Instruction Manual

245364-V May 2002

Model 755A

3-0

OPERATION .........................................................................................................................

3-1

3-1

Overview................................................................................................................................

3-1

3-2

Selection of Recorder Oxygen Range...................................................................................

3-1

 

a. Recorder Oxygen Range Selection Procedure...............................................................

3-1

 

b. Readout of Applied Zero-Suppression Voltage on Digital Display .................................

3-3

3-3

Startup Procedure .................................................................................................................

3-4

3-4

Calibration..............................................................................................................................

3-4

 

a. Calibration Using Digital Readout for Oxygen Readout..................................................

3-4

 

b. Calibration Using Recorder for Oxygen Readout ...........................................................

3-4

 

c. Calibration with Downscale and Upscale Standard Gases ............................................

3-8

 

d. Calibration of Automatic Pressure Compensation ..........................................................

3-8

3-5

Compensation for Composition of Background Gas .............................................................

3-10

 

a. Oxygen Equivalent Values of Gases ..............................................................................

3-10

 

b. Oxygen Equivalents of Gas Mixtures..............................................................................

3-10

 

c. Computing Adjusted Settings for Zero and Span Controls.............................................

3-10

3-6

Dual Alarm Option .................................................................................................................

3-12

 

a. Initial Calibration and Selection of Setpoints for Alarms.................................................

3-12

 

b. Selection of Deadband....................................................................................................

3-13

3-7

Routine Operation .................................................................................................................

3-14

3-8

Effect of Barometric Pressure Changes on Instrument Readout ..........................................

3-14

3-9

Calibration Frequency ...........................................................................................................

3-14

4-0

THEORY................................................................................................................................

4-1

4-1

Principles of Operation ..........................................................................................................

4-1

 

a.

Magnetic Displacement Force ........................................................................................

4-1

 

b. Physical Configuration of Detector/Magnet Assembly....................................................

4-2

4-2

Variables Influencing Paramagnetic Oxygen Measurements ...............................................

4-5

 

a.

Pressure Effects..............................................................................................................

4-5

 

b.

Temperature Effects .......................................................................................................

4-5

 

c.

Interferents ......................................................................................................................

4-5

 

d.

Vibration Effects ..............................................................................................................

4-5

4-3

Electronic Circuitry.................................................................................................................

4-6

 

a.

Detector/Magnet Assembly.............................................................................................

4-6

 

b. Control Board and Associated Circuitry..........................................................................

4-6

 

c.

Case Board .....................................................................................................................

4-7

 

d. Isolated Current Output Board (Optional) .......................................................................

4-8

 

e.

Alarm Option ...................................................................................................................

4-8

5-0

CIRCUIT ANALYSIS.............................................................................................................

5-1

5-1

Overview................................................................................................................................

5-1

5-2

±15VDC Power Supply..........................................................................................................

5-1

5-3

Case Heater Control Circuit...................................................................................................

5-1

5-4

Detector Heater Control Circuit .............................................................................................

5-6

5-5

Detector Light Source Control Circuit....................................................................................

5-7

5-6

Detector with First Stage Amplifier and Pressure Compensation Circuits ............................

5-8

 

a.

Pressure Compensation Circuit ......................................................................................

5-9

 

b.

Pressure Signal Circuit ...................................................................................................

5-9

 

c. Positive and Negative Reference Voltage Circuits .........................................................

5-9

5-7

Buffer Amplifiers U10 and Associated Anticipation Function ................................................

5-11

5-8

Digital Output Circuit..............................................................................................................

5-12

5-9

Analog Output Circuits for Recorder and Alarms ..................................................................

5-12

ii

Contents

Rosemount Analytical Inc. A Division of Emerson Process Management