50 | IPS-4 Zone1/Analyzer
Adjusting the Zero/Span Fluid Flow Rate
When the zero or span (if used) flow solenoid is in an energized state,
Instrument Air (or Nitrogen or distilled water) flows into the sample path
via a solenoid manifold block and a flow meter. The flow rate of Zero/
Span (if used) fluid must be high enough to adequately flush the Measur-
ing Cell of sample fluid to obtain a “good zero.”
Typically, the IPS-4 Analyzer controls the zero (and span, if used)
flow rate; no adjustments are required.
If the customer provides the sample system zero, run the manual zero
at a flow rate of 2.5 L/minute (0.08 scfm). Since excess air flow into
the analyzer sample system will cool the Measuring Cell and Oven/
Sample System Enclosure, the optimum Zero fluid flow rate is the
lowest consistent with a good zero.
A good zero can be defined as a state where the concentration outputs
are stable and further increases in Zero fluid flow rate do not reduce the
concentrations observed on the analyzer User Interface Panel. A mid-scale
flow indicator (or meter) should be sufficient for this purpose.
While the sample system is warming up, or when the analyzer is in
standby mode (Not Ready state), zero flow may be desired. During these
conditions, it is important that the sample system is kept free of contami-
nation by the sample fluid.
For additional information, refer to the Sample System Manual Supplement
in the “Supplemental Information” tab of this manual or in the Documen-
tation Package shipped with the analyzer.
Adjusting the Sample Flow Rate
Applications With an Aspirator:
The Aspirator Pressure Regulator is used to control the sample flow
through the system. A typical sample flow rate is in the range of
3.0–5.0 L/minute (0.1–0.2 scfm) and can be achieved by adjusting the Aspi-
rator Pressure higher than 70 kPa (10 psi) above the sample stream pres-
sure. View the flow indicator (or meter), if used.
To avoid damaging the pressure transducer, do not set the pressure
higher than 105 kPag (15 psig).
The analyzer pressure – measured by the pressure transducer – can also
be used to set the sample flow rate. This is accomplished by first measur-
ing the sample stream pressure with no aspiration (Drive Air Isolation
NOTE
NOTE
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