Theory of Operation 8
1100 Series FD Reference Manual 269
Detector Frontend Board (FLF)
Data Acquisition
The FLF board provides circuitry to measure three different physical effects:
• Fluorescence mode: peak value after flash
• Phosphorescence mode: integrated value after flash
• Chemoluminescence mode: amplified signal without flash operation
In parallel to the fluorescence signal the reference signal is acquired to get a
compensation of lamp drift and noise effects. Both signals are amplified and
buffered and routed to the ADC input multiplexer.
The 16-bit A/D-converter performs a conversion of the selected signal and
additionally of the corresponding reference signal and several other signals:
• monochromator positions
• board temperature
• leak sensor status
Then the digital data are polled by the FPGA on the FLM main board to be
available for calculations.
Flash Lamp Power Supply
The flash lamp is operated with discharge voltages of 500 V or 1250 V. The
electronics design provides the voltages using a regulating pulse width
modulator to switch a 24 V rail with a chopping frequency of 40 kHz to a
transformer. The resulting high voltage is rectified and fed back to the error
amplifiers which generate a control feedback signal for the regulator to
increase or decrease the duty cycle of the output signal. An additional
softstart-circuitry and a limitation of the maximum voltage ramp-up reduces
the resulting noise emission of the power supply. The complete flash voltage
supply is isolated by optocouplers to avoid crosstalk to other circuits by the
large switching currents.
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