Monroe Electronics Electrostatic Voltmeter - Isoprobe® - model 244A - Manual (Page 20)

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APPENDIX III
MODEL 1017 PROBE CLEANING PROCEDURES
DISASSEMBLY AND CLEANING:
It is impossible for the sensitive aperture in the probe to be covered by a window of any
sort which will permit the probe to operate normally.
So long as this aperture is open, foreign material may enter the volume associated with
the vibrating vane and generate undesired noise or DC offset, thereby impairing the
accuracy and utility of the instrument.
To maintain low noise and low offset, it is important that the probe be operated in as
clean an environment as practicable, that it be purged with filtered air or an inert gas
such as clean, dry nitrogen, and that it be periodically disassembled and cleaned.
Where practicable, it is recommended that the probe be installed with the sensitive
aperture downward and when not in use, wrapped with aluminum foil.
The necessity for cleaning is indicated when:
1. The output as indicated by the meter or the recorded record is excessively
noisy.
2. It is no longer possible to "null balance" the instrument using the BAL
adjustment and still remain within the range of the ZERO adjustment.
Cleaning Procedure #1
1. Disconnect probe cord from main unit.
2. Remove probe from fixturing device if used.
3. Remove screw closest to sensitive aperture and loosen screw closest to
cable end.
4. Carefully slide cover directly off of probe.
NOTE: Some probes have one or more shims between the base and the
case. These will fall out of the case when it is removed. Retain them.
5. Once the case is removed and until it is replaced, the two vanes are
exposed and subject to damage, therefore, during cleaning VERY
CAREFUL HANDLING is required.
8. Cleaning should be done using an aerosol isopropyl alcohol or equivalent
solvent.
9. Areas to be checked for cleanliness are:
a. ) Sensitive electrode.
b. ) Two vanes, especially in the area of the sensitive electrode (both
sides).
c. ) The aperture in the case and surrounding area (inside and out).
6. CAREFULLY slide case back onto probe. Shim(s), if any, should be slid
into the case first in such a way that the hole in the shim(s) will be lined up
with the screw hole (in the case) closest to the aperture so that when the
screw is replaced, it will extend through the shim(s) before entering the
threaded hole in the probe base.
7. The toe of the base plate should abut the inner surface of the end of the
case.
8. Tighten screws with torque consistent with their size.