Fluke 374 Use and care manual

December 2010
© 2010 Fluke Corporation. All rights reserved. Specifications are subject to change without notice.
All product names are trademarks of their respective companies.
374/375/376
Clamp Meter
Calibration Manual

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.
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
To register your product online, visit register.fluke.com

i
Table of Contents
Title Page
Introduction........................................................................................................ 1
Contact Fluke..................................................................................................... 1
Safety Information ............................................................................................. 2
The Meter........................................................................................................... 5
Specifications..................................................................................................... 5
Electrical Specifications ................................................................................ 5
Mechanical Specifications............................................................................. 8
Environmental Specifications........................................................................ 8
Performance Tests.............................................................................................. 9
Calibration Adjustment...................................................................................... 10
Required Equipment...................................................................................... 10
Adjustment Procedure ................................................................................... 11
Maintenance....................................................................................................... 15
Clean the Product .......................................................................................... 15
Battery Replacement ..................................................................................... 15
User Replaceable Parts ...................................................................................... 16

374/375/376
Calibration Manual
ii

iii
List of Tables
Table Title Page
1. Symbols.................................................................................................................. 4
2. Performance Tests.................................................................................................. 9
3. Required Equipment............................................................................................... 10
4. Adjustment Procedure............................................................................................ 13
5. User Replaceable Parts........................................................................................... 16

374/375/376
Calibration Manual
iv

v
List of Figures
Figure Title Page
1. The Meter ............................................................................................................... 5
2. Position Sensitivity................................................................................................. 6
3. Calibration Activation............................................................................................ 11
4. Current Calibration Setup....................................................................................... 12
5. Changing the Batteries ........................................................................................... 16

374/375/376
Calibration Manual
vi

1
Introduction
XWWarning
Read "Safety Information" before you use the Product.
This manual explains the Calibration Adjustment for the 374, 375, and 376 Clamp Meters
(the Product). Please see the 374/375/376 Users Manual for usage information.
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]
•Singapore: [phone]
•China: [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.

374/375/376
Calibration Manual
2
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 Product and in this manual are explained in Table 1.
XWWarning
To prevent possible electrical shock, fire, or personal injury:
•Use the product only as specified, or the protection supplied
by the Product can be compromised.
•Examine the case before you use the Product. Look for
cracks or missing plastic. Carefully look at the insulation
around the terminals.
•Do not measure current while the test leads are in the input
jacks.
•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.
•Do not use test leads if they are damaged. Examine the test
leads for damaged insulation, exposed metal, or if the wear
indicator shows. Check test lead continuity.
•Do not use the Product if it operates incorrectly.
•Do not use the Product around explosive gas, vapor, or in
damp or wet environments.
•Use only type AA batteries, properly installed in the Product
case, to power the Product.
•Hold the Product behind the tactile barrier. See Figure 1, .
•Replace the batteries when the low battery indicator ()
shows to prevent incorrect measurements.
•Use only specified replacement parts.
•Have an approved technician repair the Product.
•Do not touch voltages >30 V ac rms, 42 V ac peak, or 60 V
dc.
•Do not apply more than the rated voltage, between the
terminals or between each terminal and earth ground.
•Keep fingers behind the finger guards on the probes.
•Connect the common test lead before the live test lead and
remove the live test lead before the common test lead.
•Do not work alone.

Clamp Meter
Safety Information
3
•Use caution around bare conductors or bus bars. To prevent
electrical shock, do not touch the conductor.
•Comply with local and national safety codes. Use personal
protective equipment (approved rubber gloves, face
protection, and flame-resistant clothes) to prevent shock
and arc blast injury where hazardous live conductors are
exposed.
•Disconnect power and discharge all high-voltage capacitors
before you measure resistance or continuity.
•For the 374 and 375, do not measure ac/dc current in
circuits carrying more than 1000 V or 600 A with the Product
Jaw.
•For the 376, do not measure ac/dc current in circuits
carrying more than 1000 V or 1000 A with the Product Jaw.
•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.
•Do not use the flexible current sensor if the inner
contrasting insulation color is showing.
•Take special care during fitting and removal of the Flexible
Current Probe. De-energize the installation under test or
wear suitable protective clothing.
•Do not operate the product with covers removed or the case
open. Hazardous voltage exposure is possible.
•When batteries are changed, ensure that the calibration seal
in the battery compartment is not damaged. If damaged, the
Product may not be safe for use. Return the Product to
Fluke for replacement of the seal.
•Do not exceed the Measurement Category (CAT) rating of
the lowest rated individual component of a product, probe,
or accessory.
•Measure a known voltage first to make sure that the Product
operates correctly.
WCaution
To prevent possible damage to the product or to equipment
under test:
•Use the correct terminals, function, and range for
measurements.
•Clean the case and accessories with a damp cloth and mild
detergent only. Do not use abrasives or solvents.

