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Maintenance, Calibration and Troubleshooting
Maintenance
4
4-1
Section 4
Maintenance, Calibration and Troubleshooting
4.1 Maintenance
The 943-227-15 Digital Preamplifier is designed to operate for extended periods of time with no
scheduled maintenance required. Operation may be verified by periodically actuating the check source
(provided with the detector and sampling assembly) and observing the response of the unit. If the
response varies by more than 50% of the normal value, further troubleshooting may be required. If a
problem develops, troubleshoot the unit per Section 4.3 and the drawings in Appendix B.
Whenever the preamplifier enclosure is opened, the condition of the internal desiccant package should be
checked. The desiccant bag is provided in the enclosure to absorb moisture. The desiccant bags should
be checked for moisture absorption prior to placing into service, or whenever the electronics enclosure
cover is opened. Each bag contains a color indicator stripe that turns red when it should be replaced.
4.2 Electronic Calibration
Electronic Adjustments
There are no user adjustments available on the 943-227-15 Digital Preamplifier. The Programmable Gain
Amplifier and Auto Zero are factory adjustments, requiring the use of a factory test PROM and test fixture.
We strongly recommend the unit be returned to the factory for repair or adjustment.
Table 4-2 lists the electronic adjustments for the 943-227-15 digital preamplifier. The procedures for
making these adjustments are contained in the factory Calibration Procedure listed below. Note that
special test firmware is required to perform the electrical adjustments.
Table 4-1. Electronic Adjustments
Potentiometer Adjustment (943-227-15) Tolerance
R11 Programmable Gain Amplifier Offset Adjustment ± 2 mV
R12 Auto Zero Set-Up Adjustment ± 10 mV
NOTE
Refer to the drawings in Appendix B to locate adjustment
and/or test points, if required.
The follow factory calibration and test procedures are listed for reference only.
Document Description
TP943-227-15VL Test Procedure, Victoreen Loop Communications
TP943-227-15 Test Procedure, RS232 communications
TP977-200-15M Electrometer PCB Test Procedure