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Teledyne API M100E Analyzer Operation Manual Optional Hardware and Software
59
Manually from the analyzer’s front panel by using the SIGNAL I/O controls located under the DIAG Menu
(refer to Section 6.9.2),
By activating the instrument’s AutoCal feature (refer to Section 8.8),
Remotely by usin
g the external digital control inputs (refer to Section 7.3.1.2 and Section 8.7.1), or
Remotely through the
RS-232/485 serial I/O ports (refer to Appendix A-6 for the appropriate commands).
EXTERNAL ZERO AIR SCRUBBER
The IZS option includes an external zero air scrubber assembly that removes all SO
2
the zero air source. The
scrubber is filled with activated charcoal.
SPAN GAS SOURCE
Span gas is created when zero air passes over a permeation tube containing liquid SO
2
under high pressure,
which slowly permeates through a PTFE membrane into the surrounding air. The speed at which the SO
2
permeates the membrane is called the effusion rate. The concentration of the span gas is determined by three
factors:
Size of the membrane: The larger the area of the membrane, the more permeation occurs.
Temperature of the SO
2
: Increasing the temperature of the increases the pressure inside the tube and
therefore increases the effusion rate.
Flow rate of the zero air: If the previous two variables are constant, the permeation rate of air into the zero
air stream will be constant. Therefore, a lower flow rate of zero air produces higher concentrations of SO
2
.
The M100E usually has a constant flow rate and a constant permeation rate; hence, variations in
concentration can be achieved by changing the IZS temperature.
NOTE
The permeation tube is not included in the IZS Option and must be ordered separately.
Refer to Section 5.7.3.
PERMEATION TUBE HEATER
In order to keep the permeation rate constant, the IZS enclosure is heated to a constant 50° C (10° above the
maximum operating temperature of the instrument). The IZS heater is controlled by a precise PID
(Proportional/Integral/Derivative) temperature control loop. A thermistor measures the actual temperature and
reports it to the CPU for control feedback.
CAUTION
Gas flow though the analyzer must be maintained at all time for units with a permeation tube installed.
Insufficient gas flow allows gas to build up to levels that will contaminate the instrument.
5.7.3. IZS PERMEATION TUBES OPTIONS FOR SO
2
Several replacement permeation tubes are available for the IZS option. They are identical in size and shape but
are designed to have different effusion rates.
04515F DCN6048