Hioki CM3281, CM3291 User Manual

CM3281

[FILTER] : Not used
[HOLD]
[AUTO]

CM3291

AC CLAMP METER

Instruction Manual

Dec. 2019 Edition 1
CM3281A961-00 19-12H

Warranty

Warranty malfunctions occurring under conditions of normal use in
conformity with the Instruction Manual and Product Precautionary
Markings will be repaired free of charge. This warranty is valid for a
period of three (3) years from the date of purchase. Please contact
the distributor from which you purchased the product for further
information on warranty provisions.

Introduction

Thank you for purchasing the Hioki CM3281, CM3291 AC Clamp

Meter. To obtain maximum performance from the instrument, please
read this manual rst, and keep it handy for future reference. Be

sure to also read the separate document “Operating Precautions”
before use.

CM3281 Average value measurement RMS conversion model

CM3291 True RMS measurement model

Target audience

This manual has been written for use by individuals who use the
product in question or who teach others to do so. It is assumed that
the reader possesses basic electrical knowledge (equivalent to that
of someone who graduated from the electrical program at a techni­cal high school).

EN

Safety Notes

Symbols affixed to the device

Precaution or hazard (See corresponding topic.)

The instrument can be connected to or disconnected from a
live conductor

The exible sensor can be connected to or disconnected from

live conductors when appropriate protective insulation is used.
The clamp meter and test leads can only be connected to or
disconnected from insulated conductors suited to the voltage
of the conductor under measurement.

DANGER

To avoid electric shock, do not touch the portion
beyond the protective barrier during use.

Do not subject the instrument to any voltages when
the resistance measurement or continuity check
function is selected. Doing so may damage the in­strument and result in bodily injury. To avoid electri­cal accidents, turn off the circuit before measuring it.

WARNING

• To avoid electric shock, short circuits and damage
to the instrument, disconnect the test leads from
the measurement object before switching the ro­tary switch.

• To prevent electric shock, when measuring the

voltage of a power line use a test lead that satises

the following criteria:

• Conforms to safety standards IEC61010 or EN61010

• Of measurement category III or IV

• Its rated voltage is higher than the voltage to be
measured

• The optional test leads for this instrument conform
to the safety standard EN61010. Use a test lead in

accordance with its dened measurement category

and rated voltage.

• To prevent a short circuit accident, be sure to use
the L9208 test leads with the sleeves attached
when performing measurements in the CAT III mea­surement category. (For the measurement catego­ries, see the “Measurement categories” section in
the separate document “Operating Precautions”.)

• If the sleeves are removed during measurement,
stop the measurement.

• Handle and dispose of batteries in accordance with
local regulations.

CAUTION

Do not place foreign objects between the jaw tips (or

exible loop couplings) or insert foreign objects into the
gaps of the jaws (or exible loop couplings). Doing so

may worsen the performances of the sensor or interfere
with clamping action.

• The indicator is displayed when the remaining battery
capacity is low. In this case, the accuracy of the instru­ment is not guaranteed. Replace the battery immediately.

• To avoid battery depletion, set the rotary switch in the

[OFF] position after use. (Even when the automatic

power-saving function is enabled, the instrument con­sumes a small amount of the battery power.)

Inspection Before Measurement

• Before using the instrument, check it and verify that it operates
properly to make sure that it suffered no damage during storage or
transportation.

• If damage is suspected, check the section below before contacting
your authorized Hioki distributor or reseller.

(1) Check the test lead for breaks.

If any, replace it with the new L9208 Test Lead.

(2) Check that the resistance measurement and continu-

ity check operates normally.

If any one of them does not operate normally, send the instru­ment for repair to the your authorized Hioki distributor or
reseller. The instrument may have been subject to a voltage of
greater than 600 V during resistance measurement or continu-

ity check.

(3) Check that the battery weakens.

If it weakens, replace the battery.

Functions

Automatic power-saving function

The instrument automatically turns off the LCD after it is not
operated for 30 minutes.

• To enable the function

• To restore the instrument from a non-displaying state

Set the rotary switch in the [OFF] position and then set the rotary

1

switch in a position other than [OFF].

• To cancel automatic power-saving function

Set the rotary switch in a position other than [OFF] while holding

1

down the HOLD key.
The text [APS] and [OFF] are displayed in turn on the LCD, and
the automatic power-saving function is disabled.

