Earth Ground Testers

he Fluke 1625-2 offers you simpler, faster earth ground tests than ever before. The 1625-2 offers internal memory storage up to 1500 records, accessible via USB port for rapid data transfer and viewing of results. This earth ground tester also gives you world-class accessories that take the tedium out of earth ground testing. New wire reels speed up setup and tear down time as much as 50%. Heavy duty stakes can be hammered into dry, hard soil. And new color-coded wires make setup simple and help eliminate mistakes.

Stakeless Testing

The Fluke 1625-2 earth ground tester is able to measure earth ground loop resistances using only clamps. With this test method, two clamps are placed around the earth ground rod and each are connected to the tester. No earth ground stakes are used at all. A known, fixed voltage is induced by one clamp and the current is measured using the second clamp. Then the tester automatically determines the resistance of the earth ground rod. This test method only works if a bonded earth ground system exists for the building or structure under test, but most are. If there is only one path to ground, like at many residential applications, the Stakeless method will not provide an acceptable value and the Fall of Potential test method must be used.

With Stakeless testing, the earth ground rod does not need to be disconnected – leaving the bonded earth ground system intact during test. Gone are the days of spending time placing and connecting stakes for each earth ground rod on your system – a major time saver. You can also perform earth ground tests in places you’ve not considered before: inside buildings, power pylons, or anywhere you don’t have access to soil.

The Most Complete Tester

The Fluke 1625-2 is a unique earth ground tester that can performs all four types of earth ground measurement:

  • 3- and 4-Pole Fall-of-Potential (using stakes)
  • 4-Pole Soil Resistivity testing (using stakes)
  • Selective testing (using 1 clamp and stakes)
  • Stakeless testing (using 2 clamps only)

Memory Internal memory storage up to 1500 records accessible via USB port
Measuring function Interference voltage and frequency, earthing resistance 3- and 4-pole with/without clip-on current transformer, resistance 2-pole with ac, 2- and 4-pole with dc
Display 4 digit (2999 Digit) – 7 segment liquid crystal display, with improved visibility
Operation Central rotary switch and function keys
Temperature Range
Operating temperature -10 °C to 50 °C (14 °F to 122 °F)
Storage temperature -30 °C to 60 °C (-22 °F to 140 °F)
Temperature coefficient ± 0.1 % of reading/°C <18 °C >28 °C
Type of protection IP56 for case, IP40 for battery door according to EN60529
Max voltage Warning – socket “clamp” to socket E, ES, S or H
Urms = 0 V
Sockets E, ES, S or H to each other in any combination, max. Urms = 250 V (pertains to misuse)
Safety Protection by double and/or reinforced insulation. Max. 50 V to earth per IEC61010-1. 300V CAT II, Pollution degree 2
Quality standard Developed, designed and manufactured to comply with DIN ISO 9001
External field influence Complies with DIN 43780 (8/76)
Auxiliary power 6 x 1.5 V alkaline (IEC LR6 or type AA)
Battery life span With IEC LR6/type AA: typ. 3,000 measurements (RE+RH ≤ 1 kΩ)
With IEC LR6/type AA: typ. 6,000 measurements (RE + RH > 10 kΩ)
Dimensions (WxHxD) 250 mm x 133 mm x 187 mm (9.75 in x 5.25 in x 7.35 in)
Weight ≤ 1.1 kg (2.43 lb) without accessories 7.6 kg (16.8 lb) incl. accessories and batteries in carrying case
Case material Polyester
Measurement of Interference Voltage dc + ac (UST)
Measuring limits of error: method Full wave rectification
Measuring range 1 V to 50 V
Display range 0.0 V to 50 V
Resolution 0.1 V
Frequency range dc/ac 45 Hz to 400 Hz sine
Accuracy ± (5 % of rdg + 5 digit)
Measuring sequence Approx. 4 measurements/s
Internal resistance Approx. 1.5 MΩ
Max. overload Urms = 250 V
Measurement of Interference Frequency (F )
Measuring limits of error: method Measurement of oscillation period of the interference voltage
Measuring range 6.0 Hz to 400 Hz
Display range 16.0 Hz to 299.9 Hz to 999 Hz
Resolution 0.1 Hz to 1 Hz
Range 1 V to 50 V
Accuracy ± (1 % of rdg + 2 digit)
Earthing Resistance (RE)
Measuring method Current and voltage measurement with probe as IEC61557-5
Open circuit voltage 20/48 V, ac
Short circuit current 250 mA ac
Measuring frequency 94, 105, 111, 128 Hz selected manually or automatic. (AFC) 55 Hz in function R*
Noise rejection 120 dB (16 2/3 , 50 , 60, 400 Hz)
Max. overload Urms = 250 V

