Instruction manual

Compact Insulation resistance tester with 3-range

KEW MEG series

MODEL3321A, 3322A, 3323A
KYORITSU ELECTRICAL INSTRUMENTS
WORKS,LTD.

Contents
1．Safety warnings ……………………………………………………１
2．Features ……………………………………………………………３
3．Specification ………………………………………………………４
4．Instrument layout …………………………………………………８5．Preparation for measurement
5－1 Mechanical zero adjustment ………………………………９5－2 Test lead connection ………………………………………９5－3 Battery voltage check ………………………………………10
5－4 Power-on-indication LED …………………………………10
6．Measurement
6－1 AC voltage measurement …………………………………10(Mains disconnection check)
6－2 Insulation resistance measurement ………………………12
6－3 Continuous measurement …………………………………14
6－4 Output voltage characteristics ……………………………14
6－5 Using guard terminal (only for MODEL3321A) …………16
6－6 Backlight function …………………………………………16
7．Battery replacement ………………………………………………17
8．Notes on Housing case and accessories
8－1 Case lid ……………………………………………………18
8－2 Neck strap and Cord case …………………………………18
8－3 Test prods and replacement ………………………………19
8－4 Adaptors for the Earth cord and replacement …………20
8－5 Cleaning Meter cover ……………………………………21

１．Safety warnings◯ This instrument has been designed, manufactured and tested
according to IEC 61010-1: Safety requirements for Electronic
Measuring apparatus, and delivered in the best condition after
passed the inspection. This instruction manual contains
warnings and safety rules which must be observed by the user
to ensure safe operation of the instrument and retain it in safe
condition. Therefore, read through these operating instructions
before using the instrument.

# WARNING◦Read through and understand the instructions contained in thismanual before using the instrument.
◦Keep the manual at hand to enable quick reference whenevernecessary.
◦The instrument is to be used only in its intended applications.
◦Understand and follow all the safety instructions contained in
the manual.
It is essential that the above instructions are adhered to. Failure
to follow the above instructions may cause injury, instrument
damage and/or damage to equipment under test.
◯ The symbol # indicated on the instrument, means that the user
must refer to the related parts in the manual for safe operationof the instrument. It is essential to read the instructions
wherever the # symbol appears in the manual.

# DANGER ：is reserved for conditions and actions that arelikely to cause serious or fatal injury.

# WARNING：is reserved for conditions and actions that cancause serious or fatal injury.

# CAUTION ：is reserved for conditions and actions that cancause injury or instrument damage.

̶1̶# DANGER◦Never make measurement on a circuit in which the electricalpotential exceeds AC/DC600V(Measurement CAT. III 600V).
◦Do not attempt to make measurement in the presence of flammablegasses. Otherwise, the use of the instrument may cause sparking,which can lead to an explosion.
◦Never attempt to use the instrument if it's surface or your hand are wet.
◦Be careful not to short-circuit the power line with the metal part of thetest leads when measuring a voltage. It may cause personal injury.
◦Do not exceed the maximum allowable input of any measuring range.
◦Never open the Battery cover during a measurement.

# WARNING◦Never attempt to make any measurement if any abnormal conditions,such as a broken case or exposed metal parts are present on theInstrument and test leads.

◦Never press the Test button while connecting the test leads.
◦Never rotate the Range switch with the test leads connected to theequipment under test.

◦Do not install substitute parts or make any modification to the

instrument. Return the instrument to your local KYORITSU
distributor for repair or re-calibration in case of suspected faulty
operation.
◦Never touch the circuit under test during/immediately after the
insulation resistance measurement. The test voltage may cause
electrical shock.
◦Do not replace batteries if the instrument is wet.
◦Ensure that the test leads are firmly inserted into the terminal.
◦Set the Range switch to OFF position when opening the Battery
cover for battery replacement.

# CAUTION◦Always set the Range switch to the appropriate position before
making measurement.

◦Set the Range switch to "OFF" position after use and remove the test

leads. The instrument consume small current at any range otherthan OFF, and it shortens the battery life. Remove the batteries if the
instrument is to be stored and will not be in use for a long period.
◦Do not expose the instrument to direct sunlight, high temperatures,
humidity or dew.
◦Use a damp cloth with neutral detergent for cleaning the instrument.
Do not use abrasives or solvents.
◦Do not store the instrument if it is wet. Store it after it dries.

