Desco EMIT 50555 User manual

DESCO EMIT WEST - 3651 WalnutAvenue, Chino, CA 91710 • [phone] • Fax [phone]
DESCO EMIT EAST - 90 Hudson Road, Canton, MA 02021-1407 • [phone] • Fax [phone] • Web Site: DescoEMIT.com
TB-6521 02/07 Page 1 of 7
50555
OPERATOR'S MANUAL
CHARGED PLATE ANALYZER
Made in America
© 2007 DESCO INDUSTRIES INC.
Employee Owned

MODEL 268A-1
WARRANTY
Monroe Electronics, Inc., warrants to the Owners, this
instrument to be free from defects in material and
workmanship for a period of two years after shipment
from the factory. This warranty is applicable to the
original purchaser only.
Liability under this warranty is limited to service,
adjustment or replacement of defective parts (other
than tubes, fuses or batteries) on any instrument or
sub-assembly returned to the factory for this purpose,
transportation prepaid.
This warranty does not apply to instruments or sub-
assemblies subjected to abuse, abnormal operating
conditions, or unauthorized repair or modification.
Since Monroe Electronics, Inc. has no control over
conditions of use, no warranty is made or implied as to
the suitability of our product for the customer's
intended use.
THIS WARRANTY SET FORTH IN THIS ARTICLE IS
EXCLUSIVE AND IN LIEU OF ALL OTHER
WARRANTIES AND REPRESENTATIONS, EXPRESS,
IMPLIED OR STATUTORY INCLUDING BUT NOT
LIMITED TO THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. Except for
obligations expressly undertaken by Monroe
Electronics, in this Warranty, Owner hereby waives and
releases all rights, claims and remedies with respect to
any and all guarantees, express, implied, or statutory
(including without limitation, the implied warranties of
merchant-ability and fitness), and including but without
being limited to any obligation of Monroe Electronics
with respect to incidental or consequential damages, or
damages for loss of use. No agreement or
understanding varying or extending the warranty will be
binding upon Monroe Electronics unless in writing
signed by a duly authorized representative of Monroe
Electronics.
In the event of a breach of the foregoing warranty, the
liability of Monroe Electronics shall be limited to
repairing or replacing the non-conforming goods and/or
defective work, and in accor-dance with the foregoing,
Monroe Electronics shall not be liable for any other
damages, either direct or consequential.
RETURN POLICIES AND PROCEDURES
FACTORY REPAIR:
Return authorization is required for factory repair work.
Material being returned to the factory for repair must
have a Return Material Authorization number. To
obtain an RMA number, call 585-765-2254 and ask for
Customer Service.
Material returned to the factory for warranty repair
must be accompanied by a copy of a dated invoice or
bill of sale, which serves as a proof of purchase for the
material.
Repairs will be returned promptly. Repairs are
normally returned to the customer by UPS within ten
working days after receipt by Monroe Electronics, Inc.
Return (to the customer) UPS charges will be paid by
Monroe Electronics on warranty work. Return (to the
customer) UPS charges will be prepaid and added to
invoice for out-of-warranty repair work.
EXPEDITED FACTORY REPAIR:
All material returned to the factory by air or by an
overnight service will be expedited. Expedit-ed factory
repairs will be returned to the customer by the same
mode of transportation by which the material was
returned to the factory for repair (i.e., material returned
to the factory by an overnight service will be returned
to the customer by an overnight service).
NOTE: Return (to the customer) transportation
expenses for expedited factory repairs will always be
at the expense of the customer despite the warranty
status of the equipment.
FACTORY REPAIRS TO MODIFIED EQUIPMENT:
Material returned to the factory for repair that has been
modified will be not tested unless the nature and
purpose of the modification is understood by us and
does not render the equipment untestable at our repair
facility. We will reserve the right to deny service to any
modified equipment returned to the factory for repair
regardless of the warranty status of the equipment.
MONROE ELECTRONICS, INC.
100 HOUSEL AVENUE
LYNDONVILLE, NEW YORK 14098
PHONE [phone] [phone]
FAX [phone]