Earth Ground Tester for resistance measurement

The Fluke 1621 is an easy-to-use earth ground tester. For ground resistance testing, the 1621 is the first line of defense in detecting reliable ground connections. The unit features basic ground testing methods including 3-pole Fall-of-Potential as well as 2-pole ground resistance tests. Its convenient size, rugged holster, and large, clear LCD display make it an ideal field earth ground tester, for most electrical grounding work environments. With a simple user interface and intuitive functionality, the Fluke 1621 is a handy grounding tool for electrical contractors, utility test engineers, and earth ground specialists.

  • 3-pole Fall-of-Potential earth testing for basic measurements
  • 2-pole resistance measurements for added versatility
  • Easily capture values with single-button operation
  • Ensure accurate measurements with automatic ‘noise’ voltage detection
  • Hazardous voltage warning offers increased user protection
  • Clearly read and record data with a large, backlit display
  • Rugged holster and design for tough work environments
  • Portable size allows for easy transportation
  • Instantly be alerted to measurements outside of your set limit, when you use the adjustable limit setting
  • 600 V Cat II

Measuring functions
 3-pole earth ground resistance, 2-pole ac resistance of a conductor, Interference voltage
Intrinsic error
 Refers to the reference temperature range and is guaranteed for one year
Measuring rate
 2 measurements/second
 One 9 volt alkaline (LR61)
Battery condition
 LO-BAT is displayed if voltage drops below 6.5 V
Between jacks H/C2 and E/C1:  250 Veff maximum (effective voltage)
Between jacks S/P2 and E/C1:  250 Veff maximum
Climatic class
 VDE/VDI 3540 RZ (conforming to KWG as per DIN 40040, 4/87)
Temperature performance[2]
Working:  -10 °C to +50 °C (+14 °F to +122 °F)
Operating:  0 °C to +35 °C (+32 °F to +95 °F)
Storage:  -20 °C to +60 °C (+68 °F to +140 °F)
Reference:  +23 °C ± 2 °C (+73 °F ± 4 °F)
Temperature coefficient
 ± 0.1 % of range per degree Kelvin
 IEC/EN 61010-1, 600 V CAT II, pollution degree 2
 113 mm x 54 mm x 216 mm (4.5 in x 2.1 in x 8.5 in), including holster
 850 g (1.9 lb), including standard accessories, volume approximately 600 cm3
 [1]If the tester is not going to be used, or is being stored for a long period, remove the battery and store separately from the tester to avoid damage from battery leakage.
 [2]The four temperature ranges for the tester exists to satisfy European Standards requirements; the instrument can be used over the full working temperature range by using the temperature coefficient to calculate accuracy at the ambient temperature of use.
Electrical specifications
Maximum deviations:
E1 Influence factor  Position
E1 Deviation influence  0 %
E2 Influence factor  Supply voltage
E2 Deviation influence  0 %
E3 Influence factor  Temperature E3
E3 Deviation influence  2.3 %
E4 Influence factor  Serial interference voltage (20 V)
E4 Deviation influence  0.6 %
E5 Influence factor  Probe- and auxiliary probe resistance
E5 Deviation influence  10 %
Test voltage
 3.7 kV
Protection type
 IP 40; IEC/EN 60529
Electromagnetic compatibility
 Emission: IEC/EN 61326 Class B
 Immunity: IEC/EN 61326 Annex C
RE resistance measurement
Measuring method  Current-voltage measurement with improved cross-talk attenuation, no compensation of measuring lead resistance, with probe (3-pole) or without probe (2-pole), as per IEC/EN 61557-5
Open circuit voltage  23 to 24 V ac
Short circuit current  > 50 mA ac
Measuring frequency  128 Hz
Maximum permissible overload  250 Veff
Measuring time
 8 seconds (average from when START is pressed)
Limit input
 Tester retains set value even if instrument is turned off (assuming battery power supply is sufficient)
Automatic changeover of resolution
RH  < 7 kΩ
Resolution  0.01 Ω
RH  < 50 kΩ
Resolution  0.1 Ω
RH  > 50 kΩ
Resolution  1 Ω
Interference voltage display dc + ac
Vmax  30 Veff
Common mode rejection  > 80 dB at 50 Hz and 60 Hz
Ri  680 kΩ
Measuring uncertainty  < 10 % for pure ac and dc signals

