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2471F
MEGOHMMETER
USER INSTRUCTION MANUAL
BARFIELD M/N 2471F
56-101-00220-B
September 23, 2008
________________________________________
BARFIELD, INC.
Corporate Headquarters
4101 Northwest 29th Street
Miami, Florida 33142
www.barfieldinc.com
Email: gsesales@barfieldinc.com
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2471F INSTRUCTION MANUAL
CONTACT INFORMATION
Users are requested to notify the manufacturer of any discrepancy, omission, or error
found in this manual. Inquiries should include specific questions and reference the
publication title, number, chapter, page, figure, paragraph, and effective date.
Please send comments to:
TECHNICAL CUSTOMER SUPPORT - GSTE
BARFIELD, INC.
P.O. BOX 025367
MIAMI, FL 33102-5367
USA
Telephone
(305) 894-5400
(800) 321-1039
Fax
(305) 894-5401
Email
gsesales@barfieldinc.com
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2471F INSTRUCTION MANUAL
ATTENTION
Although every effort has been made to provide the end user of this equipment with the most
current and accurate information, it may be necessary to revise this manual in the future. Please
be sure to complete and return a Revision Request Form to Barfield revision services and visit
the company website, http://barfieldinc.com/, for publication updates.
Additionally, Barfield MUST have your name and address on file as a registered user of this
equipment to ensure validation of the warranty. Please complete the OWNER WARRANTY
REGISTRATION card promptly. This card ensures validation of the warranty.
Please send to:
Barfield, Inc.
P.O. Box 025367
Miami, FL 33102-5367
USA
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Attention
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2471F INSTRUCTION MANUAL
REVISION RECORD
REV.
ECO #
REV. DATE
A
N/A
June 1986
B
260-00729
Sep / 23 / 2008
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DESCRIPTION OF CHANGE
Initial Release.
Company logo and contact information was updated.
Chapters were reorganized.
Rev.
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LIST OF APPROVED REPAIR FACILITIES
The manufacturer of this equipment does not recommend the user to attempt any maintenance
or repair. In case of malfunction, contact the manufacturer, to obtain the list of approved repair
facilities worldwide, ensuring that this equipment will be serviced using proper procedures and
certified instruments. A Return Maintenance Authorization (RMA) number will be assigned during this call, to keep track of the shipment and the service.
BARFIELD PRODUCT SUPPORT
DIVISION
Telephone
(305) 894-5400
(800) 321-1039
Fax
(305) 894-5401
Shipping Address:
Barfield, Inc.
4101 NW 29th Street
Miami, Florida 33142
USA
Mailing Address:
Barfield, Inc.
P.O. Box 025367
Miami, FL 33102-5367
USA
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Maint.
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TABLE OF CONTENTS
Contact Information
Attention Page
Revision Record Page
List of Approved Repair Facilities
Table of Contents
List of Figures and Tables
CHAPTER
............................................................................................PAGE
INTRODUCTION
1.
PUBLICATION BREAKDOWN .....................................................................1
2.
INFORMATION PROVIDED WITH THE UNIT .............................................1
3.
RECERTIFICATION .....................................................................................3
1
PRODUCT DESCRIPTION
1.
GENERAL ....................................................................................................5
2.
THEORY.......................................................................................................6
3.
SPECIFICATIONS........................................................................................6
2
OPERATING INSTRUCTIONS
1.
GENERAL ....................................................................................................9
2.
APPLICATION NOTES ...............................................................................10
3.
CARE AND MAINTENANCE.......................................................................11
3
RECEIVING, SHIPPING, AND STORAGE
1.
RECEIVING.................................................................................................13
2.
SHIPPING ...................................................................................................13
3.
STORAGE ...................................................................................................13
LIST OF FIGURES AND TABLES
Page
Figure 1: Identification Label...............................................................................................................1
Figure 2: Owner Warranty Registration Card......................................................................................2
Figure 3: Limited Warranty Statement Card .......................................................................................2
Figure 4: General View of the Megohmmeter 2471F..........................................................................5
Table 1: Current Consumption during Resistance Measurement ......................................................6
Table 2: Resistance Reading Parameters .........................................................................................6
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2471F INSTRUCTION MANUAL
INTRODUCTION
1. PUBLICATION BREAKDOWN
This user instruction manual establishes the standards of operation for Barfield’s 2471F
Megohmmeter.
Its purpose is to provide sufficient information for the personnel unfamiliar with this unit to
understand it, identify its parts, and operate it in accordance with proper procedures,
operating techniques, precautions and limitations.
