Chapter 8 Theory of Operation
Flow Components
The Model 48C operates at normal atmospheric pressure. Figure 1-1 summarizes the
flow schematic. A downstream pump and capillary control the sample flow through the
optical bench, which is monitored by a flow sensor. The nominal flow is 1 liter per
minute, with values between 1/2 - 2 liters per minute acceptable.
The optional zero/span and sample valves are operated by successive engagements of the
RUN pushbutton on the front panel. The control signals for the valves go through the
microcomputer.
Temperature and Pressure Transducer
Temperature and pressure must be measured if one wants to compensate for changes in
ambient values. The pressure is measured by a pressure transducer. The temperature is
measured by a thermistor.
8-6
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