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System Description
Electronics
Pressure Sensor
Bench Heater
PMT Power Supply
Diagnostic LED
Input Board
Digital Output Board
Front Panel
Connector Board
8-8
Model 43i Trace Level-Enhanced Instruction Manual
The pressure sensor assembly consists of a board containing an
instrumentation amplifier and a pressure transducer with a gas input
Assembly
fitting. The pressure transducer output is produced by measuring the
pressure difference between the sample gas pressure and ambient air
pressure.
The fluorescence chamber temperature is measured with a thermistor. The
voltage across the thermistor is fed to the main processor for use in
calculating and displaying the reaction chamber temperature. The voltage
across the thermistor is also compared to a set-point voltage and used to
control that the reaction chamber heaters to maintain a constant
temperature.
The PMT power supply produces high voltage to operate the
photomultiplier tube used in the measurement system. The output voltage
Assembly
is adjustable from approximately 600 to 1200 volts under software control.
The diagnostic LED is used to provide an alternate light source to the
PMT to determine if the PMT is operating when the operating condition
of the flash lamp is unknown.
The input board accepts the current signal from the PMT and converts it
to a voltage, which is scaled by a factor of approximately 1, 10, or 100
depending on the full-scale range of the SO
signal is converted to a frequency and sent to the microprocessor.
The digital output board connects to the motherboard and provides
solenoid driver outputs and relay contact outputs to a connector located on
the rear panel of the instrument. Ten relay contacts normally open (with
power off) are provided which are electrically isolated from each other.
Eight solenoid driver outputs (open collector) are provided along with a
corresponding +24VDC supply pin on the connector.
The front panel connector board interfaces between the motherboard and
the front panel mounted function key panel and Graphics display. It serves
as central location to tie the three connectors required for the function key
panel, the graphics display control lines, and the graphics display backlight
to a single ribbon cable extending back to the motherboard. This board
channel. The scaled voltage
2
Thermo Fisher Scientific
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Troubleshooting
