Rosemount 755, Инструкция по эксплуатации

Страница: 51 / 94

4
O
PERATION
748183-H
4-1
Rosemount Analytical
December 1997
4.1 ROUTINE OPERATION
After the calibration procedure of Section 3.2, admit sample gas to the analyzer at the
same pressure and the same flow rates as used for the downscale and upscale gases.
The instrument will now continuously indicate the oxygen content of the sample gas.
If desired, the % RANGE Switch may be moved to a setting of lower sensitivity, i.e., of
wider span, than was used during calibration.
At this time an adjustment of instrument response time via R20 (Figure 3-1) may be
desirable to obtain the optimum compromise between response speed and noise.
4.2 EFFECT OF BAROMETRIC PRESSURE CHANGES ON
INSTRUMENT READOUT
If the analyzer exhaust port is vented through a suitable absolute back-pressure
regulator barometric pressure changes do not affect the percent oxygen readout.
However, if the analyzer exhaust port is vented directly to the atmosphere, any change
in barometric pressure after instrument standardization will result in a directly
proportional change in the indicated percentage of oxygen. This effect may be
compensated in various ways. If desired, correction may be made by the following
equation:
Where:
Pst = Operating pressure during standardization
Pan = Operating pressure during sample analysis
EXAMPLE (U.S. Units)
Pst = 760 mm Hg
Pan = 740 mm Hg
Indicated % O
2
= 40%
True % O
2
= 40% = 41.1% O
2