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EM 4058

EM 4058

The EM-4058 earth tester is a digital, microprocessor controlled instrument that allows to measure the earth resistance and ground resistivity (using Wenner´s method), as well as to detect parasitic voltages present in the ground. This instrument is suitable to measure earth systems in power substations, industries, distribution networks, etc., according to IEC 61557-5.

In order to conveniently test the earth system, EM4058 allows to perform measurements using the test current which frequency may be operator-selected (270 Hz, 570 Hz, 870 Hz, 1170 Hz or 1470 Hz). On one hand, the lowest frequency will allow to analyze the earth system behavior related to fault currents of industrial frequency, while on the other hand, the measurement performed with the highest frequency will best show the behavior in connection with electrical currents caused by lightning and will offer a very high immunity related to interference voltages that are usually present in soils, specially near substations.

The instrument has four ranges that are automatically selected, covering measurements from 0.01 Ω up to 20 kΩ, which allows to obtain very accurate measurements for any kind of soils. During ground resistivity measurement, the operator may indicate the distance between spikes in order for the equipment to apply Wenner's formula and to show the resistivity value directly.


  • Earth resistance measurement
  • Ground resistivity (Wenner's method)
  • High spurious voltage rejection
  • Spurious voltage measurement
  • Measure with multiples frequencies (270 Hz, 570 Hz, 870 Hz, 1170 Hz, 1470 Hz)
  • 0.01 Ω resolution
  • Up to 20 kΩ resistance range
  • Remote control through an Android App
  • Auto-range
  • Built-in memory
  • Built-in printer
  • USB interface


Measurement ranges

Resistances: 0-20 Ω; 0-200 Ω; 0-2,000 Ω; 0-20 kΩ (Auto-ranging)

Resistivity :  0- 50 kΩm (auto ranging)

Voltage: 0-60 V~


Resistance & Resistivity measurements:

R ≤ 2 kΩ: ± (2% of the measured value ± 2 digits).
R > 2 kΩ: ± (5% of the measured value ± 2 digits).

Voltage measurements:

± (2% of the measured value + 1% of end of scale value).

Reading resolution

0.01 Ω in the resistance measurement;

0.01 Ωm in the resistivity measurement;

0.1 V in the voltage measurement.

Output Current The short-circuit current is limited to less than 20.0 mARMS (according the IEC 61557-5 - 4.5).
Operation Frequency

270 Hz (resistance or resistivity measurement)

570 Hz, 870 Hz, 1170 Hz or 1470 Hz (resistance measurement)

Max. variation: ± 1 Hz (both cases).

Battery charger A smart, microprocessor controlled, circuit adjusts the battery charge to the optimised parameters in order to ensure the maximum service life. It is supplied by means of an external AC adapter (provided with the equipment) or from a 12 V car battery.
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