The EM-4056 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.

It is also suitable for soil resistivity measurements, in order to optimise the earth systems project. It is a fully automatic and easy-to-operate equipment. Before starting each measurement, the equipment will check that conditions are within appropriate limits and will notify the operator in case any abnormality turns up (too high interference voltage, too much resistance in test spikes, very low test current, etc). Then, it will look for the most suitable range and show measurement results in an alphanumeric display.

In order to conveniently test the earth system, EM-4056 allows to perform measurements using the test current which frequency may be operator-selected (270 Hz, 570Hz, 870Hz, 1,170Hz or 1,470 Hz). On one hand, the lowest frequency will allow to analyse the earth system behaviour related to fault currents of industrial frequency, while on the other hand, the measurement performed with the highest frequency will best show the behaviour 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 EM-4056 has a Frequency Scan feature that performs an earth resistance measure with all available frequencies automatically and calculates, display and print the avarage result besides the individual result of each frequency. Those results are saved on the internal memory. 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.

The EM-4056 has a built-in memory to store measurements and a built-in printer (optional), besides the USB interface that allows to communicate measured values to a computer or data logger for their later analysis. It is a portable, strong and lightweight equipment, suitable to be used out in the field and under severe weather conditions. It is powered by a rechargeable battery with a 110 V or 220 V charger and it is supplied with all the necessary accessories for measurements (test spikes, leads, etc) within an auxiliary case that makes it simple to carry.