2. INFORMATION PROVIDED WITH THE UNIT
Besides this User Instruction Manual, the instrument is provided with the four items described below.
A. The identification label, similar to Figure 1, is located on the back of the instrument and
provides the following information:
Manufacturer Name
Designation of Equipment
Equipment Part Number
Equipment Model Number
Equipment Serial Number
Equipment Modification (if applicable)
Equipment Options (if applicable)
459-00043 rev. B
a Sabena technics company
MEGOHMMETER TEST SET
P/N
M/N
101-00220
2471F
S/N
M A B C D E F G H J K
O
D L M N O P Q R S T U
MADE IN
THE USA
O A B C D E F
P
T G H J K L M
Figure 1: IDENTIFICATION LABEL
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2471F INSTRUCTION MANUAL
B. The Owner's Warranty Registration card (Figure 2) is to be completed by the owner and
returned to Barfield, Inc. within ten (10) days of purchase to ensure automatic update of
printed matter and validation of warranty.
Figure 2: OWNER WARRANTY REGISTRATION CARD
C. The Limited Warranty Statement Card (Figure 3) lists the manufacturer's obligation to
the original purchaser.
Figure 3: LIMITED WARRANTY STATEMENT CARD
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D. The Certificate of Calibration: Each new unit and re-certified unit, is delivered with a Certificate of Calibration that shows the date of the last calibration and when the next calibration is due. It certifies the accuracy of the unit and lists the part number and serial
number to which it applies.
3. RECERTIFICATION
This instrument has a one-year recertification requirement. Qualified technicians in a shop
equipped with the necessary tooling and facilities must perform the maintenance required by
this unit.
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CHAPTER 1: PRODUCT DESCRIPTION
1. GENERAL
(1)
The 2471F (Fig. 4) is a self-contained, battery operated, high potential megohmmeter.
Test potentials of 100, 200, and 500 volts DC are selectable by a panel switch. Current
limiting circuitry provides safe, ABSOLUTELY SHOCK-PROOF operation.
(2)
A single four inch meter scale, increasing from zero at the left to infinity at the right, is
incremented from .5 to 1,000 megohms. A pushbutton on the high potential test probe
provides for conveniently activating the instrument. Flashlight type batteries are used,
and a self-contained battery test is incorporated. Solid-state circuitry provides the
means for size reduction, high sensitivity, and dependability. The meter is a ruggedized taut-band suspension type, which eliminates the need for pivots and jewels. The
high potential probe is shield-guarded so that stray leakage through lead insulation will
not affect the measurement accuracy.
(3)
The output current of the 2471F is limited to a maximum of 30 microamperes even at
the 500 volt test potential. This current is well below human sensibility, so that there is
no sensation of current if the bare probes are touched with the tester activated. This
current limiting prevents damage to any circuitry or components that can withstand the
applied voltage, and prevents additional damage to a circuit that exhibits any insulation
deterioration.
(4)
The 2471F is also protected from damage due to inadvertently connecting the probes
across an energized circuit. AC or DC voltages up to 300 volts can be safely applied.
Figure 4: General View of the Megohmmeter 2471F
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2. THEORY
A transistor converter increases the battery supply to the 100, 200, and 500 volt test potentials selected by the panel switch. A high performance operational amplifier increases the
impedance and sensitivity of the panel meter to measure the voltage drop across the test
probes in terms of resistance. A panel control adjusts the calibration for infinity with the
probes removed from the circuit under test. The batteries are connected to the megohmmeter circuit through transistor switches activated by a subminiature pushbutton on the high potential probe. A single receptacle provides connection to all the test lead cable circuits, and
a shieldguard isolates the high potential lead from stray leakage resistance. A panel switch
connects the meter for testing of either of the battery circuits or for megohmmeter indication.
3. SPECIFICATIONS
(1)
The electrical specifications of the instrument are indicated in Tables 1 and 2.
Table 1: Current Consumption during Resistance Measurement
Test Potential (V)
Max. Draw (µA)
100 ± 10%
6
200 ± 10%
12
500 ± 10%
30
Table 2: Resistance Reading Parameters
Resistance Reading Range (MΩ)
0 to ∞
Reading Accuracy
± 10 %
Megohm Increments
(2)
Low
0.5
Midscale
17
High
1000
The physical specifications of the instrument are as follows.
•
Weight: 3.8 lbs., approx. (with carrying case)
•
Size:
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(3)
(4)
Accessories supplied with the instrument are as follows.
•
Portable vinyl overall carrying case, Eveready type, with test cable compartment.
•
Plug-in test cable leads.
