Ground Clamp Resistance Meter
Instruction Manual
61-920
Contents
1. Safety warnings ....................................................................................... 1
2. Features................................................................................................... 3
3. Specifications .......................................................................................... 4
4. Instrument layout..................................................................................... 6
5. Measurement theory ................................................................................ 7
6. Preparation for measurement .................................................................. 9
7. Measuring procedure ............................................................................ 10
7-1 Normal measurement of current .................................................. 11
7-2 Measurement of balance leakage current ..................................... 11
7-3 Measurement of earth resistance. ................................................ 12
8. Other functions ...................................................................................... 14
8-1 Auto power-off feature .................................................................14
8-2 Data hold feature.......................................................................... 14
8-3 Continuity Buzzer function ........................................................... 14
1. Safety Warnings
This instrument has been designed, manufactured and tested according to IEC61010
Safety Requirements for electronic measuring apparatus, and calibrated in accordance with
practices using equipment that is calibrated to standards traceable to the National Institute for
Standards and Technology (NIST). This instruction manual contains warnings and safety
procedures which must be observed to ensure safe operation of the instrument and
maintain it in a safe condition. These operating instructions must be read prior to using
the instrument.
WARNING
1. Use of personal protective gear, such as insulating gloves, boots, glasses, is
recommended even if the equipment is properly operated and grounded.
2. Safety is the responsibility of the operator.
3. Ensure meter is in proper working order before using. Visually inspect meter for
damage.
4. Use extreme caution when using the instrument around energized electrical
equipment.
5. Do not attempt to use the ground tester to twist or pry the ground electrode or
ground wire away from the equipment being grounded.
6. All metal objects or wires connected to the electrical system should be assumed
to be lethal until tested. Grounding systems are no exception.
7. Do not use without the battery and back case properly installed.
8-4 Backlight feature .......................................................................... 14
8-5 Memory feature ........................................................................... 15
9. Battery replacement ............................................................................... 16
10. Service .................................................................................................. 17
11. Warranty ................................................................................................ 18
DANGER
WARNING
CAUTION
Following symbols are used on the instrument. Attention should be paid to each
symbol to ensure safety.
This symbol indicates that the user must refer to the explanations in the instruction
manual.
This symbol indicates that the instrument is protected by double or reinforced
insulation.
This symbol indicates that this instrument can clamp on bare conductors.
This symbol indicates AC.
~
: is reserved for conditions and actions that are likely to cause
serious or fatal injury
: is reserved for conditions and actions that can cause serious or
fatal injury
: is reserved for conditions and actions that can cause injury or
instrument damage.
DANGER
• Do not use the instrument on a circuit where electrical potential exceeds 300VAC.
• Do not use the instrument during an electrical storm or in wet weather.
• Do not use the instrument in the presence of flammable gas, dust or vapor.
• Wear insulated protective gear to avoid electrical shock.
• Use caution where the equipment under test has exposed metal parts.
• Never attempt to use the instrument if its surface or your hands are wet.
• Do not use meter if it operates abnormally as protection may be impaired.
• Do not use around explosive gas, dust, vapor, or in damp or wet environments. Do not
submerge or expose the meter to water and do not use if the meter has ever been exposed to
water or other fluids.
• Do not exceed the maximum allowable input of any measuring range.
• Do not use the instrument on a circuit over 30AAC. If “ “ is displayed on the LCD,stop
measurement immediately. Remove meter from conductor.
• Never open the battery cover during a measurement.
• When the transformer jaws are worn to the wear line (see the figure below), stop the use of
the instrument.
WARNING
• Do not use the instrument if any abnormal conditions, such as a broken cover or exposed
metal parts are present on the instrument.
• Do not install substitute parts or make any modification to the instrument.
• Do not try to replace the batteries if the surface of the instrument is wet.
• Always turn off the instrument before opening the battery cover for battery replacement.
• Always be sure to keep your fingers and hands behind the safety barrier. (see figure below) ....
Otherwise, user may be exposed to the danger of electrical shock.
• Do not submerge or expose the meter to water and do not use if the meter has ever been
exposed to water or other fluids.
2. Features
The 61-920 is a digital clamp-on ground resistance tester. The instrument can measure
the ground resistance by simply clamping around the ground conductor, ground rod or
equipment ground conductor.
The 61-920 also measures leakage AC current up to 30AAC.
• Wide measuring range (Auto-ranging)
Ground resistance Max. 1200 Min. resolution 0.01Ω
AC current Max. 30A Min. resolution 0.1mA
• Noise check function senses current on the ground electrode or ground wire and
displays NOISE on the LCD display.
