System Description
Firmware
Thermo Fisher Scientific
Model 48
i
Instruction Manual
8-3
The optical pickup detects the position of the gas filter wheel, provides
synchronizing signals for the signal demodulation, and provides a method
for checking the chopper motor speed.
The gas filter wheel contains samples of CO and N
2
gas that filter the
radiation from the infrared source. A chopper disk that rotates along with
the wheel periodically interrupts the radiation to create a modulated signal.
The infrared source is a special wire-wound resistor operated at high
temperature to create infrared radiation.
The pre-amplifier assembly is mounted on the optical bench along with an
infrared detector that detects the energy of the infrared light passing
through the optical bench. It amplifies the pulsating signal from the
infrared detector.
The sample flow sensor, located at the optical bench outlet, measures the
flow of sample through the optical bench.
The pressure transducer measures the pressure of the sample gas.
The capillary and the pump control the sample gas flow.
The pump draws the sample gas through the optical filter bench.
The purge flow switch monitors the flow of purge gas when the filter wheel
purge gas option is installed.
The processor firmware tasks are organized into four areas:
●
Instrument control
●
Monitoring signals
●
Measurement calculations
●
Output communication
Optical Pickup
Gas Filter Wheel
Infrared Source
Pre-amplifier Assembly
with IR Detector
Sample Flow Sensor
Pressure Transducer
Capillary
Pump
Purge Flow Switch
(optional)
Firmware
