Kyoritsu Electrical Instruments Works, Ltd. KEW 3126 User manual

INSTRUCTION MANUAL
4-range High voltage insulation resistance tester
KEW 3126

Contents
1. Safety warnings ·········································································· 1
2. Feature ······················································································· 5
3. Specification ··············································································· 6
4. Instrument layout
4-1 Instrument layout ·································································· 9
4-2 LCD display ········································································ 10
5. Preparation for measurement
5-1 Checking the battery voltage ·············································· 11
5-2 Connecting test leads ························································· 11
6. Measurement
6-1 Mains disconnection check (Voltage measurement) ·········· 12
6-2 Insulation resistance measurement ···································· 13
6-3 Continuous measurement ·················································· 16
6-4 DAR/PI measurement function ··········································· 17
6-5 Voltage characteristics of measuring terminal ···················· 21
6-6 Use of Guard terminal ························································ 21
6-7 Filter function ······································································ 22
6-8 Backlight function ······························································· 22
6-9 Auto-power-off function ······················································ 22
7. Battery replacement ································································· 23
8. Accessories
8-1 Metal part for Line Probe, and replacement ······················· 24
8-2 How to use the adaptor for recorder ·································· 25
8-3 Line probe with alligator clip ··············································· 25

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1. Safety warnings
This instrument has been designed, manufactured and tested
according to IEC 61010: 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 instructions contained in this
manual before starting to use the instrument.
● Save and keep the manual at hand to enable quick reference
whenever necessary.
● The instrument is to be used only in its intended applications.
● Understand and follow all 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 related parts in the manual for safe operation of the
instrument. It is essential to read the instructions wherever the #
symbol appears in the manual.
#DANGER is reserved for conditions and actions that are
likely to cause serious or fatal injury.
#WARNING is reserved for conditions and actions that can
cause serious or fatal injury.
#CAUTION is reserved for conditions and actions that can
cause injury or instrument damage.

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#DANGER
● Never make measurement on the circuit in which electrical
potential to ground over 600V exists.
● Do not attempt to make measurement in the presence of
flammable gasses. Otherwise, the use of the instrument may
cause sparking, which can lead to an explosion.
● Never attempt to use the instrument if its surface or your hand is
wet.
● Be careful not to short-circuit the power line with the metal
part of the test leads when measuring voltage. It may cause
personal injury.
● Do not apply inputs exceeding the maximum allowable
measuring range.
● Do not press the Test button with test leads connected to the
instrument.
● Never open the battery compartment cover while making a
measurement.
● Do not touch the circuit under test while measuring insulation
resistance or right after a measurement. You may get an electric
shock by a test voltage.
#WARNING
●
Never attempt to make any measurement if any abnormal
conditions are noted, such as broken case and exposed metal parts
or when inner jackets are seen through the nicked outer jacket.
● Do not rotate the Range switch with the test leads connected to
the equipment 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.
● Do not try to replace the batteries if the surface of the
instrument is wet.
● Firmly insert the plug into the terminal when using test leads.
● Ensure that the instrument is powered off when opening the
battery compartment cover for battery replacement.

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#CAUTION
● Always make sure to set the Range switch to the appropriate
position before making a measurement.
● Set the Range Switch to “OFF” position after use and
disconnect the test leads from the instrument. Remove the
batteries if the instrument is to be stored and will not be used for
a long period.
● Do not expose the instrument to the direct sun, high
temperature and humidity or dewfall.
● Use a cloth dipped in alcohol for cleaning the test leads and the
part around the measuring terminals.
● Do not store the instrument if it is wet.
● The Voltage warning mark is being displayed during a measure-
ment and it flashes when voltages 30V(DC/AC) or more exist on
the circuit under test.
Symbols
Danger of possible electric shock
Instrument with double or reinforced insulation
DC
AC
Earth terminal
Crossed-out wheel bin symbol (according to WEEE
Directive: 2002/96/EC) indicating that this electrical
product may not be treated as household waste, but
that it must be collected and treated separately.

