Hioki 3255-50 Instruction Manual

INSTRUCTION MANUAL

3255-50

DIGITAL HiTESTER

i

Contents

Contents

Introduction...............................................................1

Inspection..................................................................1

Safety Notes .............................................................2

Usage Notes.............................................................6

Chapter 1 Overview 13

1.1 Product Overview....................... ...... ..... ....13

1.2 Features....................................................13

1.3 Parts Names and Functions......................14

Chapter 2 Measurement Procedures 17

2.1 Connection................................................17

2.2 Voltage Measurement...............................19

2.3 Current Measurement ...............................21

2.4 Resistance Measurement..........................24

2.5 Continuity Check .......................................25

2.6 Diode Check..............................................26

Chapter 3 Additional Functions 27

3.1 Auto Range Function and Manual Range

Function.....................................................27

3.2 HOLD AUTO Function...............................29

3.3 Overflow Warning Function.......................30

3.4 Auto Power Save Function........................31

Contents

ii

Chapter 4 Specifications 33

4.1 General Specifications..............................33

4.2 Accuracy ................................................... 37

Chapter 5 Maintenace and Service 39

5.1 Replacing the Batteries and Fuses........... 39

5.2 Cleaning and Storage............................... 42

5.3 Service......................................................43

1

Introduction

Thank you for purchasing the HIOKI "3255-50
DIGITAL HiTESTER." To obtain maximum perfor­mance from the product, please read th is manual
first, and keep it handy for future reference.

Inspection

When you receive the product, inspect it carefully
to ensure that no damage occurred during ship­ping. In particular, check the accessories, panel
switches, and connectors. If damage is evident, or
if it fails to operate according to the specifications,
contact your dealer or Hioki representative.

Introduction

Accessories

• 9207-10 TEST LEAD .....................................1

• Instruction Manual..........................................1

• R03 Manganese battery.................................2

(Supplied with this product, for monitor)

• 9371 CARRYING CASE ................................1

Options

• 9010 CLAMP ON PROBE

• 9018 CLAMP ON PROBE

Safety Notes

2

Safety Notes

This manual contains information and warnings
essential for safe operation of the product and for
maintaining it in safe operating condition. Before
using the product, be sure to carefully read the fol­lowing safety notes.

This product is designed to conform to IEC
61010 Safety Standards, and has been thor­oughly tested for safety prior to shipment.
However, mishandling during use could
result in injury or death, as well as damage to
the product. Be certain that you understand
the instructions and precautions in the man­ual before use. We disclaim any responsibil­ity for accidents or injuries not resulting
directly from product defects.

3

Safety Symbols

In the manual, the symbol indicates particu­larly important information that the user should
read before using the product.
The symbol printed on the product indicates
that the user should refer to a corresponding topic
in the manual (marked with the symbol) before
using the relevant function.

Indicates that dangerous voltage may be present
at this terminal.

Indicates a double-insulated device.

Indicates a grounding terminal.
Indicates DC (Direct Current).

Safety Notes

Symbols

Indicates AC (Alternating Current).
Indicates DC (Direct Current) or AC (Alternating

Current).

The following symbols in this manual indicate the
relative importance of cautions and warnings.

Indicates that incorrect operation presents an ex­treme hazard that could result in serious injury or
death to the user.

Indicates that incorrect operation presents a sig­nificant hazard that could result in serious injury or
death to the user.

Indicates that incorrect operation presents a pos­sibility of injury to the user or damage to the prod­uct.

Advisory items related to performance or correct
operation of the product.

Safety Notes

4

Other Symbols

Indicates the prohibited action

Accuracy

We define measurement tolerances in terms of f.s.
(full scale), rdg. (reading) and dgt. (digit) values,
with the following meanings:

f.s.

rdg.

dgt.

(maximum display value or scale length)
The maximum displayable value or the full length
of the scale. This is usually the maximum value of
the currently selected range.

(reading or displayed value)
The value currently being measured and indicated
on the measuring product.

(resolution)
The smallest displayable unit on a digital measur­ing product, i.e., the input value that causes the
digital display to show a "1".

5

Safety Notes

Measurement categories (Overvoltage categories)

This product conforms to the safety requirements for CAT III
600V, CAT II 1000V measurement products.
To ensure safe operation of measurement products, IEC
61010 establishes safety standards for various electrical envi­ronments, categorized as CAT I to CAT IV, and called mea­surement categories. These are defined as follows.

CAT I

trical outlet through a transformer or similar device.

CAT II

an AC electrical outlet by a power cord (portable tools, house­hold appliances, etc.)

CAT III

installations) connected directly to the distribution panel, and
feeders from the distribution panel to outlets.

