BASIC OPERATION - PEAK MODE:
Peak mode is useful for checking balance in pulse
ionizing systems. The timer is not associated with
these measurements. The internal high voltage
charging source is not normally used.
The switches used in making peak measurements are
the three selector switches under the PLATE
VOLTAGE meter and the ZERO and DECAY switches.
1. Select a meter range using the 5kV/2kV switch.
2. Zero the plate by depressing the ZERO switch.
3. Select desired peak (+ or -).
4. Select PEAK mode by depressing the NORM/PK
switch into the PK position.
5. Allow the plate to "float" by depressing the DECAY
button. This ungrounds the plate. The meter will
now indicate the highest peak voltage attained by
the plate in the selected polarity. The -PK/+PK
switch may be shifted to the opposite position to
read the highest peak voltage attained in that
polarity.
To balance your ionization system or blower, adjust
until both positive and negative peak readings are
the same.
6. Anytime the NORM/PK button is released to the
NORM position; the peak detector is automatically
reset.
7. The plate will continue to float until the ZERO button
is pressed. Thus, the ZERO switch and the RESET
function of the NORM/PK switch are normally used
in conjunction with each other.
Section 4
MAINTENANCE
GENERAL:
Field maintenance of Model 268A should be limited to
cleaning of the insulating standoffs, cleaning of the
case and occasional field-meter zero adjustment.
Further repairs and adjustment require special
equipment and are beyond the scope of this manual.
Factory service is advised.
CLEANING, INSULATORS:
The insulating standoffs (supporting the measuring
plate) are specifically designed to minimize the effects
due to contamination of their outer surfaces. Leakage
paths created by the skin oils in fingerprints, tobacco
smoke, dust, etc. will eventually degrade their
performance such that the self-decay rate of the plate
will exceed 10% over a five-minute period, indicating
the need for cleaning.
IMPORTANT!
DO NOT USE SOAP, DETERGENT OR TAP WATER
TO CLEAN THESE INSULATORS
Clean the exposed surfaces of the insulators with
mixture of 70% clean technical grade isopropyl alcohol
and 30% distilled water, using a soft toothbrush. The
unit should be inverted while doing this to minimize the
amount of liquid entering the case.
The insulators should then be allowed to air-dry.
CLEANING, CASE:
General cleaning of the case for aesthetic reasons is
best done with a clean lint-free cloth or wiping pad
dampened in the alcohol/water solution noted above.
FIELDMETER ZERO:
Airborne contaminants entering the sensitive aperture
of the fieldmeter probe may cause a zero shift, which
will affect the accuracy of measurement.
A multi-turn potentiometer is provided on the upper
section of the instrument to adjust fieldmeter zero.
Adjust for an indication of zero volts on the 2000 volt
meter range with the ZERO button pressed in.
268A-1 Rev. 11/98-RCA
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268A-1 Rev. 11/98-RCA
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