Fluke 381 User manual

PN 3538357
July 2010
© 2010 Fluke Corporation. All rights reserved. Printed in China. Specifications are subject to
change without notice. All product names are trademarks of their respective companies.
381
Remote Display
True-rms
Clamp Meter
Users Manual

LIMITED WARRANTY AND LIMITATION OF LIABILITY
This Fluke product will be free from defects in material and workmanship for three years from the
date of purchase. This warranty does not cover fuses, disposable batteries, or damage from
accident, neglect, misuse, alteration, contamination, or abnormal conditions of operation or
handling. Resellers are not authorized to extend any other warranty on Fluke’s behalf. To obtain
service during the warranty period, contact your nearest Fluke authorized service center to obtain
return authorization information, then send the product to that Service Center with a description of
the problem.
THIS WARRANTY IS YOUR ONLY REMEDY. NO OTHER WARRANTIES, SUCH AS FITNESS
FOR A PARTICULAR PURPOSE, ARE EXPRESSED OR IMPLIED. FLUKE IS NOT LIABLE
FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSSES,
ARISING FROM ANY CAUSE OR THEORY. Since some states or countries do not allow the
exclusion or limitation of an implied warranty or of incidental or consequential damages, this
limitation of liability may not apply to you.
Fluke Corporation
P.O. Box 9090
Everett, WA 98206-9090
U.S.A.
Fluke Europe B.V.
P.O. Box 1186
5602 BD Eindhoven
The Netherlands
11/99

i
Table of Contents
Title Page
Introduction................................................................................................................. 1
How to Contact Fluke ................................................................................................. 1
Safety Information ...................................................................................................... 2
Radio Frequency Data ............................................................................................... 7
Features ..................................................................................................................... 8
Remote Display ...................................................................................................... 8
Hazardous Voltage Indicator .................................................................................. 10
Flexible Current Probe ........................................................................................... 10
Auto Power Off ....................................................................................................... 10
Backlight................................................................................................................. 11
Display Hold ........................................................................................................... 11
MIN MAX AVG ....................................................................................................... 11
DC Current Zero..................................................................................................... 11
Inrush ..................................................................................................................... 12
Low Battery Indicators............................................................................................ 12

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Display.................................................................................................................... 17
Measurements............................................................................................................ 19
AC and DC Current (Jaw) ...................................................................................... 19
AC Current (Flexible Current Probe)...................................................................... 22
AC and DC Voltage ................................................................................................ 23
Resistance/Continuity............................................................................................. 26
Inrush Current Measurement (Jaw and Flexible Current Probe) ........................... 26
Frequency Measurement (Jaw and Flexible Current Probe) ................................. 28
Maintenance............................................................................................................... 28
Cleaning the Meter and Flexible Current Probe..................................................... 28
Battery Replacement.............................................................................................. 29
User-Replaceable Parts ............................................................................................. 31
Specifications ............................................................................................................. 32
Electrical Specifications.......................................................................................... 32
Mechanical Specifications...................................................................................... 37
Environmental Specifications ................................................................................. 38

1
Introduction
XWWarning
Read "Safety Information" before you use the Meter.
The Fluke 381 is a handheld, battery-operated Clamp Meter (the Meter) that has a remote-display
module and detachable iFlex (Flexible Current Probe). The Remote Display can be removed from
the Meter body and read away from the measurement source. This lets the display be easily read
in difficult-measurement situations such as a hazardous environments, or very tight spaces. The
Flexible Current Probe makes it possible to measure higher current (up to 2500 A ac) and larger
cables that traditional jawed meters cannot measure.
How to Contact Fluke
To contact Fluke, call one of the following telephone numbers:
•Technical Support USA: 1-800-44-FLUKE (1-800-443-5853)
•Calibration/Repair USA: 1-888-99-FLUKE (1-888-993-5853)
•Canada: 1-800-36-FLUKE (1-800-363-5853)
•Europe: [phone]
•Japan: [phone]

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•Singapore: [phone]
•Anywhere in the world: [phone]
Or, visit Fluke's website at www.fluke.com.
To register your product, visit http://register.fluke.com.
To see, print, or download the latest manual supplement, visit
http://us.fluke.com/usen/support/manuals.
Safety Information
A Warning identifies conditions and actions that pose hazard(s) to the user; A Caution identifies
conditions and procedures that could cause Meter damage, equipment under test damage, or
permanent loss of data.
Symbols used on the Meter and in this manual are explained in Table 1.
XWWarning
To prevent possible electrical shock or personal injury, follow these guidelines:
•Use the Meter only as specified in this manual or the protection provided by the
Meter can be compromised.
•Examine the case before you use the Meter. Look for cracks or missing plastic.
Carefully look at the insulation around the connectors.
•Never measure ac current while the test leads are inserted into the input jacks.
•Make sure the battery door is closed and latched before operating the Meter.
•Remove the test leads from the Meter before the battery door is opened.