CAT IV

entrance, and to the power meter and primary overcurrent
protection device (distribution panel).
Higher-numbered categories correspond to electrical environ­ments with greater momentary energy, so a measurement

: Secondary electrical circuits connect ed to an AC elec-

: Primary electrical circuits in equipment connected to

: Primary electrical circuits of heavy equipment (fixed

: The circuit from the service drop to the service

product designed for CAT III environments can endure
greater momentary energy than one designed for CAT II.
Using a measurement product in an environment designated
with a higher-numbered category than that for which the prod­uct is rated could result in a severe accident, and must be
carefully avoided.
Never use a CAT I measuring product in CAT II, III, or IV envi­ronments.
The measurement categories comply with the Overvoltage
Categories of the IEC60664 Standards.

Usage Notes

6

Usage Notes

Follow these precautions to ensure safe operation
and to obtain the full benefits of the various func­tions.

Inspection before Use

• Before using the product the first time, verify that it
operates normally to ensure that the no damage
occurred during storage or shipping. If you find any
damage, contact your dealer or Hioki representa­tive.

• Before using the product, make sure that the insu­lation on the test leads is undamaged and that no
bare conductors are improperly exposed. Using
the product under such conditions could result in
electrocution. Replace the test leads with the
specified Hioki Model 9207-10.

Inst a llat ion, Ope ratin g Environm ent, and Handli ng

• To avoid electric shock, do not allow the

product to get wet, and do not use it when
your hands are wet.

• Do not use the product where it may be

exposed to corrosive or combustible
gases. The product may be damaged or
cause an explosion.

7

Usage Notes

Observe the following to avoid damage to the
product.

• Installation and Operating Environment
Between 0°C and 40°C; 80% RH or less;
indoors only. Howev er, it can be safely operated
at as low as -10°C.

• Do not store or use the product where it could
be exposed to direct sunlight, high tem perature
or humidity, or condensation.
Under such conditions, the product may be
damaged and insulation may deteriorate so that
it no longer meets specifications.

• Although this product is designed to resist the
ingress of dust and water, it is not entirely water­or dust-proof, so to avoid shoc k or damage, do
not use it in a wet or dusty environment.

The protection rating for the enclosure of this
device (based on EN60529) is *IP54.

• Do not use the product near a device that gener­ates a strong electromagnetic field or electro­static charge, as these may cause erroneous
measurements.

• To avoid damage to the product , protect it from
vibration or shock during transport and handling,
and be especially careful to avoid dropping.

*IP54 This indicates the degree of protection provided by

the enclosure of the device against use in hazard­ous locations, entry of solid foreign objects, and
the ingress of water.

5: Protected against access to hazardous parts with

wire measuring 1.0 mm in diameter. Dust-proof
type (The penetration of dust cannot be prevented
completely, but quantities of dust that may hinder
the stated operation of equipment or safety cannot
penetrate the enclosure.)

4: The equipment inside the enclosure is protected

against the harmful effects of water splashed
against the enclosure from any direction.

Usage Notes

8

• Adjustments and repairs should be made only
by technically qualified personnel.

• If the protective functions of the product are
damaged, either remove it from s ervice or mark
it clearly so that others do not use it inadvert­ently.

• To avoid corrosion from battery leakage, remove
the batteries from the product if it is to be stored
for a long time.

• Accurate measurement may be impossible in the

presence of strong magnetic fields, such as near
transformers and high-current conductors, or in
the presence of strong electromagnetic fields
such as near radio transmitters.

• To avoid battery depletion, turn the function

selector OFF after use (the Auto Power Save
feature consumes a small amount of current).

• The indicator appears when ba ttery voltage

becomes low. Replace the batteries as soon as
possible.

Handling the Cables

• The ends of the test leads are sharp. Be careful
to avoid injury.

• To avoid damaging the cables, do not bend or
pull the cables.

• Avoid stepping on or pinching the cable, which
could damage the cable insulation.

9

Connection and Measurement

For other precautions and details, see explana­tions of the measurement procedures.

Use only the specified test lead or clamp-on probe.
Using a non-specified cable may result in incorrect
measurements due to poor connection or other
reasons.

When measuring a breaker

This product should only be connected to the
secondary side of a breaker, so the breaker
can prevent an accident if a short circuit
occurs. Connections should never be made

Usage Notes

to the primary side of a breaker, because
unrestricted current flow could cause a seri­ous accident if a short circuit occurs.

Voltage Measurem ent

• The maximum input voltage is 1000
VDC,1000 Vrms(sin), or 10

ing to measure voltage in excess of the
maximum input could destroy the product
and result in personal injury or de ath.

• The maximum rated voltage between input
terminals and the ground is as follows;
(CAT II) DC 1000 V, AC1000 Vrms (sin) or

10

(CAT III) DC 600 V, AC600 Vrms (sin) or

10

7

V•Hz

7

V•Hz

7

V•Hz. Attempt-

Attempting to measure voltages exceeding
this level with respect to ground could
damage the product and result in personal
injury.