TABLE OF CONTENTS
Section 1 Specifications Page 1
Section 2 General Information Page 2
Section 3 Operation Page 4
Section 4 Maintenance Page 6
APPENDIX I Variable Timer Trip Point Option Page 7
Copyright© 1998
Monroe Electronics, Inc.
Printed in USA
P/N 0340097

Section 1
SPECIFICATIONS
CHARGED PLATE/PROBE ASSEMBLY:
• Designed to EOS/ESD Association standard
• Standard tripod mount
• Dimensions: 6" X 6"
• Capacitance: Total discharge test circuit with plate
20 picofarads, ±2 picofarads
• Plate self-discharge: Less than 10% of set voltage
within 5 minutes below 50% RH at 25°C
POWER SUPPLY:
±7500 volts maximum output; ±1000 volts/±5000 volts
charging of isolated plate available, adjustable from
<±1000 to >±5000 volts
ELECTROSTATIC FIELDMETER:
RANGE: 0 to ±7500 volts; 0 to ±2000 volts-switch
selectable
ACCURACY: Better than 2%
DRIFT: Less than 0.4% per hour non-cumulative after
10 minutes stabilization
SPEED OF RESPONSE: Less than 100ms for 10% to
90% of full scale either range
OUTPUT: Divide input by 1000, impedance 100W
TIMER:
Full scale 999.9 sec. (>16 min.), 0.1 sec. resolution
POWER REQUIREMENTS:
117 or 220 volts ±10% (factory preset), 50/60 Hz, 5
watts
SIZE AND WEIGHT:
Height 6¾", Width 6¾", Depth 9½"; 5 lbs
Section 2
GENERAL INFORMATION
The Charged Plate Analyzer Model 268A separates
into two components connected by a ten-foot cable.
The top part with the plate attached contains the
fieldmeter portion of the instrument and may be placed
at the measurement site. The bottom part with the
controls and indicators may be placed in a convenient
operating location remote from the detector. To
separate the two components, release the two over-
center latches near the rear of the unit and lift up at the
rear of the top section.
A ¼-20-threaded receptacle is provided inside of the
top section for convenient tripod mounting.
Two foldout legs are provided underneath the bottom
of the control unit to elevate the front of the cabinet to
permit easy viewing of the meters.
Switches on the front panel are alternate action push-
push type with the exception of the three used for
"plate control". These are mechanically interlocked so
that only one function can be selected at a time.
Controls are grouped by function.
The three pushbutton switches directly beneath the
"PLATE VOLTAGE" meter relate to meter range and
function.
The three switches at the lower center of the panel
labeled "PLATE CONTROL" affect the
charge/discharge condition of the plate.
The "HV" control knobs, the "HV ON" indicator and the
"POLARITY" pushbutton switch relate to the polarity
and magnitude of the initial charge voltage on the
plate.
The "TIMER LIMIT" switch sets the start/stop voltage
limits for the timer.
The "OUTPUT" BNC connector (on the back panel)
allows an oscilloscope or recorder to be connected to
the output of the fieldmeter. The signal here is
1/1000th of the actual voltage on the plate-regardless
of the settings of the meter range and function
switches.
Two small holes are provided in the plate for the
attachment of standard or miniature banana plugs,
useful for measuring induced charge or decay rate on
personnel.
268A-1 Rev. 11/98-RCA Page 1 268A-1 Rev. 11/98-RCA Page 2