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○ Measurement categories(Over-voltage categories)
To ensure safe operation of measuring instruments, IEC 61010
establishes safety standards for various electrical environments,
categorized as CAT I to CAT IV, and called measurement
categories.
Higher-numbered categories correspond to electrical environments
with greater momentary energy, so a measuring instrument
designed for CAT III environments can endure greater momentary
energy than one designed for CATII.
CATI : Secondary electrical circuits connected to an AC
electrical outlet through a transformer or similar device.
CAT II : Primary electrical circuits of equipment connected to an
AC electrical outlet by a power cord.
CAT III : Primary electrical circuits of the equipment connected
directly to the distribution panel, and feeders from the
distribution panel to outlets.
CAT IV : The circuit from the service drop to the service entrance,
and to the power meter and primary overcurrent
protection device (distribution panel).

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2. Feature
KEW3126 is a microcomputer controlled, high voltage insulation
resistance tester with 4-range for measuring insulation resistance.
● Designed to following safety standards:
IEC 61010-1 (CAT.III 600V Pollution degree 2)
IEC 61010-031 (Requirements for hand-held probes)
● With auto-discharge function
When insulation resistance like a capacitive load is measured,
electrical charges stored in capacitive circuits are automatically
discharged after measuring. Discharge can be checked on the
voltage monitor.
● Backlight function to facilitate working at dimly illuminated location
or at nighttime work.
● Bar graph to display measured result
● LIVE circuit warning symbols plus audible warning
● With Auto-power off function
To prevent the instrument being left powered on and conserve
battery power, the instrument automatically turns off approx.
10 min. after the last switch operation.
● Auto-measurement and display of DAR (Dielectric Absorption
Ratio) and PI (Polarization Index)
● Filter function to reduce the variations in readings due to external
influences
● With a short current of max 5mA, quick measurement is possible
even if the object under test has capacitive components.

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3. Specification
● Applicable standards
IEC 61010-1 Measurement CAT.III 600V Pollution degree2
IEC 61010-031 Standard for hand-held probes
MODEL7165A(CAT.III 600V)
MODEL7224A(CAT.IV 600V)
MODEL7225A(CAT.IV 600V)
*
When KEW3126 and the test lead are combined
and used together, whichever is lower category
either of them belong to is applied.
IEC 61326-2-2 EMC standard
IEC 60529 IP40
● Measuring range and accuracy
(Temperature, humidity: 23±5Cº, 45 −75%RH)
<Insulation resistance tester>
Rated voltage 500V 1000V 2500V 5000V
Measuring
Range
0.0 −99.9MΩ
100 −999MΩ
0.0 −99.9MΩ
100 −999MΩ
1.00−1.99GΩ
0.0 −99.9MΩ
100 −999MΩ
1.00−9.99GΩ
10.0−99.9GΩ
0.0 −99.9MΩ
100 −999MΩ
1.00−9.99GΩ
10.0−99.9GΩ
100−1000GΩ
Open circuit
Voltage DC 500V +30%, -0% DC 1000V +20%, -0% DC 2500V +20%, -0% DC 5000V +20%, -0%
Rated
Current
1mA or more,
1.2mA or less
(at 0.5MΩ load)
1mA or more,
1.2mA or less
(at 1MΩ load)
1mA or more,
1.2mA or less
(at 2.5MΩ load)
1mA or more,
1.2mA or less
(at 5MΩ load)
Short-circuit
current For 10 sec after a test is started : max 5mA, after that : 1.4mA
Accuracy ±5%rdg±3dgt
100GΩ or more,
±20%rdg
Voltage monitor for insulation resistance range
30 −6000V (resolution 10V): ±10%rdg±20V