374/375/376
Calibration Manual
4
Table 1. Symbols
Symbol Meaning Symbol Meaning
BAC (Alternating Current) JEarth ground
FDC (Direct Current) ~
Do not dispose of this product as
unsorted municipal waste. Go to
Fluke’s website for recycling
information.
XHazardous voltage PConforms to European Union
directives.
WRisk of Danger. Important information. See
Manual. )Conforms to relevant North American Safety Standards.
Battery. Low battery when shown on
display. TDouble insulated
®Examined and licensed by TÜV Product
Services. ;Conforms to relevant Australian standards.
,Application around and removal from
HAZARDOUS LIVE conductors is
permitted.
-Do not apply to or remove from
HAZARDOUS LIVE conductors.
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.
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.

Clamp Meter
The Meter
5
The Meter
Clamp Meter
fig01.eps
Figure 1. The Meter
Specifications
Electrical Specifications
AC Current via Jaw
Range
374 and 375 ......................................600.0 A
376.....................................................999.9 A
Resolution...............................................0.1 A
Accuracy .................................................2 % ±5 digits (10-100 Hz)
2.5 % ±5 digits (100-500 Hz)
Crest Factor (50/60 Hz) ..........................3 @ 500 A (375 and 376 only)
2.5 @ 600 A
1.42 @1000 A (376 only)
Add 2 % for C.F. > 2
AC Current via Flexible Current Probe
Range ....................................................2500 A
Resolution
374 and 375 ........................................ 0.1 A (≤1000 A)
1 A (≤2500 A)
376 ...................................................... 0.1 A (≤999.9 A)
1 A (≤2500 A)
Accuracy .................................................3 % ±5 digits (5 – 500 Hz)
Crest Factor (50/60Hz) ...........................3.0 at 1100 A (375 and 376 only)
2.5 at 1400 A
1.42 at 2500 A
Add 2 % for C.F. > 2

374/375/376
Calibration Manual
6
Position Sensitivity
A
B
C
ghn12.eps
Figure 2. Position Sensitivity
Distance from
Optimum i2500-10 Flex i2500-18 Flex Error
A 0.5 in (12.7 mm) 1.4 in (35.6 mm) ±0.5 %
B 0.8 in (20.3 mm) 2.0 in (50.8 mm) ±1.0 %
C 1.4 in (35.6 mm) 2.5 in (63.5 mm) ±2.0 %
Measurement uncertainty assumes centralized primary conductor at optimum position, no external
electrical or magnetic field, and within operating temperature range.
DC Current
Range
374 and 375 ......................................600.0 A
376.....................................................999.9 A
Resolution...............................................0.1 A
Accuracy .................................................2 % ±5 digits
AC Voltage
Range
374 and 375 ........................................ 600.0 V
376 ......................................................1000 V
Resolution
374 and 375 ........................................ 0.1 V
376 ...................................................... 0.1 V (≤600.0 V)
1 V (≤1000 V)
Accuracy .................................................1.5 % ±5 digits (20 – 500 Hz)

