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User's Manual
Digital AC Clamp Meter
Model 38390
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Tech Support
Hotlines
781-890-7440 ext. 200
extech@extech.com
www.extech.com
WARRANTY
EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free of defects in parts and workmanship for one year from date of
shipment (a six month limited warranty applies on sensors and cables). If it should become necessary to return the instrument for service during or
beyond the warranty period, contact the Customer Service Department at (781) 890-7440 ext. 210 for authorization. A Return Authorization (RA)
number must be issued before any product is returned to Extech. The sender is responsible for shipping charges, freight, insurance and proper
packaging to prevent damage in transit. This warranty does not apply to defects resulting from action of the user such as misuse, improper wiring,
operation outside of specification, improper maintenance or repair, or unauthorized modification. Extech specifically disclaims any implied warranties
or merchantability or fitness for a specific purpose and will not be liable for any direct, indirect, incidental or consequential damages. Extech's total
liability is limited to repair or replacement of the product. The warranty set forth above is inclusive and no other warranty, whether written or oral, is
expressed or implied.
REPAIR AND CALIBRATION SERVICES
Extech offers complete repair and calibration services for all of the products we
sell. For periodic calibration, NIST certification or repair of any Extech product, call
customer service for details on services available. Extech recommends that calibration
be performed on an annual basis to ensure calibration integrity.
Copyright © 1999 Extech Instruments Corporation. All rights reserved
including the right of reproduction in whole or in part in any form.
38390 V1.1 4/02
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INTRODUCTION
Congratulations on your purchase of Extech’s 38390 AC Clamp Meter. This autoranging clamp meter measures AC
Current to 400A, DC/AC Voltage, Resistance, and Continuity. Proper use and care of this meter will yield years of reliable
service.
SAFETY
Safety Symbols
This symbol, adjacent to another symbol or
terminal, indicates the user must refer to the
manual for further information.
This symbol, adjacent to a terminal, indicates
that, under normal use, hazardous voltages
may be present
Double insulation
WARNING: This indicates that a potentially hazardous
condition which, if not avoided, could
result in death or serious injury.
CAUTION: This indicates that a potentially hazardous
condition which, if not avoided, could
result in injury or damage to the meter.
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Safety Precautions
WARNING: Improper use of this meter can cause damage, shock, injury or death. Read and understand this users
manual before operating the meter.
1. Always remove the test leads before making current measurements.
2. Always remove the test leads before replacing the batteries.
3. Inspect the condition of the jaws, test leads and the meter for any damage before operating the meter.
Repair or replace any damage before use.
4. Do not exceed the maximum rated input limits.
5. Use great care when making measurements especially when the voltages are greater than 25VAC rms
or 35VDC. These voltages are considered a shock hazard.
6. Always discharge capacitors and remove power from the device under test before performing Resistance
or Continuity tests.
7. Remove the batteries from the meter if the meter is to be stored for long periods.
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SPECIFICATIONS
Function Range Accuracy Remarks
AC Current 40.00A
400.0A
± (2% + 15 digits) Frequency: 50/60Hz;
660A overload protection
AC Voltage 400.0V
600V
± (1.5% + 10 digits) Frequency: 40Hz to 450Hz;
Input Z: 1MΩ; 660Vrms OL protect
DC Voltage 400.0V
600V
± (1% + 5 digits)
Input Z: 1MΩ;
660V overload protect
Resistance
0.3 to 400 Ω
± (1% + 5 digits) -1.1 to -1.3V open circuit;
600Vrms overload protect
Continuity
Audible tone <40Ω approximately
-1.1 to -1.3V open circuit;
600Vrms overload protect
Note: Accuracy specified as ± (% of reading + number of digits) at 64oF to 82oF (18oC to 28oC) and RH<80%
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Conductor Size 0.9" (23mm ) maximum
Operating principle Dual slope integration
Battery type 2 x 1.55V button (ICE LR-44, NEDA 116A or A76)
Battery Life 200 hours
Auto Power off After 30 minutes
Range Selection Automatic ranging
Display 3-3/4 digit (3999 Count) LCD
Overload Indication "OL"
Low Battery Indication Battery icon
Environmental conditions Installation Category II,Pollution degree 2,Altitude up to 2000 meters, Indoor
use only
Operating Temperature/Humidity 32 to 104F (0
o
C to 40oC) / <80% RH
Storage Temperature/Humidity 14 to 140F (-10
o
C to 60oC) / <70% RH
Dimensions 7.4 x 2.5 x 1.2” (188 x 62.5 x 30.5mm)
Weight 6.5 oz. (185g)
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METER DESCRIPTION
Symbols
AC Current or Voltage
DC Voltage
Continuity
H Display Data Hold
A Auto Range
Low Battery icon
Units
V Volt (voltage)
Ω Ohm (resistance)
A Amps (current)
Front panel
1. Jaw opening trigger
2. Function switch (OFF, A, V,
Ω)
3. COM input jack
4. Transformer Jaws
5. DATA HOLD key
6. AC/DC Selector key
7. LCD Display
8. VΩ input jack
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OPERATING INSTRUCTIONS
Precautions
1. Ensure that the selected meter function matches the measurement to be taken.
2. If the measured current is higher than the range selected for long periods, overheating may
occur compromising the safety and the operation of the meter’s internal circuits.
3. To avoid discharge risks and erroneous readings, do not measure current on high voltage
conductors (>600V).
AC Current Measurements
WARNING: Make sure that the test leads are disconnected from the meter’s terminals before
making current measurements with the clamp jaw.
1. Set the Function switch to the A range..
2. Press the trigger to open jaw. Fully enclose one conductor to be measured.
3. The clamp meter will automatically select the proper range (Auto Range).
4. Read the measured value from the LCD display.
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DC and AC Voltage Measurements
1. Set the Function Switch to the V position.
2. Press the AC/DC key (directly below the HOLD key) to select AC or DC Voltage. The meter will
show the selection with an AC or DC symbol (upper left side of LCD).
3. Insert the black test lead to the COM input jack and the red test lead to the V jack.
4. Connect the test leads in PARALLEL with the circuit to be measured.
5. Read the measured value from the LCD display.
Resistance and Continuity Measurements
CAUTION: Before taking any in-circuit resistance measurements, remove power from the circuit under
test and discharge all capacitors.
1. Set the Function switch to the Ω position.
2. Insert the black test lead to the COM input jack and the red test lead to the Ω input jack.
3. Connect test leads to the device to be measured.
4. Read the measured value from the LCD display.
5. If the resistance is < 40Ω (approx.) an audible signal will be heard.
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Data Hold
Press the HOLD key momentarily to freeze the present reading on the LCD. "H" will appear in the display. Press the
HOLD key again to return to normal operation.
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MAINTENANCE
WARNING: To avoid electrical shock or damage to the meter, keep moisture from entering the meter housing. Also,
remove the test leads before opening the meter housing.
Cleaning
Periodically wipe the case with a damp cloth and mild detergent. Do not use abrasives or solvents.
Battery Replacement
When the low battery symbol appears on the LCD, replace the meter’s two button-batteries.
1. Remove power and remove test leads from meter
2. Remove the two rear Phillips screws and open the meter housing.
3. Remove and replace the two 1.55V button batteries per the following illustrations.
4. ICE replacement number: LR-44; NEDA replacement numbers: 116A or A76.
5. Replace the rear screws.
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Battery Replacement Illustrations
1. Slide battery to right
2. Press on other side to lift battery
3. Remove battery
4. Insert battery on angle
5. Press to seat battery
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