Usage Notes

10

Resistance Measurement, Checking the
Continuity or Diode

Never apply voltage to test leads when the
Resistance, Continuity or Diode Check func­tions are selected. Doing so may damage
the product and result in personal injury.
To avoid electrical accidents, remove power
from the circuit before measuring.

Current Measurement

(When using the optional Clamp-on Probe)

Connect the Clamp-on probe to the product
first, and then to the active lines to be mea­sured.
Observe the following to avoid electric shock
and short circui t s.

• Never attach the clamp-on probe to a cir­cuit that operates at more than 600 V, or
over bare conductors.

• When the Clamp-on probe is opened, do
not allow the metal part of the clamp to
touch any exposed metal, or to short
between two lines.

To avoid electric shock when measuring live
lines, wear appropriate protective gear, such
as insulated rubber gloves, boots and a
safety helmet.

11

Usage Notes

• To prevent damage to the product and Clamp­on probe, never connect or disconnect a sensor

while the power is on.

• Be careful to avoid dropping the Clamp-on
probe or otherwise subjecting them to mechani-

cal shock, which could damage the m ating sur­faces of the core and adversely affect
measurement.

• Keep the clamp jaws and core slits free from for­eign objects, which could interfere with clamping
action.

Usage Notes

12

13

1.1 Product Ov e r view

Overview Chapter 1

1.1 Product Overview

This measurement product is a multi-functional
digital multimeter capable of measuring DC and
AC voltages, AC currents, and the resistance, and
checking the diode and continuity.

1.2 Features

Compliance with CE marking requirements

The measurement product is designed to comply
with the international safety standard (IEC61010)
and EMC standards.

Handy and safe digital multimeter (DMM) with
protections against accidents

• No need to replace a test lead; two input termi-

nals are provided

• A fuse and protective resist or between input ter-

minals prevent an accident caused by a short cir­cuit.

• The dustproof and waterproof structure pr events

dust and moisture from entering the product
(IP54).

Current measurement (AC) using a Clamp-on
probe

Displays the measured voltage output of an
optional Clamp-on probe as a current v alue using
a scaling function.

1.3 Parts Names and Functions

14

t

t

1.3 Parts Names and Functions

LCD Display

SHIFT Button

RANGE Button

(page 15)

(page 15)

(page 15)

Selects functions

V, mV

CLAMPCurrent measuremen

+ Terminal

Tu rns the power on/off

Red

Connect the 9207-10 TEST LEAD
or optional Clamp-on probes.
Connection method: (page 17)

COM Terminal

Black

When the switch is rotated
clockwise from the OFF posi­tion, the power is turned on.

Function Selector

Voltage measuremen

Resistance measure­ment

Continuity checking
Diode checking

15

1.3 Parts Names and Functions

k

-

it

s

-

-

it

I
f
B

f
I

D
f

I
A
c
f

P
i

t:

t

d

-

-

LCD Display

Indicates Auto Power Save is enable

Indicates Autoranging

function

ndicates

HOLD AUTO

unction is enable.

links when on standby

Indicates diode check function

Indicates continuity chec
function

Indicates current mea
surement function

or a trigger

ndicates

C voltage

unction
ndicates

C voltage/

urrent

unction

olarity

ndicator

Decimal point

Indicates low battery voltage

Current measurement un

Lights up when the voltage drops below t he bat­tery accuracy guarantee voltage (2.3±0.15 V)

Clamp-on
probe range
(7-range)

Resistance
and continu
ity check
units

Voltage mea
surement un

Buttons

SHIFT button

• Selects DC/AC ( )
(Voltage measurement [V,mV])

• Selects function; Continuity
check [ ]/ Diode check [ ]/
Resistance measurement [ ]

• Turns the HOLD AUTO func-

*1

tion on/off

• Cancels the Auto Power Save
function

To reset from the Auto Power
Save state, turn off the power
and turn it on again.

(page 29)

*2

(page 31)

RANGE button

• Voltage measurement,
resistance measuremen
Changes the manual

range and auto range
Selects range (manual
range only).

*1

• Current measurement:
Selects the range of the
Clamp-on probe.

*1: Press the button for at leas

1 second.

*2:Turn on the power while

pressing the button, and hol
the button down until a beep
ing sound is generated (pow
er-on option).

.

1.3 Parts Names and Functions

16

17

Measurement

p
d

to

k

2.1 Connection

Procedures

Observe the following precautions to avoid
electric shock.

• Always verify the appropriate setting of the
function selector before connecting the
test leads.

• Disconnect the test leads from the mea­surement object before switching the func­tion selector.

2.1 Connection

Chapter 2

Voltage measurement/ Resistance measurement/
Continuity check/ Diode check

Safety cap

9207-10
TEST LEAD

1. Remove the protective ca

from the test lead supplie
with the product.

