Model 755A

Instruction Manual

245364-V May 2002

Pressure

 

F1

Compound Range

 

 

 

Pressure Gauge or

 

Gauge

 

 

Mercury Manometer

 

 

 

 

 

Vacuum

PR1

 

 

 

Pump

 

 

Sample

 

Sample In

 

 

 

 

250

In 755A

 

10 psig

V1

V3

cc/min

 

 

 

 

 

 

 

V2

V4

Figure 3-3. Calibration by Pressure Decrease Setup

Standard Procedure: Calibration by Pressure Decrease

1.Verify that the Pressure Compensation Option is selected, i.e., Jumper inserted between E1 and E3 on the Control Board.

2.Connect a compound range pressure gauge (or mercury manometer), pressure gauge, pressure regulator, flowmeter, needle valves and vacuum pump as shown in Figure 3-3 above.

3.Open V2, set PR1 to approximately 10 psig (69 kPa) and adjust V1 for a flow rate of 250 cc/min. into the sample inlet line. Compound range pressure gauge (or mercury manometer) should indicate close to atmospheric pressure (0.00).

4.Set TEST switch to PRESS CAL 1 and adjust CAL 1 potentiometer R98 (see Table 3-2, page 3-6, and Figure 3-2, page 3-7) for a reading of 00.00±5 counts on the display.

5.Set TEST switch to NORM and note display reading.

6.Start vacuum pump.

7.Close V2 and adjust V3 and V4 to decrease the pressure on the sample exhaust by about 3%. (- 12.00 inches of water; -0.4 psi; -23 mm of mercury; -3 kPa).

8.Adjust CAL 2 potentiometer R99 (see Table 3-2, page 3-6, and Figure 3-2, page 3-7) until reading on display is the same noted in step 5.

9.Repeat steps 3 through 7 as many times as necessary to ensure repeatability of compensation calibration.

NOTE

Although not mandatory, it is desirable, in order to obtain maximum accuracy, that the oxygen concentration of the gas used during calibration be close to that of the process stream which is to be analyzed.

Rosemount Analytical Inc. A Division of Emerson Process Management

Operation 3-9