Thermo Scientific 43iQ, Instruction Manual

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System Description
Optical Bench DMC
Thermo Scientific 43iQ Instruction Manual 8-3
The flash lamp trigger assembly pulses the UV flash lamp at a rate of 10
times per second for improved signal-to-noise ratio and long term stability.
The lamp is operated in the pulsed mode for six major reasons:
●
Long life
●
High optical intensity – improved signal to noise ratio
●
Small size
●
Low power requirements – less than 1 watt
●
Long-term stability
●
Chopped signal processing – no dark current drift
The flash lamp provides the ultraviolet light source that causes the
fluorescence reaction in the SO
2
molecules.
The flash trigger board is located in the base of the flash lamp assembly. It
receives high voltage and the trigger signal from the measurement interface
board and uses a small transformer to produce a short, high-voltage pulse to
fire the flash lamp.
The flash intensity assembly is located in the fluorescence chamber and
continuously monitors the pulsating UV flash lamp. This photodetector is
connected to a circuit that automatically compensates for fluctuations in
flash lamp output.
The PMT power supply produces high voltage to operate the
photomultiplier tube used in the measurement system. The output voltage
is adjustable from approximately 600 to 1200 volts under software control.
The PMT converts optical energy from the reaction to an electrical signal.
This signal is sent to the input board which transmits it to the processor.
The optical bench DMC 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
2
channel.
Flash Lamp Trigger
Assembly
Flash Lamp
Flash Trigger Board
Flash Intensity Assembly
Photomultiplier
Tube
Optical Bench DMC
Board