• True RMS feature accurately measures AC current even with distorted waveforms due to
harmonics.
• Auto power-off feature powers the meter down automatically after 10 minutes of
non-use to conserve battery power.
• Data hold feature is used to capture and hold a reading in the LCD display.
• Continuity buzzer function provides an audible warning to the user when the
measurement result is 10Ω or less.
• Backlight feature illuminates the display for working in dimly lit areas.
• Memory save feature records and displays the measurement result.
• Complies with IEC61010-1: 2001 (CAT.IV 300V Pollution degree 2),
IEC61010-2-032: 2002 safety standards.
• This instrument is protected by double or reinforced insulation
|>
CAUTION
• Press the Function button and confirm the appropriate function is selected before starting a
measurement.
• Remove the batteries for storage or if the meter will not be used for longer than one month.
Battery leakage will compromise the safety of the meter and cause damage to internal
components.
• Do not expose the instrument to the direct sun, high temperatures and humidity or dew.
3. Specifications
Function Range Resolution
20Ω 0.01Ω 0.00 ~ 20.99Ω ±1.5%±0.05Ω
Earth
200Ω 0.1Ω
resistance
(Auto-ranging)
1200Ω
1Ω
10Ω 600 ~ 1260Ω —
AC current (ACA)
(sine wave)
(50Hz/60Hz)
(Auto ranging)
• Crest factor <2.5 Accuracy at sine wave ±1% (50Hz/60Hz, peak value shall not exceed 60A)
• In the following cases, zero will be displaed on the LCD: At20Ω range of Earth resistance function: 0.04Ω
or less.
• Auto ranging shifts to upper range when the input exceeds 105% of the selected range, and shifts to the
lower range when the input falls under 80% of the lower range.
100mA 0.1mA 0.0 ~ 104.9mA ±2%±0.7mA
1000mA 1mA 80 ~ 1049mA
10A 0.01A 0.80 ~ 10.49mA
30A 0.1A 8.0 ~ 31.5AmA
• Operating system Earth resistance function: Constant voltage injection, Current
detection, (Frequency: Approx.
2400Hz) Dual Integration
AC current function: Successive Approximation
(True-RMS)
• Display Liquid crystal display with a maximum count of 2099
• Over-range indication “OL” is displayed when input exceeds the upper limit of a
measuring range
• Response time Earth resistance function: Approx. 7 seconds
AC current function: Approx. 2 seconds
• Sample rate Approx. once per second
• Location for use Altitude 2000m or less, Indoor/ outdoor use
• IP protection degree IP40
• Temperature & 75°F±5%/Relative humidity 85% or less
humidity range (no condensation)
(guaranteed accuracy)
• Operating temperature 14°F ~ 104°F/Relative humidity 85% or less (no condensation)
& humidity range
• Storage temperature -4°F ~ 140°F/Relative humidity 85% or less
& humidity range (without batteries, no condensation)
• Power source (4) batteries AA
• Current consumption Approx. 50mA (max. 100mA)
• Measurement time Approx. 12 hours (when alkaline batteries are used),
Approx. 24 hours (when alkaline battery is used)
• Auto power-off Turns power off after 10 minutes of non-use.
Measuring
range
Accuracy
16.0 ~ 9.99Ω ±2%±0.5Ω
100.0 ~ 209.9Ω ±3%±2Ω
160 ~ 399Ω ±5%±5Ω
400 ~ 599Ω ±10%±10Ω
±2%
• Applicable standards IEC61010-1: 2001 (CAT. IV 300V Pollution degree 2) IEC61010-2-032:
2002 IEC61326: 2000 (EMC standard)
• Electrostatic discharge Performance criteria B
immunity
• Withstand voltage AC5320Vrms/ 5 seconds
Between the Transformer jaws fitted parts and Case enclosure (except
for jaws)
• Insulation resistance 50MΩ or more at 1000V
Between the Transformer jaws fitted parts and Case enclosure (except
for jaws)
• Conductor size Approx. 1.25” in diameter max.
• Dimension 9.7”(L) x 4.7”(W) x 2.1”(D)
• Weight Approx. 1.7 lbs (including batteries)
• Accessories Battery AA : 4 pcs.
Instruction manual : 1 pc.
Resistor for operation check : 1 pc.
Hard case : 1 pc.
<Supplemental remarks>
Effective value (RMS)
Most alternating currents and voltages are expressed in effective values, which are also referred
to as RMS (Root-Mean-Square) values. The effective value is the square root of the average of
square of alternating current or voltage values. Many clamp meters using a conventional
rectify- ing circuit have “RMS” scales for AC measurement. The scales are calibrated in terms of
the effective value of a sine wave through the clamp meter responding to the average value. The
cali- bration is done with a conversion factor of 1.111 for sine wave, which is found by dividing
the effective value by the average value. These instruments are therefore in error if the input
voltage or current has some other shape than a sine wave.
