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

to recorder and alarms. Note that on the circuit board the jumper positions are marked

 

Selection Jumper

according to the amplifier gain.

 

 

 

 

 

 

 

2

Recorder Zero

Used in combination with item 3 to establish required zero suppression to obtain desired

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

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.

Output Selection Jumper

 

 

 

 

6

Recorder Span

Provides ±5% span adjustment of recorder output.

Adjustment R88

 

 

 

 

 

 

 

7

CAL 1 Potentiometer

Used in calibration of automatic pressure compensation.

R98

 

 

 

 

 

 

 

8

CAL 2 Potentiometer

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

within the magnetic field. It is adjusted at the factory and does not require readjustment

Adjustment R9

 

except after replacement of detector.

 

 

 

 

 

 

 

10

Response Time

Provides adjustment range of 5 to 25 seconds for electronic response time (0 to 90% of

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.

At the factory, R29 is adjusted to establish the exact resistance ratio required and is

 

Potentiometer R29

then secured with locking compound.

 

 

 

 

 

 

 

 

12

ALARM 2 Calibration

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

accessory, for actuation of external, customer supplied alarm and/or control device(s).

Adjustment R68

 

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

limit) to 20% of fullscale (clockwise limit).

Deadband is essentially symmetrical with

Adjustment R78

 

respect to setpoint.

 

 

 

 

 

 

 

 

15

ALARM 1 Calibration

See item 12 above.

 

Adjustment R63

 

 

 

 

16

ALARM 1 Setpoint

See item 13 above.

 

Adjustment R64

 

 

 

 

17

ALARM 1 Deadband

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

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

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