̶2̶

２．Features
MODEL3321A/ 3322A/ 3323A are three-range insulation resistancetesters for testing low-voltage installation below 600V.
◦Designed to following safety standards:
IEC 61010-1, IEC 61010-031, IEC 61557◦Small and light weight.
◦Auto-discharge function
When insulation resistance like a capacitive load is measured,
electric charges stored in capacitive circuits are automaticallydischarged after measuring. Discharge can be checked with themeter.
◦Color-coded scales for easy and correct reading◦Power-on indicator on insulation resistance and battery check
ranges.
◦Backlight function to facilitate working at dimly illuminatedlocation or at nighttime work.
◦AC voltage measurement function
Measures AC voltage on all ranges without pressing the Test
button◦Test leads with remote control switch(voltage won't be outputted when the test lead is not connected.)◦Robust housing case
◦Neck strap for both hand's operation◦User-changeable test prod

̶3̶

３．Specification◦Applicable standards
IEC 61557

IEC 61010-1 Measurement CAT.III 600V Pollution degree2
Protection class II

Location for use: altitude 2000m or lessIEC 61010-031
IEC 60529
IP40◦Measuring range and accuracy<Insulation resistance range>
MODEL3321A
Nominal voltage
250V
500V
1000V
Max. effective scale value
50MΩ
100MΩ
2000MΩ
Mid-scale value
1MΩ
2MΩ
50MΩ
0.05～20MΩ 0.1～5MΩ
2～1000MΩ
Accuracy in primaryeffective measuring ranges
within ±5% of indicated value
Accuracy in primary
Measuring ranges other than above, 0 and ∞.
effective measuring ranges
within ±10% of indicated value
Accuracy at 0 and ∞within ±0.7% of scale length
Accuracy at no-load
0%～+20% of nominal voltage
voltageNominal current
1mA 0%～+20%
Short-circuit current
within 1.5mA* Heavy-line circular arc on the scale indicates the primary effective
measuring ranges. (guaranteed accuracy range)
MODEL3322A
Nominal voltage
125V
250V
500V
Max. effective scale value
20MΩ
50MΩ
100MΩ
Mid-scale value
0.5MΩ
1MΩ
2MΩ
0.02～10MΩ 0.05～20MΩ 0.1～50MΩ
Accuracy in primaryeffective measuring ranges
within ±5% of indicated value
Accuracy in primary
Measuring ranges other than above, 0 and ∞.
within ±10% of indicated value
effective measuring ranges
Accuracy at 0 and ∞within ±0.7% of scale length
Accuracy at no-load
0%～+20% of nominal voltage
voltage
1mA 0%～+20%
Nominal current
Short-circuit current
within 1.5mA* Heavy-line circular arc on the scale indicates the primary effective
measuring ranges. (guaranteed accuracy range)
̶4̶

MODEL3323A
Nominal voltage
Max. effective scale value
Mid-scale value
Accuracy in primaryeffective measuring ranges
Accuracy in primaryeffective measuring ranges
Accuracy at 0 and ∞Accuracy at no-load
voltageNominal current
Short-circuit current

25V
50V
100V
10MΩ
10MΩ
20MΩ
0.2MΩ
0.2MΩ
0.5MΩ
0.01～5MΩ 0.01～5MΩ 0.02～10MΩ
within ±5% of indicated value
Measuring ranges other than above, 0 and ∞.
within ±10% of indicated value
within ±0.7% of scale length
0%～+20% of nominal voltage
1mA 0%～+20%
within 1.5mA* Heavy-line circular arc on the scale indicates the primary effective
measuring ranges. (guaranteed accuracy range)<Operating error>
Operating error (B) is an error obtained under the nominal
operating conditions, and calculated with the intrinsic error (A),which is an error of the instrument used, and the error (En) due tovariations. According to IEC61557, the maximum operating error
should be within +/-30%.
Ｂ ＝︱Ａ︱＋ 1.15 × √（ Ｅ12 ＋ Ｅ22 ＋ Ｅ32 ）Ａ ： Intrinsic error (%)
Ｂ ： Operating error (%)
Ｅ1： Variation due to changing the temperature (%)
Ｅ2： Variation due to changing the Battery voltage (%)
Ｅ3： Variation due to changing the position (%)
Nominal operating conditions
Ambient temperature: 0～40℃
Relative humidity: 90% or less
External magnetic field : 400A/m or lessPosition: Horizontal～±90°
Battery voltage: within "BATTERY. GOOD" range

̶5̶

<AC voltage range>
Measured voltage

0 ～ 600V
within ± 3% of max scale value (ACV range)
within ± 5% of max scale value (Others)

Accuracy<Number of measurement>
Possible number of measurement within the "BATTERY.GOOD"
range.(Measure 5 sec., and take pause for 25 sec.)
Range