Earth Ground loop resistance measurements for commercial, industrial, and utility applications

The clamp-on ground testing technique used by the Fluke 1630 simplifies ground loop testing and enables non-intrusive leakage current measurement. The compact and rugged design makes the Fluke 1630 easy to use in small places and harsh environments, while the ‘display hold’ and the continuity testing with an audible alarm function ensures convenience in use. The novel technique means that earth ground loop testing and continuity testing can be completed without breaking the circuit.

Stakeless testing system
The Fluke 1630 uses the Stakeless testing method, which eliminates the need to disconnect parallel ground rods and find suitable locations for placing auxiliary ground stakes. This saves time and enables users such as industrial and utility electricians, and field service electricians and contractors, to perform earth ground loop tests in locations where it is not possible to use other techniques, including inside buildings or on power pylons. With the Stakeless testing method, earth ground stakes are no longer necessary. The Fluke 1630 Earth Ground Clamp is placed around the earth ground rod or the connecting cable. A known voltage is induced by one half of the clamp and the current is measured by the other half. The tester automatically determines the ground loop resistance at this grounding connection. For stakeless testing at least two ground rods (or ground connections of the ground system under test to earth) are required to close the loop the test voltage is induced.

  • A wide ground loop resistance range, from 0.025 Ω to1500 Ω, to satisfy all requirements
  • Large jaw opening of 35 mm (1.38 in) for tests on ground conductors and/or equipotential bus bars
  • Measurement of ground leakage current, from 0.2 mA to 1000 mA, without needing to disconnect – ideal for system troubleshooting
  • Wide ac current measurement range from 0.2 A to 30 A allows one instrument for multiple applications
  • User-defined HI / LO Alarm limits, for rapid measurement evaluation
  • Handy ‘display hold’ button for capturing readings in hard-to-reach places
  • Time saving memory function automatically records and stores measured values
  • Automatic self calibration ensures correct measurement every time
  • Overload protection: 200 A
  • Carrying case and resistance test loop included
  • ≥ 8 hours battery life (continuous operation)

Test the grounding components of equipment in hard-to-reach spaces, including areas that are indoors or fully paved and do not permit driving auxiliary test stakes. Stay on line—identify ground loop resistance without the need to disconnect then reconnect the earth electrode from the system.

The Fluke 1630-2 FC Stakeless Earth Ground Clamp is the kind of high-quality, rugged tool you expect from Fluke. Heavy-duty clamp jaw stays in alignment and in calibration even in every day, on-the-job industrial environments.

Earth ground ac leakage current measurement

Identify ac leakage currents without disconnecting the earth ground stake from the grounding system–ideal for system troubleshooting.


Heavy-duty clamp jaw stays in alignment and in calibration even in every day, on-the-job industrial environments.

Logging measurements

The earth ground clamp saves time by automatically recording data at pre-set intervals and saves up to 32,760 measurements in memory at the set logging interval. Saves time by recording and storing measured values.

Alarm threshold

User-defined high/low alarm limits, for rapid measurement evaluation.

Band-pass filter

Selectable band-pass filter function removes unwanted noise from the ac leakage current measurement.

