Instruction Manual

245364-V May 2002

Model 755A

c.Calibration with Downscale and Upscale Standard Gases

1.Set downscale calibration point as follows:

a.Set TEST switch (on analyzer door) to NORM.

b.Pass downscale standard gas through analyzer at suitable flow rate, preferably 250 cc/min. Allow gas to purge analyzer for minimum of 3 minutes.

NOTE:

The Zero and Span adjustments on the analyzer door are used only for the calibration of the digital readout for 0 to 100% oxygen.

The suppressed recorder ranges may only be set up after the digital readout has been calibrated. When setting up a suppressed recorder range, use only R41, R104 (setpoint) and R88 (Span) for adjustments. DO NOT RE-ADJUST THE ZERO AND SPAN CONTROLS ON THE ANALYZER DOOR.

c.Adjust ZERO Control so that the reading on the digital display or recorder is appropriate to the downscale standard gas. (The required reading may be the actual oxygen content of the downscale standard gas or may be an adjusted value, depending on the relative magnetic susceptibilities involved. Refer to Section 3- 5c, page 3-10). If proper reading is not obtained by an adjustment of the ZERO Control, refer to Section 6, Service and Maintenance.

2.Set upscale calibration point as follows:

a.Verify that front panel TEST switch is set to NORM.

b.Pass upscale standard gas through analyzer at same flow rate as was used for downscale standard gas. Allow gas to purge analyzer for minimum of 3 minutes.

c.Adjust SPAN Control so that reading on digital display or recorder is appropriate to the upscale standard gas. (The required reading may be the actual oxygen content of the upscale standard gas or may be an adjusted value, depending on the relative magnetic susceptibilities involved. Refer to Section 3-5c, page 3-10). If proper reading is unobtainable by adjustment of the SPAN control, refer to Section 6, Service and Maintenance.

Repeat steps 1 and 2 to ensure no interaction has occurred.

d.Calibration of Automatic Pressure Compensation

Oxygen readout is automatically corrected to within ±1% of fullscale for barometric pressure variations within

±3% of the target value and is corrected to within ±2% of fullscale for variations within ±5% of the target value. The target value may be set anywhere within the range of -2.7 to 3.3 psig ±3 psig (-

18.6to 22.8 kPa ±21 kPa). The factory setting is 0 psig (0 kPa). This setting is suitable for applications where (a) the analyzer exhaust port is vented directly to the atmosphere, and (b) the installation site is at or near sea level. If conditions are otherwise, the pressure compensation circuit must be re- calibrated by the following procedure:

3-8

Operation

Rosemount Analytical Inc. A Division of Emerson Process Management