Clamp Meter
Specifications
7
DC Voltage
Range
374 and 375 ........................................ 600.0 V
376 ...................................................... 1000 V
Resolution
374 and 375 ........................................ 0.1 V
376 ...................................................... 0.1 V (≤600.0 V)
1 V (≤1000 V)
Accuracy .................................................1 % ±5 digits
mV dc
Range
375 and 376.......................................500.0 mV
Resolution...............................................0.1 mV
Accuracy .................................................1 % ±5 digits
Frequency via Jaw
Range
375 and 376.......................................5.0 - 500.0 Hz
Resolution...............................................0.1 Hz
Accuracy .................................................0.5 % ±5 digits
Trigger Level...........................................5 – 10 Hz, ≥10 A
10 – 100 Hz, ≥5 A
100 – 500 Hz, ≥10 A
Frequency via Flexible Current Probe
Range
375 and 376 ...................................... 5.0 – 500.0 Hz
Resolution.............................................. 0.1 Hz
Accuracy ................................................ 0.5 % ±5 digits
Trigger Level.......................................... 5 – 20 Hz, ≥25 A
20 – 100 Hz, ≥20 A
100 – 500 Hz, ≥25 A
Resistance
Range
374.....................................................6000 Ω
375 and 376.......................................60 kΩ
Resolution
374.....................................................0.1 Ω(≤600 Ω)
1 Ω(≤6000 Ω)
375 and 376.......................................0.1 Ω(≤600 Ω)
1 Ω(≤6000 Ω)
10 Ω(≤60 kΩ)
Accuracy .................................................1 % ±5 digits
Capacitance
Range .................................................... 1000 μF
Resolution.............................................. 0.1 μF (≤100 μF)
1 μF (≤1000 μF)
Accuracy .................................................1 % ±4 digits

374/375/376
Calibration Manual
8
Mechanical Specifications
Size (L x W x H) ..................................... 246 mm x 83 m x 43 mm
Weight.....................................................388 g
Jaw Opening...........................................34 mm
Flexible Current Probe Diameter ............ 7.5 mm
Flexible Current Probe Cable Length
(head to electronics connector) ..............1.8 m
Environmental Specifications
Operating Temperature........................... -10 °C – +50 °C
Storage Temp .........................................-40 °C – +60 °C
Operating Humidity .................................Non condensing (< 10 °C)
≤90 % RH (at 10 °C – 30 °C)
≤75 % RH (at 30 °C – 40 °C)
≤45 % RH (at 40 °C – 50 °C)
Operating Altitude ...................................3000 meters
Storage Altitude ......................................12,000 meters
EMC........................................................EN 61326-1:2006
Temperature Coefficients........................Add 0.1 x specified accuracy for each degree C above
28 °C or below 18 °C
Safety Specifications
Safety Compliance.................................. CAN/CSA-C22.2 No. 61010-1-04
ANSI/UL 61010-1:2004
ANSI/ISA-61010-1 (82.02.01):2004
EN/IEC 61010-1:2001 to
1000V Measurement Category (CAT) III
600V Measurement Category (CAT) IV
Pollution Degree 2
EN/IEC 61010-2-032:2002
EN/IEC 61010-031:2002+A1:2008
P
Agency Approvals...................................),;,®
Batteries..................................................2 AA, NEDA 15A, IEC LR6

Clamp Meter
Performance Tests
9
Performance Tests
XWWarning
To prevent possible electrical shock, fire, or personal injury,
do not perform the performance test procedures unless the
Product is fully assembled.
The following performance tests verify the complete operation of the Product and check
the accuracy of each function against the Product’s specifications. See Table 2. If the
Product fails any part of the test, calibration adjustment and/or repair is indicated. See
“Calibration Adjustment”.
Table 2. Performance Tests
Meter Reading Limit
Test
(Switch
Position)
Calibrator
Output 374 375 376
Low High
10 V @ 50 Hz X X X 9.7 V 10.3 V
500 V @ 50 Hz X X X 496.0 V 504.0 V
900 V @ 50 Hz - - X 893.0 V 907.0 V
K
AC Volts
500 V @ 500 Hz X X X 496.0 V 504.0 V
-500 V X X X -503.0 V -497.0 V
10 V X X X 9.7 V 10.3 V
500 V X X X 497.0 V 503.0 V
900 V - - X 895.0 V 905.0 V
-250 mV - X X -251.5 V -248.5 V
50 mV - X X 49.5 V 50.5 V
250 mV - X X 248.5 V 251.5 V
L
DC Volts
450 mV - X X 447.5 V 452.5 V
60 ΩX X X 59.5 Ω60.5 Ω
300 ΩX X X 298.2 Ω301.8 Ω
540 ΩX X X 537.0 Ω543.0 Ω
3000 ΩX X X 2982 Ω3018 Ω
5400 ΩX X X 5370 Ω5430 Ω
30K Ω- X X 29.82 KΩ30.18 KΩ

