Instruction Manual

245364-V May 2002

Model 755A

3-6 DUAL ALARM OPTION

a.Initial Calibration and Selection of Setpoints for Alarms

The ALARM 1 and ALARM 2 circuits have independent setpoint and deadband adjustments (see Table 3-1, page 3-5, and Figure 3-2, page 3-7). Initially the ALARM 1 and ALARM 2 setpoint adjustments must be calibrated by means of the ALARM 1 and ALARM 2 calibration adjustments.

1.Set TEST switch to NORM.

2.Pass upscale standard gas through the analyzer at a flow rate of 50 to 500 cc/min.

3.Verify that ALARM 1 and ALARM 2 deadband adjustments are fully counterclockwise to set deadband at minimum. Normally these potentiometers are factory-set for minimum deadband. Both potentiometers must remain at this setting throughout calibration of the alarm setpoints.

Calibration of ALARM 1, HIGH:

Rotate setpoint adjustment R64 full counterclockwise.

Adjust SPAN control to obtain a display or recorder reading exactly fullscale. If the fullscale setting cannot be reached, then set to a reading higher than the desired alarm setpoint.

Set ALARM 1 calibration adjustment, R63, to its clockwise limit. Turn R63 counterclockwise the minimum required to energize ALARM 1 (relay K1, Figure 3-4, page 3-13). Energization may be verified by connecting an ohmmeter to relay terminals on 638254 Alarm Relay Assembly (Figure 2-1, page 2-2).

Calibration of ALARM 2, LOW:

1.Rotate setpoint potentiometer R67 full counterclockwise.

2.Adjust SPAN control to obtain a display or recorder reading exactly fullscale. . If the fullscale setting cannot be reached, then set to a reading higher than the desired alarm setpoint.

3.Set ALARM 1 calibration adjustment, R67, to its clockwise limit. Turn R63 counterclockwise the minimum required to energize ALARM 1 (relay K1, Figure 3-4, page 3-13). Energization may be verified by connecting an ohmmeter to relay terminals on 638254 Alarm Relay Assembly (Figure 2-1, page 2-2).

Setpoint of ALARM 1, HIGH

1.With span gas flowing, adjust SPAN Control to read desired alarm setpoint on display or recorder.

2.Turn setpoint adjustment, R64, clockwise to energy relay.

3.Check this setting by adjusting the SPAN Control to lower the output below the setpoint. This will re- energize the relay. Turning R64 above the setpoint will energize the relay.

Setpoint of ALARM 2, LOW

1.With span gas flowing, adjust SPAN Control to read desired alarm setpoint on display or recorder.

2.Turn setpoint adjustment, R68, clockwise to energy relay.

3.Check this setting by adjusting the SPAN Control to lower the output below the setpoint. This will re- energize the relay. Turning R68 above the setpoint will energize the relay.

3-12

Operation

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