Maximum voltage to earth ground 1000 V
Battery type AA alkaline IEC/EN LR6 (x4)
Battery life More than 15 hours*
* In Ground Resistance measurement mode, with backlight turned off, and RF mode turned off
Frequency range 40 Hz to 1 kHz
Ingress protection IEC/EN 60529: IP30 with jaw closed
LCD Digital reading 9999 counts
Refresh rate 4 per second
Operating temperature -10 °C to + 50 °C
Storage temperature -20 °C to + 60 °C
Operating humidity Non condensing (<10 °C) (< 50 °F)
≤90% RH (at 10 °C to 30 °C [50 °F to 86 °F])
≤75% RH (at 30 °C to 40 °C [86 °F to 104 °F])
≤45% RH (at 40 °C to 50 °C [104 °F to 122 °F])
(Non condensing)
Operating altitude 2000 m (6561 feet)
Storage altitude 12 000 m (39,370 feet)
Reference temperature 23 °C ±5 °C (73 °F ±9 °F)
Temperature coefficient 0.15% x (specified accuracy)/ °C (<18 °C or >28 °C [<64.4 °F or >82.4 °F])
Overload indication OL
Data logging capacity Minimum of 32,760 measurements
Data logging interval 1 second to 59 minutes and 59 seconds
Display reading specification with standard loop resistance
Input (Ω) Minimum Maximum
0.474 0.417 0.531
0.5 0.443 0.558
10 9.55 10.45
100 96 104
General IEC/EN 61010-1: Pollution Degree 2 IEC/EN 61557-1
Measurement IEC/EN 61010-2-032: CAT IV 600 V / CAT III 1000 V
Current clamp for leakage current measurements IEC/EN 61557-13: Class 2, ≤30 A/m
Resistance to earth IEC/EN 61557-5
Effectiveness of thepProtective measures IEC/EN 61557-16
Electromagnetic compatibility (EMC) International IEC/EN 61326-1: Portable Electromagnetic Environment
CISPR 11: Group 1, Class B, IEC/EN 61326-2-2
Korea (KCC) Class A equipment (Industrial Broadcast & Communications Equipment)
USA (FCC) 47 CFR 15 subpart B. This product is considered an exempt device per clause 15.103
Wireless Radio
Frequency range 2412 MHz to 2462 MHz
Output power <10 mW
Radio frequency certification FCC ID:T68-FBLE IC:6627A-FBLE
General Specifications
Conductor size 40 mm (1.57 in) approximately
Dimensions (L x W x H) 283 x 105 x 48 mm (11.1 x 4.1 x 1.9 in)
Weight 880g (31 oz)
Warranty One year
Earth Ground Loop Resistance
Range Accuracy1  ± (% of reading + Ω)
0.025 Ω to 0.249 Ω 1.5% + 0.02 Ω
0.250 Ω to 0.999 Ω 1.5% + 0.05 Ω
1.000 Ω to 9.999 Ω 1.5% + 0.10 Ω
10.00 Ω to 49.99 Ω 1.5% + 0.30 Ω
50.00 Ω to 99.99 Ω 1.5% + 0.50 Ω
100.0 Ω to 199.9 Ω 3.0% + 1.0 Ω
200.0 Ω to 399.9 Ω 5.0% + 5.0 Ω
400 Ω to 599 Ω 10.0% + 10 Ω
600 Ω to 1500 Ω 20.00%
1  Loop resistance with no inductance, conductor centered and perpendicular to jaw
Earth ground leakage current mA
Autorange 50/60 Hz, True rms, crest factor CF ≤3
Range Resolution Accuracy1  ± (% of reading + mA)
0.200 mA to 3.999 mA 1 μA 2.0% + 0.05 mA
4.00 mA to 39.99 mA 10 μA 2.0% + 0.03 mA
40.0 mA to 399.9 mA 100 μA 2.0% + 0.3 mA
0.400 A to 3.999 A 1 mA 2.0% + 3 mA
4.00 A to 39.99 A 10 mA 2.0% + 30 mA
1 Applies to signal frequency

  • 40 Hz to 1 kHz with filter set to OFF
  • 40 Hz to 70 Hz with filter se to ON

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