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This monitor is used to check whether electrical charge stored
on the equipment under test is discharged or not. The measured
voltage value displayed on the LCD is a reference value.
Please be noted that the indicated value, when external AC
voltage is applied to the instrument, is not the correct value.
<Voltmeter> DC voltage AC voltage
Measuring range ±30 −±600V 30 −600V(50/60Hz)
Resolution 1V
Accuracy ±2%rdg±3dgt
●Display: Liquid crystal display
Insulation resistance range: Max.999 counts
(1000 counts only at 1TΩ display)
V range: Max. 630 counts
Bar graph : Max. 36 points
DAR/PI value : 9.99
Time: 60:00
●Low battery warning: Battery mark display (in 4 levels)
●Overrange indication: “OL” mark appears at insulation resistance
range and “Hi” mark at voltage range.
●Auto-ranging: Range shifts to upper range : 1000 counts
Range shifts to lower range : 80 counts
(Only at the insulation resistance range)
●Auto-power-off: Power off function operates in 10 min. after
the last switch operation.
●Used location: altitude 2000 m or less
●Temperature & humidity range (guaranteed accuracy):
23ºC±5ºC/Relative humidity 85% or less
(no condensation)
●Operating temperature & humidity range:
0ºC to 40ºC/Relative humidity 85% or less
(no condensation)
●Storage temperature & humidity range:
-20ºC to +60ºC/Relative humidity 75% or less
(no condensation)

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●Overload protection: Insulation resistance range: AC1200V/10sec.
Voltage range: AC720V/10sec.
●Withstand voltage: AC5320V(50/60Hz)/5sec.
(Between electrical circuit and enclosure)
●Insulation resistance: 1000MΩ or more/DC1000V
(Between electrical circuit and enclosure)
●Dimension: 205(L)×152(W)×94(D)mm
●Weight: approx. 1.8kg (battery included)
●Power source: DC12V: Alkaline battery size C(LR14)x 8pcs
●
Current consumption (representative values at 12V of supply voltage)
Range 500V 1000V 2500V 5000V VAC/DC
Output at
short-circuit
For 10 sec after a test is started :
850mA, after that : 150mA 110mA
* at voltage
measurement
When rated
measuring current
is outputted
450mA
/0.5MΩ 500mA /1MΩ 600mA /2.5MΩ 850mA /5MΩ
Output at
open circuit 45mA 50mA 70mA 110mA
On stand-by 25mA 110mA
When backlight
is on Increased by 30mA
Note) Current values in above table are all approximate values.
●Operating time: approx. 10 hours continuous
-
under a load of 100MΩ at 5000V Insulation
resistance range
●Accessories: Line probe: MODEL7165A
Earth cord: MODEL7224A
Guard cord: MODEL7225A
Alkaline size C battery (LR14) x 8pcs
Instruction manual
Hard Case MODEL9159
Pickel Type Prod: MODEL8019
Straight Type Prod: MODEL8254
●Optional accessories: Adaptor for recorder MODEL8302
Line probe with alligator clip MODEL7168

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4. Instrument layout
4-1 Instrument layout
1 LCD display
2 Range switch
3 Test button
4 Back Light button
5 FILTER button
6 DAR/ PI DISP button
7 Line Terminal
8 Earth Terminal
9 Guard Terminal
10 Line Probe (red)
11 Earth Cord (black)
12 Guard Cord (green)
1
4
5
32
6
9 7 12 11 10
8

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4-2 LCD display
1 Insulation resistance
2 Bar graph
3 Voltage
4 Battery mark
5 Voltage warning mark
6 Time
7 DAR mark
8 PI mark
9 DAR/PI value
10 Filter mark
11 DC
12 AC
13 Minus sign
14 Unit
15 Overheat warning mark
52
3
15
1
9
14
4
12
11
13
10
6
7
8

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5. Preparation for measurement
5-1 Checking the battery voltage
(1) Set the Range switch to any position other than “OFF”.
(2) When the battery mark shown at the upper left on the LCD is
last 1 level , the batteries are almost exhausted.
Replace the batteries with new ones to continue further
measurements.
The instrument operates properly even in such a low battery
power condition and it may not affect the accuracy.
When battery mark is empty , the battery voltage is below
the lower limit of the operating voltage. In such a condition, the
accuracy isn’t guaranteed.
Look up Chapter 7. Battery Replacement in this manual, which
describes how to replace the batteries.
5-2 Connecting test leads
Insert the test lead firmly to the connector terminal on the
instrument. Connect the Line Probe(red) to the Line terminal, the
Earth Cord(black) to the Earth terminal and the Guard Cord (green)
to the Guard terminal. (To establish guard is not necessary, you do
not have to connect the Guard cord.)
#DANGER
● Do not press the Test button while the Range switch is at the
Insulation measurement position. High voltages are applied to
the test leads and you may get electrical shocks.