Ohms
54K Ω- X X 53.70 KΩ54.30 Ω
10 μF X X X 9.8 μF 10.2 μF
500 μF X X X 496.0 μF 504.0 μF

Capacitance
900 μF X X X 894.0 μF 906.0 μF

374/375/376
Calibration Manual
10
Table 2. Performance Tests (cont.)
Meter Reading Limit
Test
(Switch
Position)
Calibrator
Output 374 375 376
Low High
0.2 A @ 50 Hz X X X 9.7 A 10.3 A
10 A @ 50 Hz X X X 495.0 A 505.0 A
18 A @ 5 0Hz - - X 891.0 A 909.0 A
?
AC Amps
(with 50-
turn Coil) 6 A @ 440 Hz X X X 296.0 A 304.0 A
0.2 A X X X 9.7 A 10.3 A
10 A X X X 495.0 A 505.0 A

DC Amps
(with 50-
turn Coil)
18 A - - X 891.0 A 909.0 A
3 mV @ 50 Hz X X X 98.2 A 101.8 A
30 mV @ 50 Hz X X X 982 A 1018 A
60 mV @ 50 Hz X X X 1967 A 2033 A
75 mV @ 50 Hz X X X 2460 A 2540 A

iFlex
Current
Probe
(with
Simulation) 750 mV @ 500 Hz X X X 2460 A 2540 A
0.2 A @ 50 Hz X X X 9.6 A 10.4 A
10 A @ 50 Hz X X X 493.0 A 507.0 A
18 A @ 50 Hz X X X 887.0 A 913.0 A

iFlex
Current
Probe
(with 50-
turn Coil)
6 A @ 440 Hz X X X 295.2 A 304.8 A
Calibration Adjustment
Required Equipment
The equipment listed in Table 3 is required for calibration adjustment.
Table 3. Required Equipment
Equipment Required Characteristics Recommended Model
Calibrator 4.5-digit resolution Fluke 55xxA Calibrator
Wired coil 50 turns 5500A/COIL
Test Lead for iFlex PN 666602
Test Lead for other PN 2070140
Power Supply +3.0 V Common power supply or a 2 x
AA or AAA battery container

Clamp Meter
Calibration Adjustment
11
Adjustment Procedure
To adjust Product calibration:
1. Turn the Product over to access the battery compartment door screw.
2. Use a flat-head screwdriver to loosen the battery compartment door screw and lift off
the battery compartment door. See Figure 5.
3. Remove the calibration sticker.
4. Connect the Power Supply to the Product battery terminals.
5. Turn the Product ON.
6. Use a small jumper to short the two pads together under the calibration sticker. This
will put the Product into calibration mode. See Figure 3.
Short circuit these two pads for
1 s to access to Calibration mode.
ghn51.eps
Figure 3. Calibration Activation
7. Turn the rotary switch to select the function to be calibrated.
8. Apply the required output from the source to the Product. See Table 4.
9. Wait until each applied output stabilizes.
10. Push to confirm the value and move to the next step in the Adjustment
Procedure.
For Current calibration, see Figure 4 for connections.

374/375/376
Calibration Manual
12
1
4
7
/
+
STB
Y
5522A CALIBRATOR
HI
LO
TRIG
GUARD
TC
20A
NORMAL AUX SCOPE
OUT
V, , ,RTD A, -SENSE, AUX V
20VPK MAX
20VPK MAX
ghn50.eps
Figure 4. Current Calibration Setup
The calibration adjustment is complete.
When the adjustment is complete:
1. Remove the Power Supply.
2. Replace the batteries.
3. Reattach the battery compartment door.
4. Tighten the battery compartment door screw.