Teledyne GFC7000E User Manual Page 184

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Model GFC7000E Instruction Manual THEORY OF OPERATION
04584 Rev A1 173
10.3.6.6. External Digital I/O
This External Digital I/O performs two functions.
Status Outputs
Logic-Level voltages are output through an optically isolated 8-pin connector located on the rear
panel of the analyzer. These outputs convey good/bad and on/off information about certain
analyzer conditions. They can be used to interface with certain types of programmable devices
(see Section 6.13.1.1).
Control Inputs
By applying +5VDC power supplied from an external source such as a PLC or Datalogger (see
Section 6.13.1.2), Zero and Span calibrations can be initiated by contact closures on the rear
panel.
10.3.7. I
2
C Data Bus
An I
2
C data bus is used to communicate data and commands between the cpu and the
keyboard/display interface and the relay board. I
2
C is a two-wire, clocked, digital serial i/o bus
that is used widely in commercial and consumer electronic systems. A transceiver on the
motherboard converts data and control signals from the PC-104 bus to I
2
C. The data is then fed
to the keyboard/display interface and finally onto the relay board.
Interface circuits on the keyboard/display interface and relay boards convert the i
2
c data to
parallel inputs and outputs. An additional, interrupt line from the keyboard to the motherboard
allows the CPU to recognize and service key presses on the keyboard.
Power up Circuit
This circuit monitors the +5V power supply during start-up and sets the Analog outputs, external
digital I/O ports, and I
2
C circuitry to specific values until the CPU boots and the instrument
software can establish control.
10.3.8. Power Supply/ Circuit Breaker
The analyzer operates on 100 VAC, 115 VAC or 230 VAC power at either 50Hz or 60Hz. Individual
units are set up at the factory to accept any combination of these five attributes. As illustrated in
Figure 10-15, power enters the analyzer through a standard IEC 320 power receptacle located on
the rear panel of the instrument. From there it is routed through the On/Off switch located in the
lower right corner of the Front Panel. A 6.75 Amp circuit breaker is built into the ON/OFF Switch.
AC power is distributed directly to the sample gas pump. The bench and GFC wheel heaters as
well as the GFC wheel receive AC power via the relay board.
AC Line power is converted stepped down and converted to DC power by two DC power supplies.
One supplies +12 VDC, for valves and the IR source, while a second supply provides +5 VDC and
±15 VDC for logic and analog circuitry. All DC voltages are distributed via the relay board.
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