CF (Crest Factor) is found by dividing the peak value by the effective value.
Examples:
Sine wave: CF=1.414 Square wave with a 1: 9 duty ratio: CF=3
4. Instrument Layout
• Feature callouts
1
Transformer jaw
Lever
2
Backlight button
3
Switches on/off the backlight
4
Function button
Switches ACA/Earth
resistance function
5
Memory mode button
Records the measured value
with a data number
6
Data hold button
Holds the indicated value.
Release the held value
7
Power button
Turns the meter on/off
8
Display unit (LCD)
Cursor button (UP)
9
Selects data number to save the
measured value or to view the
measured data in memory
10
Cursor button (DOWN)
Selects data number to save the
measured value or to view the
measured data in memory.
Save button
11
Saves the measured value.
• Marks to be displayed on the LCD
Displayed when saving the measured value
MEM
or when instrument is in memory mode
Displayed when batteries are exhausted
Displayed in Earth resistance function
when Transformer jaws are not properly
closed.
Displayed in Earth resistance function
with current or noise which affects the
measured value.
Displayed when data hold functions
activated
Displayed when ACA function is selected
Displayed when instrument is in continuity
mode at Earth resistance function
5. Measurement Theory
This instrument can measure the earth resistance to earth in a multi-earthed system. Let’s
regard earth resistance under test as Rx, and the other earth resistances as R1, R2, …Rn.
1
2
3
4
5
11
Data number
1 to 100
Measured value Unit
6
7
8
9
10
Of these earth resistances, R1, R2, …Rn can be considered connected in parallel and can
be regarded as a combined resistance Rs. The Rs can be regarded small enough against Rx
since combined resistance consists of several resistances. Following is an equivalent circuit
diagram of this scenario.
By applying the Voltage (V) to the circuit from the transformer jaw (CT1), current I is flowing
in relation to the earth resistance. R can be determined by calculation after measuring the
current with the other transformer jaw (CT2). In this case, R displayed in this meter can be
regarded as Rx because Rs can be regarded small enough against Rx.
6. Preparation for Measurement
CAUTION
This instrument performs self-calibration for about 3 seconds when it is turned on. (″ ″ is
displayed on the LCD.) Do not clamp onto any conductor or open the jaws during this procedure.
Inaccurate measurements may occur.
Resistor for operation check
CAUTION
This meter cannot support the measurement for the locations with the following earth systems.
• Single-earth that is not connected to the other earths (lighting rod, etc.)
• Earth on which a current over 2AAC is measured
• Earth with earth resistance over 1200Ω
1Ω loop 1Ω loop
Resistor for operation check
1Ω
10Ω
Allowable range
0.93 ~ 1.07
9.75 ~ 10.25
7. Measuring Method
DANGER
• Never make measurements on a circuit in which the electrical potential exceeds 300VAC.
• Transformer jaws are made of metal and their tips are not completely insulated. Guard against
the possible shorting where the equipment under test has exposed metal parts.
• Do not use the instrument in the presence of flammable gas, dust or vapor.
• Never make measurements with battery cover removed.
• Do not measure currents over 30A. Transformer jaws may overheat, causing a fire, deforming
of plastic parts or degrading of insulation. If “ “ is displayed on the LCD, stop measuring
immediately and remove the instrument from the conductor under test.
DANGER
• Take sufficient care not to apply shock, vibration or excessive force to the jaw tips. Otherwise,
precisely adjusted transformer jaws will be damaged.
• This instrument performs self-calibration for about 3 seconds when it is turned on. (“ “ is
displayed on the LCD.) Do not clamp onto any conductor or open the jaws during this
procedure. Inaccurate measurements may occur.
• For accurate measurements, ensure that the jaw tips are free from foreign substances, align
properly, and fully close. Do not release the jaw trigger abruptly or attempt to close the
transformer jaws by applying external force.
• The jaw opening allows for a maximum conductor diameter of 1.25”. Accurate measurements
cannot be made on a larger conductor since the jaws will not fully close. Never attempt to
apply excessive force to open or close the jaws.
• When measuring large current, (up to 30 amps), the transformer jaws may buzz. This is
normal and has no effect on the instrument’s performance or safety.
