Monroe Electronics Electrostatic Fieldmeter - Static Monitor - model 177A - Manual (Page 83)

APNE-0016 82
Purge the Model 1036E probe through a ¼"-18 NPT tapped hole in the end of the housing
near the cable exit using common plumbing or tubing components.
Gas pressure to either probe type should be only great enough to produce a slight positive
flow out of the probe and in no event should it exceed a pressure of ½ psi.
Servicing
General
It must be emphasized that the critical elements of these probes (gradient cap and sensing
electrode) must be kept free from contaminants, e.g., dust, fumes, mists, or any foreign
material. The materials of which these elements are made were very carefully chosen to
minimize contact potential. Any foreign matter that will cause relative electrical activity when
combined with relative motion will tend to cause drift and measurement errors.
Therefore, it is recommended that:
 Probes be constantly purged even when not in use, if this is practical.
 Probes be kept tightly covered when not in use and are not being purged to
prevent contamination. A covering such as a plastic bag or aluminum foil may be
used. DO NOT cover the sensitive aperture with adhesive tape.
 Probes be cleaned only to the degree and frequency necessary to achieve the
required stability.
 Gradient caps NOT be removed for cleaning unless absolutely necessary.
 Major cleaning and reconditioning be performed by the factory.
Cleaning
The recommended cleaning solvent is clean 70-100% isopropyl alcohol applied with a
suitable soft, lint-free applicator. Use of a non-approved solvent may degrade performance
permanently, requiring factory service.
Outside surfaces of the probe should first be wiped clean with a lint-free wiping tissue
saturated in solvent. Then the interior surfaces should be flushed with solvent, using a
plastic squeeze bottle
7 , through the aperture until no dirt or dust may be seen. The probe
should then be allowed to drain and dry thoroughly. A 15-minute bake-out at 75°C is
recommended to remove residual solvent.
Model 1036E Disassembly/Assembly
In order to rewire the cable terminal block, replace, or standardize the probe assembly, it
must first be removed from its housing. This is done by loosening the four crosspoint screws
around the outer edge of the cover 1-1½ turns each, in turn, several times while lifting the
cover and probe straight out of the housing until it is completely removed. DO NOT attempt
to remove the screws completely one at a time. These four screws have circular "E-rings"
installed on them under the cover plate to make the screws captive and prevent their falling
into machinery below.
The probe assembly will need to be removed from the cover plate on the bench for
standardization, calibration, or to replace the gradient cap. This is done by removing the four
crosspoint screws that secure the phenolic mounting block to the hex standoffs, leaving the
standoffs attached to the cover plate.
To reassemble the probe unit, essentially reverse the above procedure. Once the phenolic
mounting block has been secured to the four hex standoffs, the probe unit should be
inspected to assure that an even gap exists completely around the gradient cap between the
gradient cap and the cover plate. If not, loosen the two crosspoint screws that secure the
probe body to the phenolic mounting block, and adjust the probe body so that it is centered
and completely surrounded by an even air gap.
Partially mate the card-edge fingers into the terminal block connector in the housing and
tighten the four outer screws in the cover plate 1-1½ turns at a time until the assembly is
secured in the housing.
7
Soft plastic wash bottles with an attached nozzle are available from scientific supply distributors.