Emerson Process Management 755R manual 4

Instruction Manual

748213-S April 2002

Model 755R

3-0	OPERATION .........................................................................................................................	3-1
3-1	Overview................................................................................................................................	3-1
3-2	Operating Range Selection ...................................................................................................	3-1
3-3	Startup Procedure .................................................................................................................	3-1
3-4	Calibration..............................................................................................................................	3-1
	a. Calibration with Zero and Span Standard Gases ...........................................................	3-1
3-5	Compensation For Composition Of Background Gas ...........................................................	3-2
	a. Oxygen Equivalent Value of Gases ................................................................................	3-4
	b. Computing Adjusted Settings for Zero and Span Controls.............................................	3-4
3-6	Selection Of Setpoints And Deadband On Alarm Option......................................................	3-7
3-7	Current Output Board (Option) ..............................................................................................	3-7
3-8	Routine Operation .................................................................................................................	3-8
3-9	Effect of Barometric Pressure Changes on Instrument Readout ..........................................	3-8
3-10	Calibration Frequency ...........................................................................................................	3-8

4-0	THEORY................................................................................................................................		4-1
4-1	Principles of Operation ..........................................................................................................		4-1
4-2	Variables Influencing Paramagnetic Oxygen Measurements ...............................................		4-2
	a.	Pressure Effects..............................................................................................................	4-2
4-3	Electronic Circuitry.................................................................................................................		4-4
	a.	Detector/Magnet Assembly.............................................................................................	4-4
	b.	Control Board and Associated Circuitry..........................................................................	4-4
	c.	Power Supply Board Assembly.......................................................................................	4-5
	d.	Isolated Current Output Board (Optional) .......................................................................	4-6

5-0	CIRCUIT ANALYSIS.............................................................................................................		5-1
5-1	Circuit Operation....................................................................................................................		5-1
5-2	±15 VDC 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 ........................................................................................		5-8
5-7	Buffer Amplifiers U8 and U10 with Associated Anticipation Function ...................................		5-10
5-8	Digital Output Circuit..............................................................................................................		5-10
5-9	Analog Output Circuits for Recorder and Alarms ..................................................................		5-11
	a.	First Stage Amplifier........................................................................................................	5-11
	b.	Second Stage Amplifier ..................................................................................................	5-11

6-0	MAINTENANCE AND SERVICE ..........................................................................................		6-1
6-1	Initial Checkout With Standard Gases...................................................................................		6-1
	a.	Control Board Checkout..................................................................................................	6-1
6-2	Heating Circuits .....................................................................................................................		6-2
	a. Case Heater Control Circuit ............................................................................................		6-2
6-3	Detector/Magnet Heating Circuit ...........................................................................................		6-2
6-4	Detector Check......................................................................................................................		6-4
	a.	Source Lamp...................................................................................................................	6-5
	b.	Photocell .........................................................................................................................	6-5
	c.	Suspension .....................................................................................................................	6-5

ii Contents Rosemount Analytical Inc. A Division of Emerson Process Management