Remote Display True-rms Clamp Meter
Safety Information
3
•Examine the test leads for damaged insulation or exposed metal. Check test lead
continuity. Replace damaged test leads before using the Meter.
•Do not use the Meter if it operates incorrectly. Protection can be compromised.
When in doubt, have the Meter serviced.
•Do not use the Meter around explosive gas, vapor or in damp or wet
environments.
•Use only type AAA batteries, properly installed in the Meter case, to power the
Meter.
•To avoid false readings that can lead to electrical shock and injury, replace the
batteries as soon as the low battery indicator (Bor Q)
appears.
•When servicing the Meter, use only specified replacement parts. See Table 5.
•Have the Meter serviced only by qualified service personnel.
•Be careful around voltages > 30 V ac rms, 42 V ac peak, or 60 V dc. Such
voltages pose a shock hazard.
•Do not apply more than the rated voltage, as marked on the Meter, between the
terminals or between any terminal and earth ground.
•When using the probes, keep fingers behind the finger guards on the probes.
•Connect the common test lead before connecting the live test lead. When
disconnecting test leads, disconnect the live test lead first.
•Do not work alone so assistance can be rendered in an emergency.

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•Use extreme caution when working around bare conductors or bus bars. Contact
with the conductor could result in electric shock.
•Adhere to local and national safety codes. Individual protective equipment must
be used to prevent shock and arc blast injury where hazardous live conductors
are exposed.
•When measuring, keep fingers behind the Tactile Barrier. See Figure 2.
•Disconnect circuit power and discharge all high-voltage capacitors before you
do diode tests or measure resistance, continuity, or capacitance.
•Do not measure ac/dc current in circuits carrying more than 1000 V or 1000 A
with the Meter Jaw.
•Never operate the Meter with the back cover removed or the case open.
•Do not measure ac current in circuits carrying more than 1000 V or 2500 A with
the Flexible Current Probe.
•Do not apply the Flexible Current Probe around or remove from HAZARDOUS
LIVE conductors.
•Take special care during fitting and removal of the Flexible Current Probe. De-
energize the installation under test or wear suitable protective clothing.
WCaution
To avoid possible damage to the Meter or to equipment under test:
•Use the proper jacks, function, and range for the measurement application.

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Safety Information
5
Table 1. Symbols
Symbol Meaning Symbol Meaning
BAC (Alternating Current) JEarth ground
FDC (Direct Current) PAC and dc current.
XHazardous voltage PConforms to European Union
directives.
WRisk of Danger. Important
information. See Manual. )Conforms to relevant North American Safety Standards.
BBattery. Low battery when shown. TDouble insulated
~Do not dispose of this product as unsorted municipal waste. Go to Fluke’s website for
recycling information.

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Symbol Meaning Symbol Meaning
CAT III
IEC Measurement Category III
CAT III equipment has protection
against transients in equipment in
fixed-equipment installations, such
as distribution panels, feeders and
short branch circuits, and lighting
systems in large buildings.
CAT IV
IEC Measurement Category IV
CAT IV equipment has protection
against transients from the primary
supply level, such as an electricity
Meter or an overhead or underground
utility service.
®Examined and licensed by TÜV
Product Services. ;Conforms to relevant Australian standards.
-Do not apply to or remove from
HAZARDOUS LIVE conductors. ,Application around and removal from
HAZARDOUS LIVE conductors is
permitted.
Note
The Measurement Category (CAT) and voltage rating of any combination of test probe,
test probe accessory, current clamp accessory, and the Meter is the LOWEST rating of
any individual component.

Remote Display True-rms Clamp Meter
Radio Frequency Data
7
Radio Frequency Data
Note
Changes or modifications to the wireless 2.4 GHz radio not expressly approved by
Fluke Corporation could void the user's authority to operate the equipment.
This device complies with Part 15 of the FCC Rules. Operation is subject to the two conditions
that follow:
1. This device can not cause interference.
2. This device must accept any interference, including interference that can cause undesired
operation of the device.
Class B digital device: A digital device that is marketed for operation in a residential environment
not withstanding use in commercial, business and industrial environments. Examples of such
devices include, but are not limited to, personal computers, calculators, and equivalent electronic
devices that are marketed for operation by the general public.
The Meter was tested and found to comply with the limits for a Class B digital device, pursuant to
Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against
harmful interference in a residential installation. This equipment generates, uses, and can radiate
radio frequency energy and, if not installed and used in accordance with the instructions, can
cause harmful interference to radio communications. However, there is no guarantee that
interference will not occur in a particular installation. If this equipment does cause harmful
interference to radio or television reception, which can be determined by turning the equipment

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off and on, the user is encouraged to try to correct the interference by one or more of the
measures that follow:
•Reorient or relocate the receiving antenna.
•Increase the separation between the equipment and receiver.
•Consult the dealer or an experienced radio/TV technician for help.
The term "IC:" before the radio certification number only signifies the device meets Industry's
Canada technical specifications.
Features
The following sections explain the Meter features in detail. See Figure 2 and Table 2.
Remote Display
The Meter uses low-power 802.15.4 wireless technology to let the display module operate in a
different location than the Meter base. Although there is control of some Meter functions (Hold,
MIN MAX AVG, and Backlight), complete remote control of the Meter is not available through the
display module.
The wireless radio signal does not hinder Meter measurements. Usually, the radio signal is off
when the display module is docked to the Meter base. It is possible for the radio signal to be on
when the display module is docked and the Rotary Function Switch is set to OFF. To make sure
that the radio signal is off, remove the batteries from the Meter base and display module.
The display module is synchronized with a Meter base when it is docked on the Meter base and
turned on. Different display modules can be synchronized with a Meter base but, only one display
module can be synchronized to a Meter base at the same time.