2. Connec t the red test lead

terminal +, and the blac
test lead to terminal COM.

Connect the test lead to the

Red

9207-10 TEST LEAD

Black

terminals securely.

2.1 Connection

18

e

,

al

Current measurement

To perform measurement, an optional Clamp-on probe is
required.

Connect the red plug of th
Clamp-on probe to terminal +
and the black plug to termin

COM.

Connect the plug to the ter­minals securely.

Red

Clamp-on probe

Black

19

2.2 Voltage Measurement

2.2 Voltage Measurement

• The maximum input voltage is 1000
VDC,1000 Vrms(sin), or 10

ing to measure voltage in excess of the
maximum input could destroy the product
and result in personal injury or de ath.

• The maximum rated voltage between input
terminals and the ground is as follows;
(CAT II) DC 1000 V, AC1000 Vrms (sin) or

7

V•Hz

10

(CAT III) DC 600 V, AC600 Vrms (sin) or

7

V•Hz

10

7

V•Hz. Attempt-

Attempting to measure voltages exceeding
this level with respect to ground could
damage the product and result in personal
injury.

• To avoid electrical shock, be careful to
avoid shorting live lines with the test leads.

• For safety, test lead connections must
always be made at the secondary s ide of a
circuit breaker.

The indicated value may vary due to the existence
of induced voltage under no-power conditions.
However, this is not a problem.

2.2 Voltage Measurement

20

n

r
r

f

t-

V

e

s

s

t

e

V measurement

AC Volt age

Measurement

Example

mV measurement

DC Volt age

Measurement

1. Move the functio

selector to the V o
mV position ("V" o

"mV" lights up,
lights up).
If you are not sure o
the approximate vol
age level, select
first.

2. When DC voltag

measurement, pres
the SHIFT button.

( lights up)

3. Connect the test lead

to the measuremen
object, and read th
indicated value.

Black

Red

Selecting the manual range ...
Reselecting the auto range

Holding the me asur ed
value

Appearance of O.F

(page 29).................

...............

....

Example

Black

Red

Press RANGE("AUTO" is turned off)
Press RANGE (for at least 1 second)

("AUTO" lights up)
Press SHIFT (for at least 1 second)→

Measurement
Move the test leads away from the mea­surement objec t.

The measured value exceeds maximum
display counts
420-V range: display up to 4199
1000-V range: display up to 1099

→Intermittent sound→

21

2.3 Current Measurement

2.3 Current Measurement

To perform measurement, an optional Clamp-on
probe is required.

Connect the Clamp-on probes to the product
first, and then to the active lines to be mea­sured. Obse rve the followin g to av oid elec tri c
shock and short circuits.

• To avoid short circuits and potentially life­threatening hazards, never attach the

Clamp-on probe to a circuit that operates
at more than 600 V, or over bare conduc­tors.

• Clamp-on probe should only be connected
to the secondary side of a breaker, so the
breaker can prevent an accident if a short
circuit occurs. Connections should never
be made to the primary side of a breaker,
because unrestricted current flow could
cause a serious accident if a short circuit
occurs.

• When the Clamp-on probe is opened, do
not allow the metal part of the clamp to
touch any exposed metal, or to short
between two lines, and do not use over
bare conductors.

• Never apply v olt age to the Clamp-on probe
when a current measurement function is
selected. Doing so may damage the prod­uct and result in personal injury.

2.3 Current Measurement

22

• To prevent damage to the product and sensor,
never connect or disconnect a probe while the
power is on.

• Check the position of the range switch of the
Clamp-on probe before taking measurements.

• Make sure the range setting of the product is the

same as that of the Clamp-on probe before start­ing measurement. If the ranges differ, an accu­rate current measurement will not be displayed.

• Attach the clamp around only one conductor.

Single-phase (2-wire) or three-phase (3-wire)
cables clamped together will not produce any
reading.

OK

• For details on each Clamp-on probe, see the

respective Instruction Manual.

23

1.

l

-

t

s

-

t

-

-

s

When the measurement
range is set to 100A

9010

3255-50

2.3 Current Measurement

Move the function selector to
the CLAMP position.

( lights up)

2. Set the measurement range

of the Clamp-on probe
(option).

If you are not sure of the leve
of the current to be mea
sured, select a large range.

3. Press the RANGE button and

select the same range as tha
of the Clamp-on probe.

LOAD

SOURCE

Conductor

Position the clamp with
the current direction in­dicator pointing toward
the load side.

The Auto Range function i
not available for current mea
surement.

Make sure the rang e setting of
the product is the same as that
of the Clamp-on probe before
starting measurement.

4. Clamp the measuremen

object, and read the indicated
value.
Change the range in accor

dance with the actual mea
surement. If the range of the
Clamp-on probe is changed
during measurement, change
the range of the product a
well.

