Teledyne 9110EH - Nitrogen Oxides Analyzer - Manual (Page 199)

Model 9110EH Instruction Manual Theory of Operation
The output labeled A4 can be set by the user (Section 6.7.2) to carry the signal of any of
these TEST parameters: none , PMT DETECTOR, OZONE FLOW, SAMPLE FLOW,
SAMPLE PRESSURE, RCELL PRESSURE, RCELL TEMP, MANIFOLD TEMP, IZS TEMP,
CONV TEMP, PMT TEMP, BOX TEMP, HVPS VOLTAGE.
In its standard configuration, the analyzer comes with all four of these channels set up to
report a DC voltage (default A4 signal is NONE). However, current loop drivers can be
purchased for the first three of these outputs, A1 to A3 (Section 5.3. for this optional
equipment, Section 6.7.3.5 for setup).
All of the analog outputs are connected back to the A/D converter through a loop-back
circuit, which permits the voltage outputs to be calibrated by the CPU without the need for
any additional tools or fixtures (Section 6.7.3).
10.3.5.5. External Digital I/O
The external digital I/O performs two functions.
The STATUS outputs carry logic-level (5V) signals through an optically isolated 8-pin
connector on the rear panel of the analyzer. These outputs convey on/off information about
certain analyzer conditions such as CONC VALID. They can be used to interface with
certain types of programmable devices (Section 6.9.1).
The CONTROL inputs can be initiated by applying 5V DC power from an external source
such as a PLC or data logger (Section 6.9.2). Zero and span calibrations can be initiated by
contact closures on the rear panel.
10.3.5.6. I 2 C Data Bus
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 are then fed to the keyboard/display interface
and finally onto the relay board.
Interface circuits on the keyboard/display interface and relay board convert the I 2 C data to
parallel inputs and outputs. An additional interrupt line from the keyboard to the mother-
board allows the CPU to recognize and service key strokes on the keyboard.
10.3.5.7. Power-up Circuit
This circuit monitors the +5V power supply during analyzer 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.
10.3.6. Power Supply/ Circuit Breaker
The analyzer operates in two main AC power ranges: 100-120 VAC and 220-240 VAC (both
± 10%) between 47 and 63 Hz. Note, however, that the analyzer’s pump is specifically
configured for one voltage and one frequency only. Individual analyzers are set up at the
factory to accept one of these two voltage ranges. As illustrated in Figure 10-16, 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
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