• The instrument’s transformer jaws are highly sensitive. Because of the characteristics of the
transformer jaws, it is impossible to eliminate the interference of an external magnetic field
completely. If there is a large magnetic field nearby, the display will not zero before clamping
onto a conductor. In this case, use the meter at a location as far as possible from the magnetic
field. Typical generators of magnetic fields include conductors with large currents flowing,
motors, electromagnetic equipment, integrated watt meters.
7.1 Normal Measurement of current
• Press the Function button and select the ACA function.
• Confirm the displayed unit is “ mA”, and the “ MEM” mark is not displayed at the upper left
corner of the LCD.
• Press the lever to open the transformer jaws and close them over a single conductor.
• The measured current value is then displayed on the LCD. (Earth leakage current that flows ....
through a ground wire can also be measured by this method.)
7.2 Measurement of Balanced leakage current
• Press the Function button and select the ACA function.
• Confirm the displayed unit is “ mA”, and the “ MEM” mark is not displayed in the upper left
corner of the LCD.
* Clamp onto all conductors except the earthed wire.
* The measured current value is displayed on the LCD.
Single-phase 2-wire system
In 3-wire system with neutral, clamp
onto all 3 wires.
Three-phase 3-wire system
In 4-wire system with neutral, clamp
onto all four wires.
7.3 Measurement of earth resistance Earth resistance measurement of a pole grounding electrode.
CAUTION
• Follow the procedure described in “7-1 Normal measurement of current” and measure the
current flowing on the earthed wire prior to the measurement of earth resistance. If “ “
is displayed in the upper right of the LCD, it means there is too much interference to obtain
an accurate reading. To avoid such inaccuracies, reduce the current flowing on the ground
wire by turning off the device causing this current to flow.
• Measurements cannot be made for multi-ground systems or when the ground resistance
under test is smaller than the other ground resistances.
• If the jaws of the instrument are not properly closed, the “ “ mark will be displayed.
Close the transformer jaws properly to continue with the measurement.
• The response time is about 7 seconds on the earth resistance function. Note the reading after
it becomes stable.
• Measurement procedure
- Press the Function button and select the Earth resistance function.
- Confirm that the displayed unit of measure is “ Ω “ and “ MEM “ is not displayed in the
upper left corner of the LCD.
- Press the lever to open the transformer jaws and close them around the ground wire
under test.
- The measured resistance value is displayed on the LCD.
<Noise check function>
When in the earth resistance function, the “ “ symbol is displayed on the LCD. Under the
following scenarios, noise can affect the measurement accuracy:
1. The current flowing on the ground wire is exceeding the following values:
Earth resistance measurement of a ground electrode in a street lighting system.
Range of Earth Resistance Function
20Ω
200Ω / 1200Ω
Allowable current value
2A or less
400mA or less
2 The current flowing on the ground wire includes a harmonic waveform.
<Jaws check function>
The “ “ symbol is displayed when the transformer jaws of the instrument are not properly closed.
Measurement is stopped while this symbol is displayed on the LCD.
Earth resistance measurement of a grounding electrode in a lighting protection
system.
8. Other Functions
8.1 Auto power-off function
This is a function to conserve battery power when the instrument is accidentally left on. The meter
automatically turns off 10 minutes after the last button operation. If auto power-off occurs, press the
Power button to return power to the meter.
The buzzer sounds before the instrument turns off.
To disable the auto power-off function, follow the procedure below.
(1) Turn on the instrument by pressing the Power button with the Data hold button
depressed. Then release the Power button and Data hold button.
(2) The instrument should now display ” “ in the LCD for about 1 second to confirm that
the auto power-off function is disabled.
To enable the auto power-off function again, turn the meter off and on without depressing the Data hold
button.
8-2 Data hold function
This feature freezes the indicated value on the display. When the Data hold button is pressed
once, the indicated value on the LCD is held even though current under test varies. The “ “ mark
is shown in the upper right corner of the LCD. To exit the Data hold mode, press the Data hold button
again. The “ “ mark should disappear from the display.
When the Auto power-off feature engages to turn the meter off, any value being held in the
display with the Data hold feature is lost.
8-3 Continuity Buzzer function
This function provides an audible indication to the user when the measured earth resistance is 10Ω or
less. To enable the continuity buzzer function, press and hold the button when in the ohms mode
for at least 2 seconds. (The symbol is displayed in the lower left of the LCD.) The Buzzer sounds
when the measured earth resistance is 10Ω or less. To disable the buzzer function, press the “ “
button again. The “ “ symbol should disappear.
8-4 Backlight feature
This feature illuminates the display background to allow viewing in dimly lit areas. To turn on the
backlight, press the backlight button while the meter is turned on. To turn off the backlight, press
the backlight button again. The backlight is automatically switched off after 1 minute to conserve
battery power.
