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T400 Ozone Analyzer Operator’s Manual Theory of Operation
291
13.3.4.3. Valve Control
The valve that switches the gas stream to and from the analyzer’s O
3
scrubber during the
measure/reference cycle (see Section 13.1.3) is operated by an electronic switch located
on the relay
PCA. This switch, under CPU control, supplies the +12VDC needed to
activate each valve’s solenoid.
Similar valves also controlled by the relay PCA are included in the following optional
components:
On instruments with the ZERO/SPAN valve option (OPT- 50A) there are two
additional valves:
The ZERO/SPAN valve selects which calibration gas inlet (the ZERO gas inlet
or the SPAN Gas Inlet) is the source of gas when the analyzer is in one of its
calibration modes (see Figure 3-22).
The SAMPL
E
/CAL valve selects either the sample inlet when the analyzer is in
SAMPLE mode or the calibration gas stream when the analyzer is in one of its
calibration modes (see Figure 3-22).
On inst
ruments with the IZS valve option (OPT- 50G) one additional valves (the
SAMPLE/CAL valve) selects either the sample inlet when the analyzer is in
SAMPLE mode or the dry air inlet when the analyzer is in one of its calibration
modes (see Figure 3-17).
13.3.4.4. Heater Control
In the base version of the Model T400 photometric analyzer, there is only one DC heater
operated by the relay PCA. It is attached to the Photometer UV Lamp housing and
maintains the temperature of the UV Lamp at a constant 58ºC.
Additional DC heater also controlled by the relay PCA, are included in the following
optional components:
On instruments with Zero/Span valve option (OPT-50A) the metal wool scrubber
option (OPT- 68) there is a DC heater embedded in the scrubber maintains it at a
constant 110ºC.
On instruments with the IZS valve option (OPT- 50G) there is a DC heater attached
to the IZS O
3
generator UV Lamp that maintains it at a constant 48ºC
06870C DCN6332