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6. Measurement
6-1 Mains disconnection check (Voltage measurement)
#DANGER
● Do not make measurement on a circuit in which the electric
potential exceeds AC/DC600V (voltage to ground) in order
to avoid getting electrical shock. In addition, do not use this
instrument when the voltage to ground is 600V or higher even
the line voltage is 600V or less.
● Ensure that a measurement is performed at the secondary side
of the circuit breaker when testing the voltages of power lines,
which has a large current capacity, in order to avoid possible
hazard to the user.
● Extra precaution shall be taken to minimize the possibility of
shorting the power line with the metal tip of test lead at voltage
measurement. It may cause personal injury.
● Do not start a measurement with the battery cover removed.
● Connect the Earth cord (black) to the Earth terminal of the
circuit under test.
Voltage can be measured by setting the Range switch on this
instrument to “VAC/DC” position. No need to press the Test button.
KEW3126 has an AC/DC auto-detect circuit and can measure
DC voltage as well. At DC voltage measurement, when applying
positive voltage to the Line Probe (red), positive value is displayed
on the LCD.
Ensure that the circuit breaker of the circuit under test is turned off.
(1)
Connect the Earth Cord (black) to the earth
side of the circuit under test and the Line
Probe (red) to the line side respectively.
(2) Confirm that the voltage displayed on the
LCD is “Lo”. If the display doesn’t show
“Lo”, voltage is applied on the circuit
under test. Check the circuit under test
again and turn off the circuit breaker.

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6-2 Insulation resistance measurement
#DANGER
● Confirm that no electrical charge exists on the circuit under test
before measuring by using a high voltage detector.
● Put on a pair of insulated gloves for high voltage.
● In case the Range switch is set to Insulation resistance range,
high voltage is being applied to the tips of test leads and to
the circuit under test continuously while the Test button is kept
pressed down. Be extremely careful not to get electric shock.
● Do not start measurement with the battery cover removed.
● Never start measurement when thunder rumbling.
● Connect the Earth Cord (black) to the earth terminal of the
circuit under test.
● With the Range switch set to the Insulation resistance range,
live circuit warning symbol appears on the LCD and the audible
warning activates when a voltage of 30V or higher is measured.
KEW3126 doesn’t start a test, even the Test button is pressed
down, if the measuring voltage is 160V or higher: it starts a test
if the measuring voltage is under 160V upon a press of the Test
button. Prior to testing, ensure that the equipment under test is
disconnected from the mains supply and not energized in order
to avoid possible electrical hazards.
This instrument may start a measurement for energized electrical
circuits. Be extremely careful not to get electrical shock.
To check the insulation of electric equipments or electric circuits,
measure their insulation resistances by using this instrument.
Ensure to check the appropriate voltages to be applied to the
equipment under test before starting a measurement.
Note)
● KEW3126 may show unstable readings when the insulation
resistance of the equipment under test is not stable.
● Beep sound may be heard during insulation resistance
measurement. But it is not malfunction.
● It takes time to measure a capacitive load.
● At insulation resistance measurement, positive (+) voltage is
outputted from the Earth terminal and negative (-) voltage is
outputted from the Line terminal.

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Connect the Earth cord to the Earth (ground) terminal.
It is recommended to connect the positive(+) pole to the earth
side when measuring insulation resistance against the ground or
when a part of the equipment under test is earthed.
With this connection, smaller measured value can be obtained
comparing with other way round.
(1) Check the appropriate voltages to be applied to the circuit
under test, and set the Range switch to any desired insulation
resistance range.
(2) Connect the Earth cord (black) to the Earth terminal of the circuit
under test.
(3) Put the tip of the Line probe (red) to the circuit under test.
Then press the Test button. The buzzer sounds intermittently
during measurement when a range other than 500V is selected.
(4) The measured value will be displayed on the LCD, and it
remains displayed on the LCD after a measurement.
#CAUTION
Turn off the breaker of
the circuit under test.
(5) This instrument hasAuto-discharge function.
Keep the test leads connected to the circuit under test and
release the Test button when measurements end. The auto-
discharge function operates to discharge the electrical charges on
the circuit under test. Confirm that the voltage monitor shows 0V.
#DANGER
● Do not touch the circuit under test immediately after testing.
Capacitance stored in the circuit may cause electric shock.
● Leave test leads connected to the circuit and never touch the
circuit until the discharge completes.