Appearance of O.F...............

The measured value exceeds maximum
display counts
10, 100, 1000-A range: display up to 999
20, 200-A range: display up to 1999
50, 500-A range: display up to 499

2.4 Resistance Measurement

24

o

e
d

2.4 Resistance Measurement

• Never apply voltage to the test leads
when the Resistance function is
selected. Doing so may damage the
product and result in personal injury.

• To avoid electrical accidents, remove
power from the circuit before measuring.

1. M ove the function selector t

the Ω position.
( lights up)

Black

Selecting the manual range...
Reselecting the auto range

Holding the measured
value

(page 29) ................

Red

....

2. Connec t the test leads to th

measurement object, an
read the indicated value.

Press RANGE("AUTO" is turned off)
Press RANGE (for at least 1 second)

("AUTO" lights up)
Press SHIFT(for at least 1 second)→

Measurement→Intermitt ent sound→
Move the test leads away from the mea­surement objec t.

25

2.5 Continuity Check

o

-

T

e

-

2.5 Continuity Check

• Never apply voltage to the test leads
when the Continuity check function is
selected. Doing so may damage the
product and r esult in personal injury.

• To avoid electrical accidents, remove
power from the circuit before measuring.

1. Move the fu nction selector t

the Ω position.

2. Select Continuity check func

Black

Red

tion
button ( lights up).

()

using the SHIF

3. Connect t he test leads to th

measurement object.

When the continuity (thresh­old: 45±35 Ω or less) is estab
lished, the beeping sounds
and the resistance is dis­played (fixed to the 420-Ω
range).

2.6 Diode Check

26

o

n

t-

e

d
a

a

2.6 Diode Check

• Never apply voltage to the test leads
when the Diode Check function is
selected. Doing so may damage the
product and result in personal injury.

• To avoid electrical accidents, remove
power from the circuit before measuring.

1. Move the function selector t

the Ω position.

Cathode Anode

Forward
direction

Black

If displays for both directions
are the same, the following
may have occurred:

• The diode has malfunc­tioned.

Red

2. Select Diode check functio

()
ton twice ( lights up).

3. Connect the test leads to th

measurement object.
The display shows forwar

voltage (0.15 V to 2.0 V) for
normal diode.

When the diode is connected
in the forward direction (with
beeping sound):

When the diode is invertedly
connected or broken:

pressing the SHIFT

bu

• The forward voltage of the
diode is out of the mea­surement range.

27

3.1 Auto Range Function and Manual Range

Additional
Functions

Chapter 3

3.1 Auto Range Function and Manual
Range Function

Functions

Auto range function_______________________

Auto range function: V/
Manual range function: V/ / CLAMP

The Autoranging function automatically selects the
optimum measurement range.
Turning on the power also switches Autoranging

(AUTO lights up).

on
The range automatically switches up when the dis-

play shows 4200 counts or more, and down when
the display shows less than 400 counts. (A beep
sound is generated when the 3255-50 is switched
to a different range, and decimal point is dis­played.)

3.1 Auto Range Function a nd Manual Range

28

Manual range function ____________________

Press the RANGE button to active the manual
range function (AUTO is turned off).
Only Manual Range is available for current mea­surement (CLAMP).

Range selection:

V/ Ω Each pressing of the RANGE button selects the

next larger range. After the largest range, pressing
the select button again returns you to the smallest
range.

CLAMP Each pressing of the RANGE button selects the

next smaller range. After the smallest range,
pressing the select button again returns you to the
largest range.

Switching from Manual Range to Auto
Range:

Press and hold down the RANGE button (for about
1 second). (AUTO lights up)

29

3.2 HOLD AUTO Function

e

-

-

is

y

-

)

3.2 HOLD AUTO Function

Functions
Description

(example: )

HOLD

(blinks)

HOLD

(lights up)

Beeping
sound

V/ mV/

Simply moving the test leads away from the mea­surement object holds the measured value.
This function is useful when it is difficult to read
the displayed value in the current locat ion or both
hands are being used to conduct the measure­ment.

1. Move the function selector to th

desired position.

2. Pres s the SHIFT button.

(HOLD blinks)

In the measurement of resistance,
O.F is displayed.

3. Connect the test leads to the mea

surement object.
After the measured value is stabi-

lized, an intermittent sound is gener
ated.

(HOLD lights up)

4. When the intermittent sound

heard, move the test leads awa
from the measurement object.

HOLD

(blinks)

The measured value
is held.

The measured value immediately be
fore the test leads are removed is
held.

(HOLD blinks)

Blind zone V/ mV: less than 400 counts

Ω: 4200 counts or more

Canceling the HOLD AUTO mode:

Press SHIFT again. (HOLD is turned off

3.3 Overflow Warning Function

30

3.3 Overflow Warning Function

Functions
Description

O.F is displayed and an intermittent sound is ge nerated also in
the cases described below.