POWER
H
DATA
HOLD
DATA
HOLD
H
8.5 Memory function
This function saves and displays several measurement results.
• Saving the measurement results
(1) Any data number (between 1 and 100) can be selected with the cursor button or
while on the ACA or ground resistance function. Holding the cursor button down allows you
to scroll through the numbers faster.
(2) To save the measurement result being displayed on the LCD, press the button. The
result is then saved to the selected data number. (“MEM” indicator is displayed for about
1 second.)
The new data point overwrites any previous data point on the selected data number. After
saving a data point, the data number automatically advances to the next available data
number so the next measured value can be saved. When saving data while the data hold
function is activated, the reading which is being held on the LCD will be saved.
• Recalling the measurement results in memory
To activate the memory function, press the memory mode button . The “MEM” symbol
MEM
MODE
is displayed on the LCD. Pressing the cursor or changes the data number displayed on
the LCD, and the measurement result in memory is displayed accordingly.
To disable the memory mode, press the Memory mode button again or press the
button. The “MEM” symbol should disappear from the display. When “ - - - - “ is displayed
with a data number, it means no measurement result is saved.
• Clearing the measurement results in memory
To clear an individual measurement result, press the button and the button together.
MEM
WRITE
The message “ “ is displayed on the LCD for about 2 sec. The measurement result on the
selected data number is cleared. The indication on the LCD becomes “ - - - - “.
To delete all measurement results.
(1) Press the button when the instrument is off while depressing the button
and button. Release the button only.
MEM
MODE
POWER
POWER
(2) The instrument should turn on and display: “MEM”, “ “ and “ “ for about
2 sec. All the previously stored data is now deleted.
MEM
MODE
MEM
WRITE
MEM
WRITE
9. Battery replacement 10. Service
If the instrument should fail to operate correctly, please go to the link below to fill out a service request:
WARNING
• In order to avoid possible shock hazard, remove the meter from the conductor under test,
remove test leads from the meter, and turn off the instrument before removing the battery
cover.
CAUTION
• Do not mix new and old batteries. Never use different types of batteries at the same time.
• Install batteries in the orientation as shown inside the battery compartment, observing correct
polarity.
When the battery voltage warning symbol “ “ is displayed on the upper left of the LCD, replace
the batteries.
(1) Remove the meter from all measuring sources.
(2) Turn off the meter.
(3) Loosen the battery cover-fixing screw on the back of the instrument.
(4) Remove the battery cover.
(5) Replace the (4) AA batteries with fresh ones noting the proper orientation illustrated inside
the battery compartment to ensure correct polarity.
(6) Re-install the battery cover and tighten the screw.
http://www.idlim.net/support/testerRMA.action
For repair, the calibration plate used for proper operation check must be returned with the meter. Before
returning the instrument, make sure:
a) Operating instructions have been followed.
b) Battery has been checked.
You may also call the Technical Service Hotline at 877-201-9005.
11. TWO YEAR LIMITED WARRANTY
This tester is warranted to the original purchaser against defects in material and
workmanship for a period of two (2) years from date of purchase. With proof of purchase
from an authorized IDEAL distributor, a defective tester will be repaired or replaced with the
same product or a functionally equivalent product, at the option of IDEAL INDUSTRIES,
INC. during the warranty period, subject to verification of the defect or malfunction.
Warranty does not cover consumables such as fuses, batteries, and excludes defects
caused by leakage from batteries, abuse, mishandling, dropping, ordinary wear and tear,
misuse, neglect, unauthorized repair, improper use, alterations, accidents or any causes
beyond IDEAL’s reasonable control. Consequential or incidental damages are not
recoverable under this warranty. Some states do not allow the exclusion or limitation of
incidental or consequential damages, so the above limitation or exclusion may not apply to
you. This LIMITED WARRANTY gives you specific legal rights, which vary from state to
state. This warranty constitutes the sole and exclusive remedy of the purchaser and the
exclusive liability of IDEAL, and is in lieu of any and all other warranties, and expressly
disclaims all other warranties, implied, or statutory as to merchantability, fitness for
purpose sold, description, quality productiveness, or any other matter. No agent,
distributor or other supplier has the authority to modify or amend this warranty or make
other representations or warranties other than those contained in this warranty without
express written authorization from IDEAL. For warranty service, call IDEAL customer
service at 1-800-435-0705.
IDEAL INDUSTRIES, INC.
Sycamore, Illinois, USA 60178
800-435-0705 Customer Assistance
idealind.com
ND 5417-2
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