Remote Display True-rms Clamp Meter
Features
9
The Meter base and display can be a maximum of 10 meters from each other before the radio
signal connection is broken. This distance can change with the obstacles between the Meter base
and display. There is a radio connection when shows in the display.
To detach the display from the Meter base, see Figure 1.
1
2
ghn10.eps
Figure 1. Remote Display

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Hazardous Voltage Indicator
When the Meter senses a voltage ±30 V or a voltage overload (OL), Yis shown on the display
and the red high-voltage LED () on the Meter base illuminates to tell you a hazardous voltage
is at the Meter input.
Flexible Current Probe
XWWarning
To avoid electrical shock, do not apply or remove from live hazardous
conductors.
The high-performance AC Flexible Current Probe utilizes the Rogowski principle and is used for
accurate, non-intrusive measurement of sinusoidal, pulsed, and other complex waveforms. The
flexible and lightweight measuring head allows quick and easy installation in hard-to-reach areas
and works well with large conductors.
For more information about the Flexible Current Probe, see “Current Measurement (Flexible
Current Probe)”.
Auto Power Off
The Meter powers off if there is no button push or Rotary Function Switch operation for
20 minutes. If the Meter powers off, turn the Rotary Function Switch OFF and then back on again.
Auto Power Off is disabled during Min Max Avg function use. To disable the Auto Power Off, hold
down while turning on the Meter.

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Features
11
Backlight
Push to toggle the Backlight on and off. The Backlight automatically goes off after 2 minutes.
To disable the Backlight Auto Off feature, hold down while turning on the Meter.
Display Hold
To capture and hold the present display reading, push while taking a reading. Push 
again to return to the live reading.
MIN MAX AVG
Min Max Avg mode can capture the minimum, maximum, and average readings of a given output
signal over an extended time.
Push to enter Min Max Avg mode, push again to toggle between min and max readings.
Push a third time to display the average reading. To exit Min Max Avg mode, push and hold 
for 2 seconds. When Min Max Avg mode is active, the Auto Power Off feature is disabled.
DC Current Zero
Push to remove any dc offset that could affect the accuracy of dc readings.

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Inrush
Inrush Current is surge current that occurs when an electrical device is first powered on. The
Meter can capture this surge current reading. Current spikes from motor drives are one example
of such an event. The Inrush function takes approximately 400 samples over a 100 ms period and
calculates the starting current envelope.
Low Battery Indicators
The Meter uses two low battery symbols: Band Q. When B
appears, the batteries in the Meter base should be changed. Low batteries on the Meter base will
affect the readings. When Qis displayed, the batteries for the removable display
should be changed. Measurements are not affected by low batteries in the display.

Remote Display True-rms Clamp Meter
Features
13
600V
CAT
10 0 0 V
CAT
10 0 0 A
ZERO
REMOTE DISPLAY
TRMS CLAMP METER
381
iFlex
1
16 14
15
345 6
9
12
13 10
11
7
8
2
ghn02.eps
Figure 2. Meter Features

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Table 2. Meter Features
Item Description
ACurrent sensing Jaw
BTactile Barrier
CRotary Function Switch, see Table 3.
DHazardous-voltage indicator
EDisplay release button
FDisplay
GBacklight button: turns the Backlight on and off. The Backlight stays on for
2 minutes when there is no button or switch interaction and then shuts off.
HHold button: freezes the display reading and releases the reading when pushed a
second time.
I
Min Max button: when first pushed, the Meter shows maximum input. With
subsequent pushes, the minimum and the average inputs are shown. Hold Lfor
2 seconds to exit min max mode. This function works in current, voltage, and
frequency modes.

Remote Display True-rms Clamp Meter
Features
15
Item Description
JZero/Shift button: removes dc offset from dc current measurements. Also used to
shift and corresponds to the yellow items on the Rotary Function Switch.
KInrush button: push to enter inrush mode. Push a second time to exit inrush mode.
Integration time is 100 ms.
LJaw release
MAlignment marks: to meet accuracy specifications, the conductor must be aligned
with these marks.
NCommon terminal
OVolts/Ohm input terminal
PFlexible Current Probe input terminal

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Table 3. Rotary Function Switch
Switch Position Function
OFF Meter is powered down
KAC voltage
LDC voltage
KResistance and continuity
AAC current. Push Zto shift to frequency.
CDC current
DAC current and frequency measurement using the Flexible Current Probe.
Push Zto shift to frequency.