Detector - Teledyne UA-6 Installation And Operation Manual

UA-6 Detector
Section 4 Theory of Operation
4.1.2 UA-6 Detector
Figure 4-2 UA-6 Detector Block Diagram
4-2
The detector, presented as a block diagram in Figure 4-2, receives
two current signals from the optical unit. These two signals are
subtracted from one another. In general, one signal is generated
by a reference liquid, most likely a non-sample injected buffer. If
both light paths are buffered with the same substance, any
unwanted signal interference generated by the liquid, e.g. tem-
perature drift, optical density or refraction changes are reduced
by this subtraction process thus making the system more stable.
The difference signal is converted to a logarithmic function. The
chart recorder output is the logarithm of the light intensity. Next,
the signal is amplified and filtered as necessary. At this point it is
sent to the peak separation network and chart recorder. With the
help of any external signals that may be present, like event
marks from a fraction collector or injection marks from an auto-
matic injection valve, a trace is made on the recorder chart paper.
The necessary control signals for indexing a fraction collector are
also generated.