Instruction Manual

245364-V May 2002

Model 755A

 

3-8 EFFECT OF BAROMETRIC PRESSURE

3-7 ROUTINE OPERATION

CHANGES ON INSTRUMENT READOUT

After the calibration procedure of Section 3-4 (page 3-4), admit sample gas to the analyzer at the same pressure and the same flow rates used for the zero and span gases. The instrument will now continuously indicate the oxygen content of the sample gas.

At this time, an adjustment of electronic response time (R30 on the Control Board, see Table 3-1, page 3-5, and Figure 3-2, page 3- 7), may be desirable to obtain the optimum compromise between response speed and noise.

If the analyzer exhaust port is vented through a suitable absolute backpressure regulator, and the installation site is at or near sea level, barometric pressure changes do not affect the percent oxygen readout. If conditions are otherwise, the pressure compensation circuit must be re-calibrated per Section 3-4d, page 3-8.

3-9 CALIBRATION FREQUENCY

The appropriate calibration interval will depend on the accuracy required in the particular application, and is best determined by keeping a calibration log.

3-14

Operation

Rosemount Analytical Inc. A Division of Emerson Process Management