•
Separable probe clip.
Batteries required for instrument operation are as follows.
•
3 each of 1.5 volt C cells (Eveready E93, or equivalent)
•
3 each of 1.5 volt AA cells (Eveready E91, or equivalent)
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CHAPTER 2: OPERATING INSTRUCTIONS
CAUTION: DO NOT APPLY HIGH VOLTAGE TESTS TO CIRCUITRY NOT DESIGNED FOR
HIGH VOLTAGE APPLICATION. MOST SOLID CIRCUITRY IS SUBJECT TO
DAMAGE FROM EVEN MOMENTARY APPLICATION OF HIGH VOLTAGE.
MAKE CERTAIN DEVICE UNDER TEST IS CLEAN. DIRT, MOISTURE, AND
MOST DEPOSITS EXHIBIT RATHER LOW LEAKAGE RESISTANCE.
1. GENERAL
(1)
Consult component manufacturer's testing specifications for test voltage to be applied.
Isolate the device under test from external power or circuitry.
(2)
Insert test cable plug fully into receptacle at the top of the test set.
(3)
Make certain meter pointer is resting at zero. (Adjust meter pointer zero adjust screw
on meter cover bezel, if necessary).
(4)
Select FUNCTION switch to B1 and then to B2 to read battery condition.
(a)
A reading above BATT. OK radial on the meter dial is satisfactory.
NOTE: Always return the FUNCTION switch to the MEGOHMS position after a
battery test to avoid small amount of battery drain.
(5)
Place FUNCTION switch on MEGOHMS for megohmmeter operation.
(6)
With RED test probe free from contact with external circuits or black probe, press
probe pushbutton, and then turn FULL SCALE ADJUST as required to produce full
scale deflection of meter pointer.
CAUTION: THIS ADJUSTMENT MUST BE RECHECKED WHENEVER A DIFFERENT VOLTAGE SELECTION IS MADE.
(7)
Connect BLACK probe to low, common, or ground side of circuit to be tested. (If both
sides of circuit to be tested are high, either point may be contacted with black probe).
Insert accessory clip on black probe, if more convenient.
(8)
Connect RED probe to other test point, and with pushbutton depressed, read insulation resistance in megohms on meter scale.
(a)
Consult component manufacturer's specifications for acceptable insulation resistance.
CAUTION: WAIT FOR METER TO COME TO FULL REST BEFORE READING.
THERE MAY BE A MOMENTARY DELAY AFTER BUTTON IS
PRESSED FOR HIGH VOLTAGE CONVERTER TO COME UP TO
FULL POTENTIAL, AND CAPACITANCE IN THE CIRCUIT UNDER
TEST MAY REQUIRE CHARGING TIME.
(9)
Consult the Application Notes (Next Section) for further details on specific application
of the 2471F to insulation testing.
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2. APPLICATION NOTES
(1)
Insulation sometimes will exhibit different leakage resistance with different test potentials applied. A reduced resistance reading with an increased setting of the VOLTS
switch is a normal condition in such cases.
(2)
If the probes are connected across an appreciable value of capacitance, the meter will
respond very slowly as a reaction to the charging time of the capacitor (approximately
5 seconds are required for 0.1 µF and 1 minute for 1 µF). If higher capacitance values
are to be tested, the capacitor should first be charged to the test voltage before applying the megohmmeter. Be certain to connect the RED probe to the positively charged
capacitance terminal, and wait for the voltage across the capacitance to equalize to
the megohmmeter test potential as indicated by an on-scale steady reading on the meter.
(3)
Even the slightest amount of electrical continuity to the bare red probe from a circuit
not part of that being measured will introduce erroneous readings. Exercise care not to
touch the bare end of the red probe or any circuitry not connected to the black probe
while testing. Make certain that no part of the device under test is inadvertently
grounded other than that which is normal ground.
(4)
When testing devices that have been exposed to moisture or dirt, low insulation resistance will often be indicated. Complete cleaning and dry baking at a temperature about
50°F above ambient will generally remove this source of leakage. In hot wet climates,
even superior insulations may have conductive paths through fungus growths. Cleaning and drying may remove most of such growths, but if the spores are not killed, the
growth may return in a few days. A fungus killing and growth inhibitor is recommended
in such cases.
(5)
A DC megohmmeter is not a substitute for an AC high-voltage break down tester. Alternating voltage strains an insulation in first one direction and then another. The behavior of the insulation under such strain is quite different from the application of a low
current DC test. In many applications, both types of test are required. If the device to
be tested is not subject to high voltages or high temperatures under normal operation,
high-voltage DC megohmmeter tests should suffice.