Resisterfor test

Possible numberof measurement

25V/10MΩ

0.025MΩat least 4000 times

50V/10MΩ

0.05MΩ

at least 3500 times

100V/20MΩ

0.1MΩ

at least 3000 times

125V/20MΩ

0.125MΩat least 2500 times

250V/50MΩ

0.25MΩ

at least 2000 times

500V/100MΩ

0.5MΩ

at least 1000 times

1000V/2000MΩ

1MΩ

at least 300 times

Temperature & humidity
range
Storage temperature &humidity range
Response time

Insulation resistanceWithstand voltage: 0℃～40℃ (RH: 85% or less)(no condensation): -20℃～＋60℃ (RH: 75% or less)(no condensation): Meter reading comes within accuracy
within 3 sec. after a resistancecorresponding to the mid-scale valueand 0Ω is suddenly applied acrossthe measuring terminals.
(It may take time when measuring acapacitive load.): at least 100MΩ/ DC1000V between
the electrical circuit and the enclosure: AC5, 550V(50/60Hz) for 1 min. between
the electrical circuit and the enclosure̶6̶◦Overload protection
The instrument operates properly after each of the voltage shownin the table below is applied for 10 sec.
MODEL
Insulation
resistanceAC voltage

3321A
1000V range : AC 1200V
The other ranges : AC 600V
AC 1200V

Dimension
WeightPower source
Nominal power

3322A
3323A
All ranges : All ranges :AC600VAC AC360VAC
720V
720V

: approx. 105(L) x 158(W) x 70(D)mm: approx. 520g (including batteries): R6P (SUM-3), AA, x 6pcs
: 3.5VA

Accessories
MODEL7103A Test lead with remote control switch
MODEL7081 Guard cord (Only for MODEL3321A)
MODEL7161A Flat test bar
MODEL7131B Safety alligator clip
MODEL8017 Extension prod
Neck strap
Cord case
R6P (SUM-3), size AA
Instruction manual

1 set
1 pce
1 pce
1 pce
1 pce
1 pce
1 pce
6 pcs
1 pce

Optional
MODEL7115 Extension probe
MODEL8016 Pickle type prod

Pickle type prod

Extension probe
̶7̶

４．Instrument layout
Fig. 1 Instrument layout①Meter zero adjuster②Test button③Scale plate④Pointer⑤Insulation resistance scale⑥AC voltage scale⑦"BATTERY-GOOD" range⑧Power-on-indication LED⑨Guard terminal⑩Probe socket⑪Backlight switch⑫Range switch⑬Test lead with remote control switch (MODEL7103A)⑭Remote control switch⑮Line probe⑯Earth cord
⑰Standard prod (MODEL8072)⑱Probe connector⑲Flat test bar (MODEL7161A)⑳Safety alligator clip(MODEL7131B)
Extension prod (MODEL8017)
Test lead for Guard terminal (MODEL7081)※ Item⑨andare only for MODEL3321A.
̶8̶

５．Preparation for measurement
5−1 Mechanical zero adjustment
With the Range switch set to the OFF position and withoutpressing the Test button, turn the Zero adjuster with ascrewdriver so that the pointer lines up with the "∞" mark on an
insulation resistance scale. In case the instrument is used at thesloping place, ensure that the pointer lines up with the "∞" marktilting the instrument to the necessary angle.
5−2 Test lead connection
Insert the Probe connector into the Probe socket on the
instrument correctly as shown below.

Probe connector

Probe socket# DANGER
When the Test button or the Remote control switch is pressedwith the Range switch set to an insulation resistance range,take care not to touch the tip of the Test probe where a highvoltage is present in order to avoid possible shock hazard.

̶9̶

5−3 Battery voltage check(1) Set the Range switch to the BATT. CHECK position.
(2) Press the Test button or Remote control switch.
(3) If the meter pointer does not move to BATT GOOD, replace
the batteries as shown in Section 7 "Battery replacement".
Batteries have exhausted.
Replace the batteries.

Proceed to measurement.

# CAUTION
Never keep the Test button pressed or locked during battery
check to avoid battery power drain.
5−4 Power-on-indication LED
On an insulation resistance range or BATT. CHECK range,
when the Test button or Remote control switch is pressed, thepower-on-indication LED (red) lights up, indicating the
instrument is in the operation mode.