Auto-range function

The instrument automatically selects the most appropriate
measurement range.

The text [AUTO] is displayed on the LCD.

Manual-range function

Sets the measurement range manually.

Set the rotary switch in the [OFF] position and then set the rotary

1

switch in a position other than [OFF] while holding down the

key.

Press the key to switch the measurement range.

2

(Any ranges can be set except for the continuity check.)

Overflow indication

If an input exceeds the measurement range, the text [OF] or [−OF]
is displayed on the LCD.

Parts Names

LCD (with all segments turned on)

: Holds measured value
: Auto-range function

: Low battery warning

: Connection of exible loop

: Continuity check

The instrument screen displays the alphanumeric characters as follows.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

1 2 3 4 5 6 7 8 9 0

AC Clamp Meter

Front

Jaw

Barrier

Operating
grip

LCD

key

HOLD key

(Press to hold the
displayed value.)

Rotary switch

Measurement

terminal

Plug of test lead or

exible sensor

Rear

Battery
cover

Serial number

The 9-digit serial number indicates

the year (rst two digits) and the
month of manufacture (next two

digits). Do not remove this sticker
as the number is important.

Carrying case storage

L9208 Test Lead’s
sleeves (accessory)

L9208 Test Lead
(red, black)

• Instruction Manual

• Download Guide

• Operating Precautions

CT6280 AC Flexible Current Sensor (optional)

Flexible loop

Cap

Cap

(Approx. φ7 mm)

Instruction

plate

Using the attachment

allows the exible

loop to weave through
cables easily.

Attachment

Cap

Measuring Methods

NO

OK

NO

NO

NO

NO

NO

OK

NO

NO

NO

AC Current Measurement [ ]

Measuring current with the instrument

1 2

OK

NO

Measuring current with Model CT6280 AC Flexible
Current Sensor (optional)

Use protective gear

1 2 3

4

5

Cannot measure
current

OK

1 wire

NO

NO

Do not pull the exible loop
with excessive force.

Voltage Measurement

AC Voltage Measurement [

To avoid damage, . . .

Do not bend the

exible loop.

Wire binding band

Do not pack the exible

loop with it bent.

]

1 2 3 4

DC Voltage Measurement [

1 2 3 4

]

OK

NO

Black

(−)

Red

(−)

Red

(+)

Black

(+)

3

Resistance Measurement [ ]

21 3 4

5

Continuity Check [ ]

21 3

4

5

Cleaning

• Measurements are degraded by dirt on the mating surfaces of the
jaw (or exible loop coupling), so keep the surfaces clean by gently

wiping with a soft, dry cloth.

• To clean the instrument, wipe it gently with a soft cloth moistened
with water or mild detergent.

• Wipe the LCD gently with a soft, dry cloth.

Replacing Battery

Necessary items: Phillips screwdriver (No.1) and Coin cell lithium
battery (CR2032)

NO

2

CR2032 (new)

Do not loosen any screws but

OK

Do not turn any one of the 3 screws inside the battery case. Doing
so will cause the instrument to report abnormal measured values.

CALIFORNIA, USA ONLY

This product contains a CR Coin Lithium Battery which contains
Perchlorate Material - special handling may apply.
See www.dtsc.ca.gov/hazardouswaste/perchlorate

Specifications

Function Specifications

Display Maximum count: 4199 counts

Battery indicator
warning voltage

General Specifications

Operating
environment
Operating temperature and humidity

Temperature −25°C to 65°C (−13°F to 149°F)

The mark

2.3 V±0.15 V or less.

Indoors, pollution degree 2, altitude up to 2000 m (6562 ft.)

