Fluke 377 User manual

September 2020
©2020 Fluke Corporation. All rights reserved.
All product names are trademarks of their respective companies.
377/377 FC
378/378 FC
Clamp Meter
Users Manual
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 - TestEquipmentDepot.com

LIMITED WARRANTY AND LIMITATION OF LIABILITY
Each Fluke product is warranted to be free from defects in material and workmanship under normal use and service. The warranty period is three
years and begins on the date of shipment. Parts, product repairs, and services are warranted for 90 days. This warranty extends only to the
original buyer or end-user customer of a Fluke authorized reseller, and does not apply to fuses, disposable batteries, or to any product which, in
Fluke's opinion, has been misused, altered, neglected, contaminated, or damaged by accident or abnormal conditions of operation or handling.
Fluke warrants that software will operate substantially in accordance with its functional specifications for 90 days and that it has been properly
recorded on non-defective media. Fluke does not warrant that software will be error free or operate without interruption.
Fluke authorized resellers shall extend this warranty on new and unused products to end-user customers only but have no authority to extend a
greater or different warranty on behalf of Fluke. Warranty support is available only if product is purchased through a Fluke authorized sales outlet
or Buyer has paid the applicable international price. Fluke reserves the right to invoice Buyer for importation costs of repair/replacement parts
when product purchased in one country is submitted for repair in another country.
Fluke's warranty obligation is limited, at Fluke's option, to refund of the purchase price, free of charge repair, or replacement of a defective product
which is returned to a Fluke authorized service center within the warranty period.
To obtain warranty service, 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 difficulty, postage and insurance prepaid (FOB Destination). Fluke assumes no risk for damage in
transit. Following warranty repair, the product will be returned to Buyer, transportation prepaid (FOB Destination). If Fluke determines that failure
was caused by neglect, misuse, contamination, alteration, accident, or abnormal condition of operation or handling, including overvoltage failures
caused by use outside the product’s specified rating, or normal wear and tear of mechanical components, Fluke will provide an estimate of repair
costs and obtain authorization before commencing the work. Following repair, the product will be returned to the Buyer transportation prepaid and
the Buyer will be billed for the repair and return transportation charges (FOB Shipping Point).
THIS WARRANTY IS BUYER'S SOLE AND EXCLUSIVE REMEDY AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
FLUKE SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSSES, INCLUDING
LOSS OF DATA, ARISING FROM ANY CAUSE OR THEORY.
Since some countries or states do not allow limitation of the term of an implied warranty, or exclusion or limitation of incidental or consequential
damages, the limitations and exclusions of this warranty may not apply to every buyer. If any provision of this Warranty is held invalid or
unenforceable by a court or other decision-maker of competent jurisdiction, such holding will not affect the validity or enforceability of any other
provision.
11/99
Fluke Corporation
P.O. Box 9090
Everett, WA 98206-9090
U.S.A.

i
Title Page
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Contact Fluke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Safety Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Before You Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Terms to Know. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Fluke Connect™ (377 FC/378 FC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Radio Frequency Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Fluke Connect™ App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Features/Buttons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Auto Power Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Backlight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Power-On Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Maintenance Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Basic Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Hazardous Voltage Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Field Sense Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Field Sense AC Current, Voltage, and Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
L1-L2-L3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Power Health Indicator (378/378 FC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table of Contents

377/377 FC/378/378 FC
Users Manual
ii
AC/DC Voltage Measurement with Test Leads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Resistance/Continuity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
DC Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
iFlex Probe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Measurement Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Display Hold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
MIN/MAX/AVG Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Inrush Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Data Logging (377 FC/378 FC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Clear Memory (377 FC/378 FC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Firmware Update (377 FC/378 FC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Firmware Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
How to Clean the Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1
Introduction
The Fluke 377, 377 FC, 378, and 378 FC Current Clamp (the
Clamp or Product) provides:
• display with two simultaneous measurements (current and
voltage)
• grounding with a single lead
• live measurements with no circuit downtime
• non-contact voltage technology (measurement for Power
Health Indicator, power factor, and real power)
• wireless connectivity to smartphone for work-orders and
reporting integration with Fluke Connect™
The Clamp measures true-rms ac current and voltage, dc current
and voltage, inrush current, resistance, capacitance, frequency,
and dc millivolts.
The included iFlex (detachable, flexible current-probe) expands
the measurement range to 2500 A ac. The iFlex allows
measurements of awkward sized conductors and improved wire
access.
The illustrations in this manual show the 378 FC.
Table 1 is a list of features available for each model.
Table 1. Features by Model
Model 377 378 377 FC 378 FC
BLE for FC ••
Power Heath Indicator ••
Phase Rotation App Only App Only
Sequential phase - NC voltage
measurement ••••
Phase-to-phase voltage calculation ••••
True RMS ••••
Logging ••

