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9.2 Null and Full-Scale Adjustments
The following procedures calibrate the null position and the full-scale position to the required output levels.
Refer to Figure 9-1 for the adjustment locations.
Figure 9-1
Location of Null & Scale Adjustments
and Terminal Boards on the AOM.
1. Disconnect all power from the system. Loosen the four screws securing the AOM cover, and remove
the cover.
2. Note the location of terminal board TB1 on the AOM (Refer to Figure 9-1). Connect a DVM (digital
voltmeter) across pins A and B of terminal board TB1 to monitor the displacement signal. Apply power
to the system
3. Position the permanent magnet at the specified null position. The null position is specified when the
LDT assembly is ordered (typically 2 inches from the transducer head).
4. Use a screwdriver to adjust the null potentiometer (R20) to increase or decrease the value, until you
obtain a DVM reading of 0.000 Vdc.
5. Position the permanent magnet for full-scale position (typically 2 inches from the end of the LDT
assembly).
6. Use a screwdriver to adjust the scale potentiometer (R24) to increase or decrease the value, until you
obtain a DVM reading of +10.000 Vdc.
7. Repeat steps 3 to 6 to check the null and full-scale settings. Readjust as necessary.
8. Disconnect the DVM and check overall system operation. If no more adjustments are necessary, replace
the AOM cover.
NOTE:
The following procedure assumes the
standard full-scale 0 to 10 Vdc output is
supplied. When other output signals are
supplied, use the appropriate signal levels
and test equipment for the following
adjustments.
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