６．Measurement
6−1 AC voltage measurement (Mains disconnection check)
The AC voltage measurement function is available on any
ranges.
(1) Connect the Earth probe to the earth of the circuit under testand Line probe to the other side. If the circuit is not earthed,connect Earth probe to any appropriate conductor.
(2) Without pressing the Test button or Remote control switch,take the reading on the AC voltage scale.
̶ 10 ̶

CAUTION
Never press
remote switcth

CAUTION
Never press
test button

AC voltage measurement (Mains disconnection check)
The AC voltage measurement function is available on any ranges.

# DANGER◦Never make measurement on a circuit in which the electricalpotential exceeds AC/DC600V in order to avoid possible
shock hazard.
(Refer to Section 3. "Specification, AC voltage measurement.)◦When testing installation that has a large current capacity,such as a power line, be sure to make measurement on thesecondary side of a circuit breaker in order to avoid personal
injury.
◦Do not press the Test button or Remote control switch during
voltage measurement.
◦Never short live conductors with the tip of a probe to avoid
personal injury.
◦Do not make measurement with the Battery cover removed.
<Simplified measurement of DC voltage>
This instrument also provides simplified measurement of DC
voltage. Multiplying 0.9 by the indicated value at AC voltage scale
provides the DC voltage value. However, the polarity isn't
indicated.
DC voltage (V) = Indicated value at AC voltage scale x 0.9 (V)̶ 11 ̶

6−2 Insulation resistance measurement
Before performing any insulation test, check the maximum
voltage that may be applied to the circuit under test.
Note:◦Some circuits have an unstable insulation resistance, whichcauses the reading to vary during measurement.
◦The instrument may generate a high pitch tone during
measurement. This is not a failure.
◦If the circuit under test has a large capacitive load, it may takesome time before the final reading can be obtained.
◦On insulation resistance range, DC voltage is supplied throughEarth and Line probes, with Earth probe having positive polarity.
Earth probe should be connected to the earth conductor in thecircuit under test. Such connection is known to be more suitablefor insulation tests since an insulation resistance value measured
with the positive side connected to earth is typically less than thattaken through the reversed connection.

# DANGER◦When the Test button or Remote control switch is pressedwith the Range switch set to an insulation resistance range
position, take care not to touch the tip of the test probe or thecircuit under test where a high voltage is present in order toavoid possible shock hazard.
◦Do not make measurement with the Battery cover removed.
# CAUTION
Ensure that the circuit under test is de-energized prior to any
insulation testing.
(1) Check the maximum voltage that may be applied to the circuitunder test. Set the Range switch to a desired insulation
resistance range.

̶ 12 ̶

(2) Connect Earth probe to the earth terminal of the circuit under
test. If the circuit is not earthed, connect Earth probe to any
appropriate conductor.
(3) Connect Line probe to the circuit under test and press the Test
button or Remote control switch.
(4) Take the reading on the scale for the selected insulation
resistance range.
Connect side Earth terminal
source side
Circuit breaker
Remote control switch

CAUTION
Make sure to turnLoad side oﬀ the circuit
breaker.

Press the test button or remote control switch.

Test button

Select range(5) Release the Test button or Remote control switch and leave theprobes connected to the circuit under test to discharge charges
stored in the capacitance of the circuit.

# DANGER◦Do not touch the circuit under test immediately after testing.
Charges stored in the capacitance of the circuit may cause
electrical shock.
◦Leave the probes connected to the circuit under test until the
pointer returns to the left end of the scale. Never touch thecircuit before the discharging completes.
̶ 13 ̶

<Auto discharge function>
This function allows electric charges stored in the capacitance ofthe circuit under test to be automatically discharged after
testing. Discharge can be monitored by the AC voltage reading.
(6) Set the Range switch to the OFF
position, and disconnect the probes
from the instrument.
6−3 Continuous measurement
For continuous measurement, a lock-down feature isincorporated on the Test button. Pressing and turning clockwise
locks the button in the operating position, the button is releasedby turning it counterclockwise.

# DANGER
While the Test button is locked down, a high voltage is present
at the tip of a probe. Attention should be paid to avoid possible
shock hazard.
6−4 Output voltage characteristics
This instrument conforms to IEC61557. This standard definesthat the nominal current shall be at least 1mA, and the lower
limit of the insulation resistance maintaining the nominal voltage
at the measurement terminal. (See the graph below.)This value is calculated by dividing the nominal voltage by
nominal current. i.e., in case that the nominal voltage is 500V,
the lower limit of the insulation resistance is found as follows.
Divide 500V by 1mA equals 0.5MΩ
That is, insulation resistance of 0.5MΩ or more is required toprovide the nominal voltage to the instrument.
Nominal voltage

25V

Lower limit of insulation 0.025
resistance to supplyMΩ
nominal current (1mA)