Ω

(For the 40 M

range: up to 40°C [104°F])

the one securing the cover.

is displayed at a battery voltage of

431

Humidity
(no condensation)

Storage tempera­ture and humidity
Drop-proof Operate after a drop from 1 m on concrete
Standards Safety: EN61010

Power supply Coin cell lithium battery CR2032 ×1

Continuous
operating time

Dimensions

Dimensions (Jaw)
Mass

Product warranty
period
Accessories • Carrying Case

Options The following options are available for the instrument. To

Less than 40°C (104°F): 80% RH or less
At least 40°C (104°F) but less than 45°C (113°F):
60% RH or less
At least 45°C (113°F) but less than 50°C (122°F):
50% RH or less
At least 50°C (122°F) but less than 55°C (131°F):
40% RH or less
At least 55°C (131°F) but less than 60°C (140°F):
30% RH or less
At least 60°C (140°F) but less than 65°C (149°F):
25% RH or less

−25°C to 65°C (−13°F to 149°F),
80% RH or less (no condensation)

EMC: EN61326

Rated power voltage: 3 V DC

Maximum rated power: 15 mVA
CM3281: Approx. 120 hours
CM3291: Approx. 70 hours

(AC current measurement mode, continuous, unloaded,
under conditions of temperature and humidity for guaran­teed accuracy)

• CM3281, CM3291: Approx. 57W×198H×16D mm

(2.24″W × 7.80″H × 0.63″D)

• CT6280: Approx. 42W×65H×18D mm

(1.65″W × 2.56″H × 0.71″D)
(excluding the exible loop and output cable)

Approx. 65W×13D mm (2.56

• CM3281, CM3291: Approx. 103 g (3.6 oz.) (including battery)

• CT6280: Approx. 71 g (2.5 oz.)

CM3281, CM3291, CT6280: 3 years

• L9208 Test lead

• Coin cell lithium battery CR2032 (Installed in the instru-
ment, for LCD)

• Instruction Manual (This document)

• Download Guide

• Operating Precautions (0990A909)

purchase an option, please contact your authorized Hioki
distributor or reseller. Options are subject to change.
Please check Hioki’s website for the latest information.

• CT6280 AC Flexible Current Sensor
(Attachment and C0205 Carrying Case are included)

• L4933 Contact Pin Set
(Can be connected to the tip of the L9208, which comes
with the instrument.)

• L4934 Small Alligator Clip Set
(Can be connected to the tip of the L9208, which comes
with the instrument.)

• L9208 Test Lead

″W × 0.51″D

)

Basic Specifications

Maximum input
current

Maximum input
voltage
Overload
protection
Maximum rated voltage to earth

CM3281,
CM3291 (jaw)/
CT6280
Voltage
measurement
terminal

AC measure­ment method
Display update
rate
Noise rejection
characteristics

Crest factor

Zero-display
range

• CM3281, CM3291 (Jaw): 2000 A AC, continuous (45 Hz
to 66 Hz)

• CT6280 (Flexible loop): 4200 A AC, continuous (50 Hz
to 60 Hz)

6

600 V AC/DC and 3×10

600 V AC/DC (ACV, DCV,

600 V AC (Measurement category III),
300 V AC (Measurement category IV)
(Anticipated transient overvoltage: 6000 V)
600 V AC (Measurement category II),
300 V AC (Measurement category III)

(Anticipated transient overvoltage: 4000 V)

CM3281: Average value measurement RMS conversion model
CM3291: True RMS measurement model

400 ms±25 ms

NMRR DCV −40 dB or more (50 Hz/60 Hz)
CMRR DCV −100 dB or more

(50 Hz/60 Hz, 1 k
ACV −60 dB or more
(50 Hz/60 Hz, 1 kΩ unbalance)

CM3291: For 2500 counts or less, 2.5

Reduces linearly to 1.5 or less at 4200 counts

But, 1.5 or less for 2000 A ACA range

5 counts (AC current measured with jaw or exible loop)

V·Hz or less (ACV, DCV)

Ω

, continuity)

Ω

unbalance)

But, −45 dB or more for 600 V range.

Effects of con­ductor position

Maximum mea­surable conduc­tor diameter
Model CT6280

• CM3281, CM3291

11‑mm‑diameter [22 mm2] cable)

• CT6280: within ±5.0% (At any positions, based on the
center of sensor)

• CM3281, CM3291: φ46 mm or less

• CT6280: φ130 mm or less

Cross-section diameter of sensor cable:
Sensor-tip cap diameter:
Output cable length:

: within ±5.0% (Specied with a

Approx.

Approx.

Approx.

φ7.0 mm

800 mm

φ5.0 mm

Accuracy Specifications

rdg (reading or displayed value):The value currently being measured and

indicated on the measuring instrument.

dgt (resolution):The smallest displayable unit on a digital measuring instru-

ment, i.e., the input value that causes the digital display to show a “1” as

the least‑signicant digit.

