The ER25 earth tester is a digital, micro-processor controlled instrument that measures the earth resistance and ground resistivity (using Wenner´s method), as well as detect parasitic voltages present in the ground. This instrument is suitable to measure earth systems in power substations, distribution networks, and other industries, according to IEC 61557-5.

It is also suitable for soil resistivity measurements, in order to optimize an earth system project. Before starting each measurement, the equipment will check that conditions are within appropriate limits and will notify the operator of any abnormality (too high interference voltage, too much resistance in test spikes, very low test current). Then, it will look for the most suitable range and show measurement results in an alphanumeric display.

The ER25 performs measurements using the test current with an operator selected frequency (270 Hz or 1470 Hz). The lower frequency will analyze the earth system behavior related to fault currents of industrial frequency. A measurement performed with the higher frequency will show the behavior in connection with electrical currents caused by lightning and provide a very high immunity related to interference voltages that are usually present in soil, especially near substations.

The instrument has four ranges that are automatically selected, covering measurements from 0.01Ω up to 20kΩ, which allows to obtain very accurate measurements for any kind of soil. 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.

Testing Applications

Perform earth resistance measurements of simple or complex electrode systems, ground resistivity measurements (4-wire Wenner´s principle), and spurious voltage measurements according to IEC 61557-5.

The equipment injects an electronically generated current in the soil. Both current and voltage developed are measured with high precision.