50V
0.05
MΩ

100V 125V 250V 500V 1000V
0.1 0.125 0.25
0.5
1MΩ MΩ MΩ MΩ MΩ

̶ 14 ̶

Output Voltage[V]

range

range
range

Insulation Resistance[MΩ]

Output Voltage[V]

range

range
range

Insulation Resistance[MΩ]

Output Voltage[V]

range

range
range

Insulation Resistance[MΩ]̶ 15 ̶

6−5 Using Guard Terminal (only for MODEL3321A)
Shown below is an example of the insulation resistancemeasurement of an electric wire. If Line probe is simply
connected to the wire conductor and Earth probe to the woven
metal shield as shown, a measurement error will be introduced
as this results in the measurement of the combined resistanceof insulation resistance and the surface leakage resistance at
the cut end of the electric wire. In order to remove this surface
leakage current, wind a guard wire around the cut end of the
conductor and connect it to the guard terminal of the instrument
using Guard Connection lead. Then, the surface leakage
current will bypass the meter of the instrument.
Core Conductor
Insulation

Meter
Voltage
Generator

Leakage Current

Insulalion Resistance Tester

Guard Wire
SheathedCable

6−6 Backlight function
To facilitate working in dimly lit situations, a backlight function isprovided which illuminates the scale plate. Press the backlightswitch to operate this function. The backlight will light up forabout 60 sec., and then turned off automatically.

̶ 16 ̶

7．Battery replacement# DANGER

Never open the Battery cover during a measurement.

# WARNING

To avoid possible electric shock, remove test leads before
opening the Battery cover. After replacing batteries, be sureto tighten up the screws for Battery cover.

# CAUTION

Do not mix new and old batteries.
Install batteries in correct polarity as marked inside theBattery compartment.

(1) Set the Range switch to "OFF" position, and remove the test
leads from the instrument.
(2) Loosen the Battery-cover-fixing screws, and remove the Battery
cover. Always replace all 6 batteries with new one at the sametime.
(3) After replacing batteries, be sure to tighten up the screws forBattery cover.
Battery-compartment-cover-ﬁxing Screws

Install batteries in correct
polarity as marked inside
the battery compartment.

̶ 17 ̶

8．Notes on Housing case and accessories
8−1 Case lid
Case lid can be fit under the Housing case while making
measurement.
(1) Unhook and open the Case lid.
(2) Turn it 180 degrees.
(3) Put the Case lid under the Housing case.
(4) Hook it on to the Housing case.

8−2 Neck strap and Cord caseThis instrument is equipped with a strap to suspend from theneck to allow both hands to be used freely for easy and safe
operation.

̶ 18 ̶

8−3 Test prods and replacement
1. Types of Test prods
MODEL8072: Standard Test prod
Used for ordinary measurement.
(Attached to the Line probe at the time ofpurchase.)
MODEL8017: Extension probe
Used in difficult-to-reach situations.
MODEL8016: Pickle prod (Optional)
Used to hook the probe on a conductor.
2. How to replace Test prod
To remove the Test prod, turn the cap of LINE probe
counterclockwise. Insert the threaded end of another prod
into the hexagonal hole on the probe cap as shown. Then,turn the probe cap clockwise to secure it on the body of theprobe.

Male Screw
FemaleScrew
Hexagonal Hole

Extension Prod

Prod
Pickel Prod̶ 19 ̶

8−4 Adaptors for the Earth cord and replacement
1. Adaptors
MODEL7131B: Safety alligator clip
Connected to the Earth terminal of the Earthterminal board.
MODEL7161A: Flat test bar
Connected to the earth side of the outlet.
2. How to replace Adaptors
To remove the adaptors, pull them out. Then firmly attach theadaptor as desired to the tip of the Earth cord.

Safety alligator clip

Flat test bar

̶ 20 ̶

8−5 Cleaning Meter coverThis instrument is managed by our company's quality standard
and is delivered in the best condition after passed theinspection. But in the dry time of winter static electricity
sometimes builds up on the meter cover due to thecharacteristic of plastic.
When static builds up on the meter cover and affects the meterreading, use a cloth damped with off-the-shelf anti-static agent
or detergent to wipe the meter cover surface.

# CAUTION◦When the pointer deflects by touching the surface of this
instrument or zero adjustment cannot be made, do not try to
make measurement.
◦Antistatic agent has been applied to the meter cover of the
instrument for electrification prevention, therefore, do not rub itstrongly with a dry cloth etc. even if it is dirty.
◦To avoid possible deforming or discoloring, do not use
solvents.

̶ 21 ̶DISTRIBUTOR

7-11

92-1646B