Ideal 61920 User Manual
#61-920
Ground Clamp Resistance Meter
Instruction Manual
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
8-4 Backlight feature ................................................................................................14
8-5 Memory feature ..................................................................................................15
9. Battery replacement ..................................................................................................16
10. Service ......................................................................................................................17
11. Warranty....................................................................................................................18
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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.
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.
Following symbols are used on the instrument. Attention should be paid to each symbol to
ensure your 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.
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DANGER
• Do not use the instrument on a circuit where electrical potential exceeds 300VAC.
• Do not use the instrument during an electrical storm.
• 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 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. Return the instrument to:
IDEAL INDUSTRIES, INC.
Attn: Repair Department
1000 Park Avenue
Sycamore, IL 60178
• 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.
CAUTION
• Press the Function button and confirm the appropriate function is selected before starting a
measurement.
• Do not expose the instrument to the direct sun, high temperatures and humidity or dew.
• Press the Power button and turn off the instrument after use. When the instrument is not in use for
a long period of time, place it in a storage after removing the batteries.
• Use a damp cloth with mild detergent for cleaning the instrument. Do not use abrasives or solvents.
• Do not drop. Precisely adjusted transformer jaws will be damaged.
• Keep jaw tips clear of debris.
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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. 1200Ω 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 .
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3. Specifications
• Measuring range and accuracy
Function Range Resolution Measuring range Accuracy
Earth 20Ω 0.01Ω 0.00
~ 20.99Ω ±1.5%±0.05Ω
resistance
200Ω 0.1Ω
16.0 ~ 99.9Ω ±2%±0.5Ω
(Auto-ranging) 100.0 ~ 209.9Ω ±3%±2Ω
1Ω
160 ~ 399Ω ±5%±5Ω
1200Ω 400 ~ 599Ω ±10%±10Ω
10Ω 600 ~ 1260Ω —
AC current (ACA) 100mA 0.1mA 0.0 ~ 104.9mA ±2%±0.7mA
(sine wave) 1000mA 1mA 80 ~ 1049mA
(50Hz/60Hz) 10A 0.01A 0.80 ~ 10.49mA ±2%
(Auto ranging) 30A 0.1A 8.0 ~ 31.5AmA
* Crest factor <2.5 Accuracy at sine wave +1% (50Hz/60Hz, peak value shall not exceed 60A)
* In the following cases, zero will be displayed on the LCD.
At 20Ω 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.
• 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
& humidity range (no condensation)
• 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 manganese battery is used),
Approx. 24 hours (when alkaline battery is used)
• Auto power-off Turns power off after 10 minutes of non-use.
• 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 rectifying 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 calibration 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
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4. Instrument Layout
• Feature callouts
Transformer jaw
Lever
Backlight button
Switches on/off the backlight
Function button
Switches ACA/Earth resistance function
Memory mode button
Records the measured value with
a data number
Data hold button
Holds the indicated value.
Release the held value
Power button
Turns the meter on/off
Display unit (LCD)
Cursor button (UP)
Selects data number to save the
measured value or to view the
measured data in memory
Cursor button (DOWN)
Selects data number to save the
measured value or to view the
measured data in memory.
Save button
Saves the measured value.
Data number
1 to 100
UnitMeasured value
• Marks to be displayed on the LCD
Displayed when saving the measured value 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 cur-
rent 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
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5. Measurement Theory
This instrument can measure the earth resistance to earth in multi-earthed system. Let's regard earth resistance under test as Rx, and the other earth resistances as R1, R2, …Rn.
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.
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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.
CAUTION
This meter cannot support the measurement for the locations with the following earth systems.
• Single-earth that is not connected to other earths (Lightning rod, etc.)
• Earth on which a current over 2AAC is measured.
• Earth with earth resistance over 1200Ω.
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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.
(1) Check the battery voltage.
When the LCD display is blank, press the Power button and turn on the meter. Battery
voltage is sufficient when the display is legible and the " "mark is not displayed on the LCD.
Otherwise, replace the batteries to ensure accurate measurements and proper storage of data points.
(2) Verify the correct measurement of earth resistance. Clamp the meter around the calibration plate to
ensure proper operation. If the displayed value is outside the specified accuracy on the plate, send the
instrument with the calibration plate back to IDEAL for repair.
Resistor for operation check Allowable range
1Ω 0.93 ~ 1.07
10Ω 9.75 ~ 10.25
Power
1Ω loop 10Ω loop
Resistor for operation check
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CAUTION
• 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 close the jaws.
• When measuring large current, 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 wattmeters.
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.
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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.
A/Ω
A/Ω
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 4 wires.
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7-3 Measurement of earth resistance
A/Ω
NOISE
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:
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.
NOISE
Range of Earth Resistance Function Allowable current value
20Ω 2A or less
200Ω / 1200Ω 400mA or less
Earth resistance measurement of a pole grounding electrode.
Earth resistance measurement of a ground electrode in a street lighting system.
Earth resistance measurement of a grounding electrode in a lightning protection system.
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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 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.
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Power
DATA
HOLD
DATA
HOLD
H
H
A/Ω
A/Ω
Page 17
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 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. 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.
(2) The instrument should turn on and display: "MEM", " " and " " for about 2 sec.
All the previously stored data is now deleted.
MEM
WRITE
MEM
MODE
MEM
MODE
MEM
MODE
A/Ω
MEM
WRITE
MEM
WRITE
Power
Power
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9. Battery replacement
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.
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.
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