377/377 FC/378/378 FC
Users Manual
2

Clamp Meter
Before You Start
3
Before You Start
Table 2 is a list of items included with the Product. Use Table 3 to
order additional accessories.
Table 2. Standard Equipment
Item Model Number Description
varies Clamp Meter
i2500-18 iFlex Flexible Current Probe 18 in (48 cm)
TPAK Hanging Kit
AC285 Alligator Clips (one pair, red and black)
TL224 Insulated Test Leads
TP220 Industrial Test Probes
1
2
3
4
5
6

377/377 FC/378/378 FC
Users Manual
4
Table 3. Accessories
Item Model Number Description
C550 Tool Bag
AC87 Heavy-Duty Bus Bar Clip Set (one pair: red and black)
AC89 Heavy-Duty Insulation Piercing Test Clip
LVD1 Volt Light
L206 LED Hat Light
TL75 Hard Point Test Lead Set (one pair: red and black)

Clamp Meter
Before You Start
5
Terms to Know
Use this section to familiarize yourself with these terms that are
unique to this Product.
Field Sense/Non-contact voltage (NCV) measurement. Voltage
measurements by capacitive sensing technology complete
galvanic isolation. This technology uses capacitive sensors for
measuring AC voltages via non-galvanic contact, coupled with a
Hall Effect jaw that allows simultaneous current measurements. It
enables minimizing voltage probes connections, therefore
reducing hazardous situations and saving setup-up time, and
circuit or machine downtime. Fluke-developed icon for Field Sense
is U.
L1-L2-L3. L1, L2, and L3 (or Line 1, Line 2, and Line 3) is a
common naming convention for the wires in three-phase
alternating current (ac) systems. The Clamp features a sequential
line-to-ground measurement that results in a calculated voltage
measurement. This voltage measurement is an indication that the
three-phase system is, or is not, working as expected.
Fluke Connect™. Fluke Connect is a system that wirelessly
connects your Clamp with an app on your smartphone or tablet.
THD. The total harmonic distortion is a measurement of the
harmonic distortion present in a signal and is defined as the ratio
of the sum of the powers of all harmonic components to the power
of the fundamental frequency.
Fluke Connect™ (377 FC/378 FC)
The Clamp supports the Fluke Connect™ Wireless System (may not
be available in all regions). Fluke Connect is a system that wirelessly
connects your Clamp with an app on your smartphone or tablet. The
app shows the measurements and calculations on your smartphone
or tablet display. You can save these measurements, calculations, and
images to Fluke Connect™ Cloud storage and share with your team.
Fluke Connect™ uses low-power 802.15.4 wireless radio
technology to connect the Clamp with an app on your smartphone
or tablet. The wireless radio does not cause interference with
Clamp measurements.
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.
SIMPLIFIED EU DECLARATION OF CONFORMITY
Hereby, Fluke declares that the radio equipment contained inthis
Product is in compliance with Directive 2014/53/EU.
Fluke Connect™ App
The Fluke Connect™ app works with Apple and Android mobile
products. The app is available for download to your smart device
from the Apple App Store and Google Play.
To use Fluke Connect:
1. Turn on the Clamp. See Figure XXX.
2. Push Fto activate the radio on the Clamp. Eshows on the
display.
3. On your smartphone, go to Settings > Bluetooth.
4. Verify that Bluetooth is turned on.
5. Go to the Fluke Connect App and in the list of connected
Fluke tools, select 377 FC/378 FC.

377/377 FC/378/378 FC
Users Manual
6
Battery
XW Warning
To prevent personal injury and for safe operation
of the Product:
• The battery door must be closed and locked
before you operate the Product.
• Remove all probes, test leads, and accessories
before the battery door is opened.
• Replace the batteries when the low battery
indicator shows to prevent incorrect
measurements.
• When batteries are changed, ensure that the
calibration seal in the battery compartment is
not damaged. If damaged, the Product may not
be safe to use. Return the Product to Fluke for
replacement of the seal.
WCaution
To prevent damage to the battery:
• Repair the Product before use if the battery
leaks.
• Do not expose battery to heat sources or high-
temperature environments such as an
unattended vehicle in the sun.
• Always operate in the specified temperature
range.
• Do not incinerate the Product and/or battery.
To install the batteries:
1. Open the battery door. See Figure 1.
2. Insert the batteries.
3. Close the battery door. Make sure the door is firmly closed.
Figure 1. Battery
AA