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Auto-discharge function
This is a function to discharge capacitance stored in the circuit
under test automatically after testing. Discharge condition can be
checked on the voltage monitor. This function will be canceled
when removing the test leads 2 sec. or more before discharge
completes.
(6) Set the Range switch to “OFF” position, and remove test leads
from the instrument.
Note)
● The voltage warning mark stays on during a measurement and it
blinks when voltages of AC/DC 30V or higher exist on the circuit
under test.
● When measuring low resistances (if currents larger than the
rated current are output) over a long period of time, KEW3126
consumes large power and will overheat. When this happens,
further tests are automatically inhibited and the over-temperature
symbol appears on the display. The instrument must then
be left cool down. Testing shall be resumed when symbol
disappears.
Short-circuit currents at a start of measurement may get lower
when the “ ” symbol appears.
● Depending on the ambient temperature or measured resistances,
the “ ” symbol may appear and interrupt a PI measurement.

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Principle of Insulation Resistance Measurement
Resistance value can be obtained by applying a certain high
voltage to the resistance (insulation resistance) and measuring the
flowing current.
Resistance value = Voltage / Current
(RX = V / I)
6-3 Continuous measurement
Press down and turn the Test button clockwise to lock it to perform
a continuous measurement of insulation resistance. After testing,
turn the button counterclockwise and set it to the initial position.
#DANGER
● Be extremely careful not to get electric shock as high voltage is
present on the tip of test leads continuously.
LINE(-)
EARTH(+)
RESISTANCE VALUE: RX
CURRENT: I
VOLTAGE: V

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6-4 DAR/PI Measurement function
1. PI – Polarization index
This is to check a temporal increase of leakage currents flowing on
insulations and to confirm leakage currents aren’t increased as time
passes.
PI is usually determined by the insulation resistances measured 1
min and 10 min after a measurement is started. PI is dependent
on the shape of insulations and influenced by moisture absorption,
therefore, a check of PI is important to diagnosis the insulation of
cables.
Insulation resistance
(10 min after a start of test)
Insulation resistance
(1 min after a start of test)
PI =
PI 4 or more 4 −2 2.0 −1.0 1.0 or less
Criteria Best Good Warning Bad
2. DAR - Dielectric Absorption Ratio
DAR measurement is almost same to PI measurement in a sense
that they test the time course of insulation. The only difference is
that DAR measurement can get result faster than the other.
Insulation resistance
(1 min after a start of test)
Insulation resistance
(15 or 30 sec min after a start of test)*1
DAR =
DAR 1.4 or more 1.25 −1.0 1.0 or less
Criteria Best Good Bad
Note1: DAR time is selectable: 15 or 30 sec.
How to select:
(1) Keep the DISP button pressed down and rotate the Range
switch to power on KEW3126. (DAR mark blinks on the LCD.)
(2) Press the DISP button to switch 15 sec and 30 sec displayed at
the lower left on the LCD. Select the desirable one.

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(3) Press the FILTER button and confirm the selection.
Selected DAR time is saved and kept after the instrument is
powered off.
To check the time currently selected, follow the step (1)
described as above.
3. How to measure DAR/ PI
DAR and PI are measured automatically at normal continuous
measurement of insulation resistances. Set the Range switch to
any range and measure the test object continuously.
- 1 min after a start of continuous measurement:
LCD shows DAR value.
- 10 min after a start of continuous measurement:
LCD shows PI value.
When DAR/PI values are displayed as “no”:
DAR and PI values are determined by the methods 1. and 2. as
described above, therefore, they are displayed as “no” when the
measured insulation resistances fall under any of following cases.
(1) measured value is “0.0MΩ”
(2) measured value is “OL”
* “OL” is displayed when the measured value exceeds the upper
limit of the measuring range at each insulation resistance range.
Range Upper limit
500V 999MΩ
1000V 1.99GΩ
2500V 99.9GΩ
5000V 1000GΩ