Emerson 755A 38

Instruction Manual

245364-V May 2002

Model 755A

ITEM	CONTROL	DESCRIPTION

1	Recorder Oxygen Span	Provides selectable span of 100%, 20%, 10%, 5%, 2%, or 1% oxygen for analog output
1	Recorder Oxygen Span	to recorder and alarms. Note that on the circuit board the jumper positions are marked
	Selection Jumper	according to the amplifier gain.
		according to the amplifier gain.

2	Recorder Zero	Used in combination with item 3 to establish required zero suppression to obtain desired
2	Suppression Selection	range for analog output to recorder and	alarms. Jumper provides selectable zero
	Jumper	suppression of 20%, 40%, 60%, or 80%
3	Recorder Zero	Continuously adjustable from 0% to 25% oxygen. Thus the total suppression range is
	Suppression Coarse
	Suppression Coarse	0% to 105% oxygen.
	Adjustment R41	0% to 105% oxygen.
	Adjustment R41

	Recorder Zero
4	Suppression Fine	Adjustable range of 2%.
	Adjustment R104

5	Recorder Voltage	Provides selectable output of 10mV, 100mV, 1V or 5V for a voltage recorder.
5	Output Selection Jumper

6	Recorder Span	Provides ±5% span adjustment of recorder output.
6	Adjustment R88	Provides ±5% span adjustment of recorder output.
	Adjustment R88

7	CAL 1 Potentiometer	Used in calibration of automatic pressure compensation.
7	R98	Used in calibration of automatic pressure compensation.
	R98

8	CAL 2 Potentiometer	Used in calibration of automatic pressure compensation.
8	R99	Used in calibration of automatic pressure compensation.
	R99

9	Detector Coarse Zero	Provides coarse adjustment of detector zero by shifting the null position of the detector
	Detector Coarse Zero	within the magnetic field. It is adjusted at the factory and does not require readjustment
	Adjustment R9
	Adjustment R9	except after replacement of detector.
		except after replacement of detector.

10	Response Time	Provides adjustment range of 5 to 25 seconds for electronic response time (0 to 90% of
10	Adjustment R30	fullscale). Adjusting clockwise decreases response time.
	Adjustment R30	fullscale). Adjusting clockwise decreases response time.
11	Response Ratio Timing	Permits compensation for slight gain changes that may result from adjustment of R20.
11	Response Ratio Timing	At the factory, R29 is adjusted to establish the exact resistance ratio required and is
	Potentiometer R29	then secured with locking compound.
		then secured with locking compound.

12	ALARM 2 Calibration	Used for initial calibration of ALARM 2 circuit.
12	Adjustment R67	Used for initial calibration of ALARM 2 circuit.
	Adjustment R67
13	ALARM 2 Setpoint	Provides continuously variable adjustment of setpoint for ALARM 2 circuit on alarm
	ALARM 2 Setpoint	accessory, for actuation of external, customer supplied alarm and/or control device(s).
	Adjustment R68
	Adjustment R68	Adjustment range is 0 to 100% of fullscale span.
		Adjustment range is 0 to 100% of fullscale span.

14	ALARM 2 Deadband	Permits adjusting deadband of ALARM 2 circuit from 1% of fullscale (counterclockwise
	ALARM 2 Deadband	limit) to 20% of fullscale (clockwise limit).	Deadband is essentially symmetrical with
	Adjustment R78	limit) to 20% of fullscale (clockwise limit).	Deadband is essentially symmetrical with
	Adjustment R78	respect to setpoint.
		respect to setpoint.

15	ALARM 1 Calibration	See item 12 above.
15	Adjustment R63	See item 12 above.
	Adjustment R63
16	ALARM 1 Setpoint	See item 13 above.
16	Adjustment R64	See item 13 above.
	Adjustment R64
17	ALARM 1 Deadband	See item 14 above.
17	Adjustment R73	See item 14 above.
	Adjustment R73
8	Current Output Zero	Use to set zero-level current output, i.e., 4mA for 4 to 20mA board, 0mA for 0 to 20mA
8	Adjustment R1	board.
	Adjustment R1	board.
19	Current Output Span	Use to set fullscale current output at 20mA for 4 to 20mA or 0 to 20mA board or at
19	Adjustment R2	50mA for 10 to 50mA board.
	Adjustment R2	50mA for 10 to 50mA board.

Refer to Figure 3-2, page 3-7, for component locations.

Table 3-2. Model 755A Internal Adjustments

3-6

Operation

Rosemount Analytical Inc. A Division of Emerson Process Management