GE UV-1 - Manual (Page 6)

2. General Description
Fig. 2 Block diagram
The photocurrent from each detector is amplified in a pre-amplifier
before passing to the signal processing circuitry in the control unit.
If transmission is to be monitored, the signal passes directly to the
low pass filter. If AU is to be monitored, the reference cell light
intensity (IR) is compared with the sample cell intensity (IS) to form
log (IR/IS) in a logarithmic circuit before passing to the low-pass filter.
The signal finally passes to the range selector before being presented
to the output terminal.
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