Conditions of guaranteed accuracy

• Guaranteed accuracy period: 1 year (Number of jaw and exible loop open/
close cycles: 10,000 or less)

• Guaranteed accuracy period after adjustment made by Hioki: 1 year

• Temperature and humidity for guaranteed accuracy: 23°C±5°C (73°F±9°F),

80% RH or less

• Supply voltage for guaranteed accuracy: The mark is not displayed.

• Temperature characteristic: Measurement accuracy × 0.1/°C is added

(excluding 23°C±5°C)

• AC waveform: sine wave

AC Current Measured With Jaw (CM3281)

Range Accuracy range

42.00 A 4.00 A to 41.99 A

2000 A 100 A to 1999 A

AC Current Measured With Jaw (CM3291)

Range Accuracy range

42.00 A 4.00 A to 41.99 A

420.0 A 40.0 A to 419.9 A

2000 A 100 A to 1999 A

Accuracy is not dened for currents of 3×10

AC Current Measured With Flexible loop (CM3281)

Range Accuracy range

420.0 A 40.0 A to 419.9 A
4200 A 400 A to 4199 A

AC Current Measured With Flexible loop (CM3291)

Range Accuracy range

420.0 A 40.0 A to 419.9 A ±3.5% rdg
4200 A 400 A to 4199 A

AC Voltage

Range Accuracy range

0.400 V

to

4.200 V

42.00 V 4.00 V to 41.99 V 10 M

420.0 V 40.0 V to 419.9 V 10 M
600 V 400 V to 600 V 10 M

DC Voltage

Range Accuracy range Accuracy Input impedance

420.0 mV 40.0 mV to 419.9 mV

4.200 V 0.400 V to 4.199 V

42.00 V 4.00 V to 41.99 V 10 M

420.0 V 40.0 V to 419.9 V 10 M
600 V 400 V to 600 V 10 M

Resistance

Range Accuracy range Accuracy

Ω

420.0

Ω

4.200 k

Ω

42.00 k

Ω

420.0 k

4.200 MΩ0.400 MΩ to

Ω

42.00 M

Continuity Check

Range Accuracy

Ω

420.0

*1:

Includes accuracy of CT6280 AC Flexible Current Sensor, ±1.0% rdg

*2: Accuracy is not dened for a current of 1000 A or more or that of

5×105 A · Hz or more.

4.199 V

40.0 Ω to 419.9

0.400 kΩ to 4.199 k

4.00 kΩ to 41.99 k

40.0 kΩ to 419.9 k

4.199 MΩ±5.0% rdg ±4 dgt

4.00 MΩ to 41.99 M

±2.0% rdg ±4 dgt

Accuracy

50 Hz ≤ f ≤ 60 Hz

±1.5% rdg ±5 dgt420.0 A 40.0 A to 419.9 A

Accuracy

40 Hz ≤ f <
45 Hz

±2.0% rdg

±5 dgt

5

Accuracy

50 Hz ≤ f ≤ 60 Hz

±3.0% rdg ±5 dgt *

Accuracy

40 Hz ≤ f <
45 Hz

1, *2

±5 dgt *

Accuracy

45 Hz ≤ f ≤

66 Hz

±1.8% rdg

±7 dgt

±2.5% rdg

±5 dgt

±1.0% rdg

±3 dgt

Ω

Ω

±2.0% rdg ±4 dgt

Ω
Ω

Ω

±10.0% rdg ±4 dgt

Threshold for
buzzer sound

Ω

50

45 Hz ≤ f ≤

66 Hz

±1.5% rdg

±5 dgt

A · Hz or more.

1

45 Hz ≤ f ≤

66 Hz

±3.0% rdg
±5 dgt *

66 Hz < f ≤

500 Hz

±2.3% rdg

±8 dgt

±40 Ω or less 3.4 V or less

1

100 M

11 M

66 Hz < f ≤

1 kHz

±2.0% rdg

±5 dgt

66 Hz < f ≤

1 kHz

±3.5% rdg

1, *2

±5 dgt *

Input
impedance

Ω

±5%

11 M

Ω

±5%

Ω

±5%

Ω

±5%

Ω

or more

Ω

±5%

Ω

±5%

Ω

±5%

Ω

±5%

Open-circuit
voltage

3.4 V or less

Open-circuit
voltage