Voltage
measurement

Current
measurement

V/ mV/ CLAMP

When the measured value exceeds the maxi­mum indication (4199 counts), O.F is displayed
and an intermittent sound is generated.

Range

1000 V 1099 1100 or more
10/ 100/ 1000 A 999 1000 or more

20/ 200 A 1999 2000 or more
50/ 500 A 499 500 or more

Maximum
display value

O.F display

Example: When the measur ed value exceeds 1099 V in the

AC voltage measurement ( V)

The Overflow Warning function is disabled while
the HOLD AUTO function is on.

31

3.4 Auto Power Save Function

3.4 Auto Power Save Function

Functions
Description

All functions
Approximately 10 minutes after completing final

operation, the measurement product automati­cally enters Power Sa ve mode. When the mea­surement product is turned on, it automatically
enters Auto Power Save mode (APS lights up).

• In Power Save mode, the LCD is blank but power
is supplied to the measurement product.

• To avoid battery depletion, turn the function
selector OFF after use (the Auto Power Save
feature consumes a small amount of current).

Recovery from Power Save mode:

Turn of f the function selector.
After the measurement product exits Power Save

mode, all conditions are reset . If the measurement
product is to be used for an extended period, Auto
Power Save mode should be canceled in advance.

Canceling the Auto Power Save function:

Turn on the measurement product while pressing
the SHIFT button. (Hold down the button until the
beeping sound is generated.)

The Auto Power Save function is disabled until the
measurement product is turned off (APS is turned
off).

3.4 Auto Power Save Function

32

33

4.1 General Specifications

Specifications Chapter 4

4.1 General Specifications

General

Measurement
method

AC measurement
system

Function DC voltage ( V), AC voltage( V),

Additional function Auto Range function (AUTO)

Circuit protection Circuit current-limiting resistor

Dual integration

Average rectifying measurement

AC current ( ) (using with the optional
clamp-on probe), Resistance (
Continuity check( ), Diode check( )

(judgment only)

Manual Range function
Hold Auto function (HOLD)
Auto Power Save function (APS)
Battery-Life Warning function
Overflow Warning function (OF)

Protective fuse [Model DMM-44/100, fast­acting, Rating 0.44 A/1000 V (AC/DC),
breaking capacity 10 kA (made by Cooper
Bussmann*) *:
Bussmann Division, USA]

Cooper Industries Inc.,

Ω),

Display type TN type LCD, 1/4 duty, dynamic drive
Display elements 3(1/2) dgt. Max. 4199 counts

Units and symbols

1000V AC/DC range 1099 counts
Polarity indicator: "–" sign (automatic)
Overflow indicator: "OF" or "–OF"
Clamp range indicator (10 to 1000)

(AC), (DC), , AUTO, HOLD, ,

, APS, (CLAMP), M, k, m, V, Ω, A

4.1 General Specifications

34

General

Range switching Auto/Manual Range
Sampling rate 2.5 S/s
Input terminals +(V, Ω, continuity, diode) terminal

COM terminal
Functions OFF/ V/ mV/ CLAMP/ Ω
Buttons SHIFT, RANGE
Power supply Two manganese (R03) batteries or

two alkaline (LR03) batteries
Battery-life

warning
Dimensions Approx.70W × 145H × 31D mm

Mass Approx. 210 g (7.4 oz) (including batteries)
Operating

environment
Operating temper-

ature and humidity
Storage tempera-

ture and humidity

Accessories Instruction Manual

indicates low battery

(2.3 V±0.15 V or less)

(2.76"W × 5.71"H × 1.22"D)

without protrusions

(

Indoors, altitude up to 2000 m (6562-ft.)

0 to 40°C (32 to 104°F), at 80%RH or less

(non-condensating)

-20 to 40°C (-4 to 104°F), at 80%RH or

less (non-condensating)

40 to 60°C (104 to 140°F), at 70%RH or

less (non-condensating)

T wo R03 manganese batteries

9207-10 TEST LEAD

)

(for monitor )

Options 9010 CLAMP ON PROBE

9371 CARRYING CASE

9018 CLAMP ON PROBE

35

4.1 General Specifications

Applicable Standards

Safety EN61010-1:2001

EN61010-031:2002
Pollution Degree 2
Measurement Category CAT III 600 V,
CAT II 1000 V (Anticipated T ransient Over­voltage: 6000 V)

EMC EN61326:1997+A1:1998+A2:2001

+A3:2003

Dustproof and

EN60529:1991 IP54

waterproof

Electrical Chara ct eri st ics

Measurement
accuracy

Accuracy guaran­tee for tempera­ture and humidity

Regulated power
supply range

Temperature
characteristic

Noise suppression
NMRR

Noise suppression
CMRR

See accuracy table (page 37)