(6)
If a very low insulation resistance is indicated, a conventional ohmmeter should be
used for fault isolation. The lower operating voltage and low resistance readability of a
conventional ohmmeter is more satisfactory for finding direct or low resistance short
circuits
(7)
The normal deterioration of insulation results in a lowering of resistance with time.
Therefore, an insulation reading just slightly above a specified minimum, generally indicates an impending failure. Corrective measures should be taken to prevent further
deterioration. By recording periodic insulation measurements, deterioration trends will
be indicated so that preventative maintenance can be established.
(8)
Insulation minimums are generally specified (or implied) for dry atmospheric conditions. If the unit under test cannot be brought into a dry environment, or baked, reduced insulation resistance can be anticipated and allowances made accordingly.
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(9)
Sometimes insulation tests are required in polarized circuits that will exhibit low resistance when subjected to an opposite polarity. Consult the test specifications for polarity. The RED probe is always positive polarity from the megohmmeter. If in doubt,
make a test with probes connected in one manner and then reversed for a second test.
A substantial difference in reading will indicate a polarized circuit.
(10) If the megohmmeter indicates either an upward or downward scale reading with the
probes connected, but with the pushbutton released, the circuit under test is energized. (Small potentials may not produce a reading without button pressed but will introduce erroneous readings). Make certain that all power to the device has been removed and that all capacitances have been discharged. Some devices will retain residual voltages long after the power has been removed.
(11) Some tests require that jumpers be placed between two or more points on the device
under test while making insulation tests. This is generally done to prevent possible
damage to portions of the circuit that are not designed for high voltage application, or
to make an overall insulation test for a number of circuits simultaneously. Be certain to
follow the test specification procedures when jumpers are indicated.
3. CARE AND MAINTENANCE
The 2471F megohmmeter is designed to give lasting accurate performance provided reasonable care is exercised in operating and handling.
(1)
Keep test set in its carrying case at all times to reduce the danger of damage from vibration, shock, and moisture. Exercise reasonable care to avoid dropping or excessive
shock. Protect from rain and exposure.
(2)
Store in cool, clean, dry place to reduce contamination and battery deterioration. REMOVE BATTERIES IF TEST SET IS TO BE STORED FOR PROLONGED PERIODS.
(3)
Do not subject megohmmeter to electrically energized circuit. The 2471F is safe from
damage from externally applied AC or DC voltages up to 300 volts, but high voltages
may be dangerous to the operator and will produce erroneous readings.
(4)
Two sets of batteries are used. The three smaller AA cells (Eveready E91, or equivalent) provide the positive 4.5 volts for the operational amplifier and triggering of the battery transistor switches. The three larger C cells (Eveready E93, or equivalent) provide
the negative 4.5 volts for the operational amplifier and high voltage converter. The
2471F is designed for operation with alkaline type cells, but conventional zinc carbon
cells may be used as temporary replacements.
(5)
The B1 position of the FUNCTION switch connects the meter for testing the condition
of the C cells, and the B2 position for the AA cells. A reading below the BATT. OK radial on the meter scale is an indication of unsatisfactory battery condition. A more significant test may be made by observing the meter on the B1 and B2 positions with the
probe pushbutton depressed. The pointer will drop slightly on the B1 position, but
should remain above the BATT. OK radial. There should be no more than a barely
perceptible drop on B2 with the button depressed.
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(6)
To gain access to the batteries, release the strap across the top of the meter and remove tester from its carrying case. Place the test set in a clean area. (A clean cloth or
paper pad placed to the right of the test set to receive the inverted panel it desirable).
Remove the four corner panel screws. Withdraw the panel and rest it inverted to the
right of its case.
(7)
Push one of the battery holding clips aside while withdrawing the batteries. When replacing cells, make certain they are all inserted in the retainer tube in the same direction. The small terminal + (plus) end should connect to the RED terminal end of the respective battery holder.
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CHAPTER 3: RECEIVING, SHIPPING, AND STORAGE
1.
RECEIVING
No special unpacking procedures are necessary. It is recommended that the factory shipping
container and packing materials be retained should it become necessary for any reason to
reship the instrument.
It is also recommended to inspect carefully the instrument for damage. If damaged, do not
use it and immediately notify the carrier and the manufacturer.
2.
SHIPPING
Use standard delicate electronic equipment packaging procedures, when packing the
instrument for reshipment.
3.
STORAGE
Place a four-ounce bag of desiccant inside the carrying case (optional).
Store in a dry place with a temperature range of -10° C to +50° C.
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