Fluke 1625-2 GEO Earth Ground Tester with AFC

The Fluke 1625-2 GEO Earth Ground Tester is a professional instrument for testing earth grounding systems in electrical installations, substations, utility infrastructure and industrial facilities.

Unlike basic earth ground testers, the Fluke 1625-2 supports four major grounding test methods, allowing technicians to select the appropriate measurement technique according to the grounding system and site conditions. It can perform testing with auxiliary stakes, with clamps and with a combination of clamps and stakes.

Key Features

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  3- and 4-pole fall-of-potential earth ground testing
  
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  4-pole soil resistivity measurement
  
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  Selective ground rod testing using one clamp and auxiliary stakes
  
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  Stakeless ground loop testing using two current clamps
  
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  Automatic Frequency Control (AFC) for minimizing electrical interference
  
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  Up to 120 dB noise rejection
  
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  Earth resistance measurement from 0.020 Ω to 300 kΩ
  
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  Stakeless ground loop resistance measurement from 0.02 Ω to 199.9 Ω
  
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  Interference voltage measurement from 1 V to 50 V
  
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  Interference frequency measurement from 6 Hz to 400 Hz
  
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  USB port for data storage and transfer
  
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  Internal memory for up to 1,500 records
  
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  IP56 protection for outdoor use
  
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  Adjustable measurement limits
  
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  Rugged carrying case included
  

Four Earth Ground Testing Methods

The Fluke 1625-2 supports multiple grounding measurement methods in one instrument.

3- and 4-Pole Fall-of-Potential Testing

The traditional fall-of-potential method uses auxiliary ground stakes to measure earth resistance. The 4-pole configuration can also be used for soil resistivity testing.

Selective Ground Rod Testing

Selective testing combines an auxiliary ground probe with a current clamp, allowing the resistance of an individual grounding electrode to be evaluated without disconnecting the complete grounding system.

Stakeless Ground Loop Testing

The two-clamp stakeless method measures ground loop resistance without auxiliary ground stakes. This can be particularly useful on multi-grounded systems where disconnecting parallel grounds would be time-consuming or unsafe.

Automatic Frequency Control

The integrated Automatic Frequency Control (AFC) helps reduce the influence of electrical interference during earth ground measurements.

The Fluke 1625-2 can select appropriate test frequencies, with the earth resistance function using manually selected or automatically controlled frequencies. The instrument also provides up to 120 dB noise rejection for common interference frequencies.

Earth Resistance Measurement

The Fluke 1625-2 measures earthing resistance over a broad range:

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  Measurement range: 0.020 Ω to 300 kΩ
  
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  Resolution: down to 0.001 Ω
  
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  Basic accuracy: ±(2% of reading + 2 digits)
  
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  Operating error: ±(5% of reading + 5 digits)
  
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  Typical measurement time: approximately 8 seconds with a fixed frequency
  
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  AFC measurement cycle: up to approximately 30 seconds depending on test conditions
  

Stakeless Ground Loop Measurement

For closed-loop grounding systems, the Fluke 1625-2 provides two-clamp stakeless measurement:

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  Measurement range: 0.02 Ω to 199.9 Ω
  
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  Accuracy: ±(7% of reading + 3 digits)
  
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  Operating error: ±(10% of reading + 5 digits)
  
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  Measurement frequency: 128 Hz
  
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  Maximum external interference current: up to 10 A AC for low-resistance loops under specified conditions
  

Soil Resistivity Testing

The 4-pole method allows the Fluke 1625-2 to perform soil resistivity measurements, which are useful when evaluating grounding conditions before designing or modifying an earth electrode system.

Interference Voltage and Frequency

The instrument can also identify electrical interference that may affect grounding measurements.

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  Interference voltage: 1–50 V
  
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  Voltage resolution: 0.1 V
  
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  Interference frequency: 6–400 Hz
  
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  Frequency resolution: 0.1 Hz to 1 Hz
  
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  Frequency accuracy: ±(1% of reading + 2 digits)
  

Data Storage and USB Transfer

The Fluke 1625-2 includes internal memory capable of storing up to 1,500 measurement records. A built-in USB interface allows measurement data to be stored and transferred for further documentation and analysis.

Outdoor and Field Applications

With an IP56-rated case, the Fluke 1625-2 is designed for demanding field environments.

Typical applications include:

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  Electrical substation grounding testing
  
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  Utility grounding system inspection
  
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  Power distribution systems
  
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  Industrial grounding systems
  
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  Ground rod testing
  
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  Ground grid testing
  
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  Soil resistivity surveys
  
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  Lightning protection grounding
  
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  Telecommunications grounding
  
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  Commercial building grounding
  
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  Renewable energy installations
  
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  Maintenance and verification of earth electrode systems
  

General Specifications

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  Display: 4-digit, 2999-count LCD
  
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  Earth resistance range: 0.020 Ω to 300 kΩ
  
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  Stakeless loop range: 0.02 Ω to 199.9 Ω
  
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  Interference voltage: 1–50 V
  
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  Interference frequency: 6–400 Hz
  
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  Operating temperature: -10 °C to 50 °C
  
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  Storage temperature: -30 °C to 60 °C
  
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  Protection rating: IP56 for case
  
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  Power: 6 × 1.5 V AA alkaline batteries
  
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  Typical battery life: approximately 3,000 to 6,000 measurements, depending on test conditions
  
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  Dimensions: 250 × 133 × 187 mm
  
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  Weight: approximately 1.1 kg without accessories
  

FAQ

What does the Fluke 1625-2 measure?

It measures earth resistance, ground loop resistance, interference voltage and interference frequency, and can perform soil resistivity testing.

Can the Fluke 1625-2 perform stakeless ground testing?

Yes. The two-clamp stakeless method measures ground loop resistance without requiring auxiliary ground stakes.

What is AFC on the Fluke 1625-2?

AFC stands for Automatic Frequency Control. It helps select appropriate test frequencies and reduce the influence of electrical interference during grounding measurements.

Can the Fluke 1625-2 test soil resistivity?

Yes. It supports 4-pole soil resistivity testing using the stake-based method.

How much measurement data can the Fluke 1625-2 store?

The internal memory can store up to 1,500 records, which can be transferred through the USB interface.

Is the Fluke 1625-2 suitable for outdoor testing?

Yes. The instrument case is rated IP56, making it suitable for outdoor field applications when used according to the manufacturer's operating conditions.