23°C±5°C (73°F± 9°F), 80%RH or less
(non-condensating)

3.4 V or lower (until the mark lights up)
(Measurement accuracy) × 0.1/°C

(except 23°C±5°C)
DCV: 40dB or better (50/60 Hz)

ACV: 40dB or better (DC)
DCV:100dB or better (50/60 Hz)

ACV: 60dB or better (50/60 Hz)

(1 kΩ Unbalance)
Dielectric strength
Maximum input

voltage
Maximum rated

voltage between
input terminals and
ground

Input terminals to case: 5.55 kVrms sin

(50/60 Hz for one minute)

7

1000 VDC/ 1000 Vrms(sin) or 10

V•Hz

1000 VDC/ 1000 Vrms(sin) (CAT II) or

7

10

V•Hz

600 VDC/ 600 Vrms(sin) (CAT III) or

7

10

V•Hz

4.1 General Specifications

36

Electrical Characteristics

Rated power
supply voltage

Maximum rated
power

Rated power 4 mVA (Typ) (supply voltage 3.0 VDC,

Power during auto
power saving

Continuous
operating time

3.0 VDC

12 mVA (Max) (supply voltage 3.0 VDC)

in DCV mode)

0.1 mVA (Max)
(supply voltage 3.0 VDC, during Auto
Power Saving)

Approx. 200 hours (in DCV mode, with
R03 manganese batteries)
Approx. 500 hours (in DCV mode, with
LR03 alkaline batteries)

37

4.2 Accuracy

4.2 Accuracy

Accuracy Table

(Accuracy guaranteed for one year at 23°C±5°C (73°F±9°F),
80%RH or less.)

(rdg.: displayed value, dgt.: resolution)

Voltage Measurement

mV
V

Range

[V]

420.0 m

4.200

42.00

420.0
1000

Accuracy

±(rdg.)±(dgt.)

±1.0%±4
±1.0%±4
±0.5%±4
±0.7%±4
±0.7%±4

Approx.10 MΩ
Approx.11 MΩ
Approx.10 MΩ
Approx.10 MΩ
Approx.10 MΩ

(50
Approx.10 MΩ
Approx.11 MΩ
Approx.10 MΩ
Approx.10 MΩ
Approx.10 MΩ

mV
V

420.0 m

4.200

42.00

420.0
1000

±2.0%±4
±2.0%±4
±1.2%±4
±1.5%±4
±1.5%±4

Overload protection (for one minute):

7

1000 VDC,1000 Vrms(sin) or 10

V•Hz

Input Impedance

(Frequency range)

to 500 Hz)

4.2 Accuracy

38

(rdg.: displayed value, dgt.: resolution)

Current Measurement

(3255-50 only. For accuracy of the combination of the Clamp-on
probe and the 3255-50, add the measurem ent accuracy of the
clamp-on probe)

CLAMP

(ACA)

Range

[A]

10.00

20.00

50.0

100.0

200.0
500
1000

Accuracy

±(rdg.)±(dgt.)

±2.0%±4
±2.0%±4
±2.0%±4
±2.0%±4
±2.0%±4
±2.0%±4
±2.0%±4

Input Impedance

(Frequency range)

Approx.10 MΩ
(50 to 500 Hz)

Overload protection (for one minute):

7

1000 VDC,1000 Vrms(sin) or 10

V•Hz

Resistance Measurement/ Continuity Check/
Diode Check

(Resis­tance)

Range

[Ω]

420.0

4.200 k

42.00 k

420.0 k

4.200 M

42.00 M

Accuracy

±(rdg.)±(dgt.)

±1.0%±8
±0.7%±4
±1.0%±4
±1.0%±4
±2.0%±4
±5.0%±4

Open terminal

voltage

3.4 V or less
Approx.0.7 V
Approx.0.5 V
Approx.0.5 V
Approx.0.5 V
Approx.0.5 V

Notes

Measurement
current: 850 μA
max.
Varies accord­ing to resistance
levels to be
measured.

(Continu­ity)

420.0 ±1.0%±8 3.4 V or less
Judgment only

(Diode)

(0.15V to 2.00V) 3.4 V or less

Overload protection (for one minute):
1000 VDC,1000 Vrms(sin) or 10

7

V•Hz

Threshold:
45 Ω±35 Ω

Measurement
current:
850 μA max.

39

5.1 Replacing the Batteries and Fuses

Maintenace and
Service

Chapter 5

5.1 Replacing the Batteries and Fuses

• To avoid electric shock when replacing the
batteries and fuses, first disconnect the
test leads from the object to be measured.

• Before using the product after replacing
the batteries or fuses, replace the cover
and screw.