IMPORTANT NOTE
In order to maintain proper operation of the floating
plate, it is essential that the support insulators be kept
scrupulously clean. Consider the following:
• Do not touch or handle the insulators.
• Do not wrap the line cord around the insulators.
• Store the instrument in its protective case when not
in use. Store in a clean dry location.
• Clean the insulators according to the directions given
in the MAINTENANCE section when self-discharge
exceeds 10% of the set voltage within 5 minutes at
relative humidity of less than 50%. At high humidity
surface leakage currents increase and air ionizes
readily and self-decay time can be expected to
decrease regardless of how clean the insulators are.
The Charged Plate Analyzer Model 268A meets test
equipment requirements of the EOS/ESD Association's
EOS/ESD STANDARD NO. 3.1 "STANDARD FOR
PROTECTION OF ELECTROSTATIC DISCHARGE
SUSCEPTIBLE ITEMS: IONIZATION".
Monroe Electronics, Inc. does not supply copies of
standards.
Copies of the standard are available from:
EOS/ESD Association, Inc.
7902 Turin Rd., Suite 4
Rome, NY 13440-2069
Phone [phone]
Fax [phone]
Section 3
OPERATION
BASIC OPERATION - DISCHARGE MODE:
1. Separate sections and position as necessary.
Connect to the proper power source and press "|"
on the power switch to apply instrument power. The
displays will indicate that power is on.
2. Select a polarity. For discussion purposes, we will
select positive. Press the POLARITY pushbutton in
to lock.
3. Select a range. We will use 5kV as an example.
Release the 5kV/2kV pushbutton under the PLATE
VOLTAGE meter.
4. Select NORMAL mode by releasing the NORM/PK
pushbutton (under the meter).
5. Select TIMER LIMIT. Release the TIMER LIMIT
pushbutton to set limits to 5kV and 500 volts. In
general, the setting of this function should concur
with the meter range selected.
6. Zero the plate by pressing the ZERO button. This
removes all voltage from the plate. (It connects the
plate to ground through a 10k-ohm resistor.)
7. Charge the plate. Press the CHARGE button. The
HV light indicates that the high voltage is on. The
PLATE VOLTAGE meter will indicate some voltage.
Adjust the voltage to a minimum of approximately
5kV +3% (5150 volts).
8. Allow the plate to decay. Press the DECAY
pushbutton. In the absence of ions, the plate will
decay very, very slowly. In a balanced ion field, the
plate will decay at a more rapid rate.
9. As the plate voltage crosses the +5000 volt level,
the timer will start. As the plate crosses the +500
volt level, the timer will stop and indicate the
elapsed time interval between these two levels.
Whenever the plate is recharged, the timer will be
reset for the next test.
268A-1 Rev. 11/98-RCA Page 3 268A-1 Rev. 11/98-RCA Page 4

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 Page 5 268A-1 Rev. 11/98-RCA Page 6

APPENDIX I
MODEL 268A-1T CHARGED PLATE ANALYZER
WITH VARIABLE TIMER OPTION
VARIABLE TIMER OPTION
The Model 268A-1T Charged Plate Monitor with
variable timer stop option has the same two timer
ranges as the standard unit when set in the "FIXED"
mode of operation. In the optional "VARIABLE" timer
mode, timing will start at either 5000 volts or 1000 volts
as selected by the user. The timer will then stop at a
user-selected voltage set on the front panel mounted
turns-counting dial from 0 to 1000 volts with 1-volt
increments.
This option is available either factory installed at the
time of purchase or as a factory installed aftermarket
upgrade to the basic Model 268A-1
VARIABLE TIMER OPTION OPERATING
INSTRUCTIONS
1. Power unit on.
2. Select either 5kV or 2kV plate voltage level
(measuring range).
3. Make sure NORM/PEAK button is in NORM
position (not depressed).
4. Set timer STOP LEVEL (turn pot) to desired plate
voltage stop level (0 to 1000 volts).
5. Press VARIABLE on TIMER LIMIT switch.
6. Select 5kV or 1kV timer start level on TIMER LIMIT
switch.
7. Select appropriate (+ or -) POLARITY for plate
voltage.
8. Press CHARGE button and adjust to voltage above
desired start voltage level.
9. Press DECAY button.
10. Observe PLATE VOLTAGE indicator as it decays.
Timer indicator (SECONDS) will stop when variable
trip point is met.
11. For additional tests, repeat steps 8 thru 10.
Note: To return unit to normal operation, switch unit
to FIXED on the TIMER LIMIT switch.
268A-1 Rev. 11/98-RCA Page 7