
Heaters
Status LED’s
(D2 through D16)
DC Power Supply
Test Points
Watchdog
Status LED (D1)
I
2
C Connector
DC
Valve Control
Drivers
AC Power
IN
DC Power
Distribution
Connectors
V
alve Option
Control
Connector
Figure 10-5: Relay PCA
This is the base version of the Relay PCA. It does not include the AC relays and is used
in instruments where there are no AC powered components requiring control. A plastic
insulating safety shield covers the empty AC Relay sockets.
06873B DCN6388