Replacing the Batteries

• Do not mix old and new batteries, or differ­ent types of batteries. Also, be careful to
observe battery polarity during installation.
Otherwise, poor performance or damage
from battery leakage could result.

• To avoid t he poss ibility of explo si on, do not
short circ ui t, d isas sem bl e or i ncine rate bat­teries.

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

• The “ ” indicator appears when battery voltage

becomes low. Replace the batteries as soon as
possible.

• Use R03 manganese dry cells or LR03 alkaline

dry cells.

5.1 Replacing the Batteries and Fuses

40

Replacing the Fuses

Replace the fuse only with one of the speci­fied characteristics and voltage and current
ratings. Using a non-specified fuse or short­ing the fuse holder may cause a life-threat­ening hazard .
Fuse type:
Model DMM-44/100, Fast-acting, Rating:

0.44 A/1000 V (AC/DC), Breaking capacity:
10 kA (made by Cooper Bussmann)

Be careful not to damage the circuit board or cas e
when changing fuses. If removing the fuse by
hand, be careful not to hurt your nails or fingers.

When measurement cannot be performed, the
fuse may have blown due to excess current. When
the fuse has blown, the beeping sound will not be
generated during a continuity check.

Fuse Protection Circuitry

A 5 Ω protective resistor and 0.44 A safety fuse
(1000 V AC/DC, 10 kA cut-off capacity) are
installed in series with the positive terminal of the
instrument to prevent short-circuit accidents during
voltage measurement of power line circuits. If a
short occurs in the instrument circuitry, current flow
is limited by the protective resistance until the
safety fuse opens. The protect ive resistance limits
the short-circuit current, minimizing arcing at the
tip of the test probe and providing safer operation.

41

s

t
e
n

r

-

e

r

­)
r

e

t

d
g

r

Front case

Front case

Fuse

5.1 Replacing the Batteries and Fuses

Necessary tool: Phillips screwdrive

1. Disconnect the test lead

from the measuremen

Rear case

circuit, and make sur
the function selector is i
the OFF position.

2. Turn the 3255-50 ove

Rear case

Batteries

and use a Phillips screw
driver to remove the on
retaining screw.

3. Lift and remove the rea

case.

4. Replace the two manga

nese batteries (R03
mounted to the rea
case, or the fus
mounted to the fron
case.

5. Mount the rear case an

tighten the retainin
screw.

Fuse type
Model:DMM-44/100, fast-acting
Rating:0.44 A/1000 V(AC/DC)
Breaking capacity:10 kA
(made by Cooper Bussmann*)
*Cooper Industries Inc., Bussmann Division, USA

5.2 Cleaning and Storage

42

5.2 Cleaning and Storage

Cleaning________________________________

• To clean the product, wipe it gently with a soft
cloth moistened with water or mild detergent.
Never use solvents such as benzene, alcohol,
acetone, ether, ketones, thinners or gasoline, as
they can deform and discolor the case.

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

Storage_________________________________

To avoid corrosion from battery leakage, remove
the batteries from the product if it is to be stored for
a long time.

43

5.3 Service

• Adjustments and repairs should be made only by
technically qualified personnel.

• If the product seems to be malfunctioning, con­firm that the batteries are not discharged, and
that the test leads, clamp-on probes, and fuse
are not open circuited before contacting your
dealer or Hioki representative.

• When sending the product for r epair, remove the
batteries and pack carefully to prevent damage
in transit. Include cushioning material so the
instrument cannot move w ithin the package. Be
sure to include details of the problem. Hioki can­not be responsible for damage that occurs during
shipment.

5.3 Service

5.3 Service

44

HIOKI 3255-50 DIGITAL HiTESTER

Instruction Manual

Publication date: September 2006 Revised edition 1
Edited and p ublished by HIOKI E .E. CORPO RATION

Technical Support Section
All inquiries to International Sales and Marketing De-

partment
81 Koizumi, Ueda, Nagano, 386-1192, Japan
TEL: [phone] / FAX: [phone]
E-mail: [e-mail]
URL http://www.hioki.co.jp/

Printed in Japan 3255AD981-01

• All reasonable care has been taken in the production
of this manual, but if you find any points which are
unclear or in error, please contact your supplier or the
International Sales and Marketing Department at
HIOKI headqu arte rs.

• In the interests of product development, the contents
of this manual are subject to revision without prior
notice.

• Unauthorized reproduction or copying of this manual
is prohibited.

HEAD OFFICE

81 Koizumi, Ueda, Nagano 386-1192, Japan
TEL [phone] / FAX [phone]
E-mail: [e-mail]
URL http://www.hioki.co.jp/

HIOKI USA CORPORATION

6 Corporate Drive, Cranbury, NJ 08512, USA
TEL [phone] / FAX [phone]

3255D981-01 06-09H

Printed on recycled paper