Digital earth tester

January 2014 Electrical Power & Protection

The Megger DET3TD digital earth tester is a compact instrument designed to measure earth electrode resistance. It uses the three-terminal method of measurement where the resistance of the current circuit does not affect the reading. The resistance of the potential circuit does not affect the measurement either. Pressing a latchable button allows for one finger testing in either the two- or three-wire mode. The reversing AC test current has a frequency of 128 Hz, which avoids possible interference from other 50 and 60 Hz stray currents in the vicinity of the earth electrode under test. In the interests of safety, the maximum test voltage has been limited to 50 V. The DET3TD automatically checks that both current and voltage probes are ready for testing before the test commences.

There are two measuring ranges selected by a rotary switch that allows for two- or three-pole testing. The instrument is simple to use and there is no test button to hold down. The readings are displayed quickly, directly and accurately on the 3½ digit LCD.

Annunciators on the display indicate if the noise interference in the soil passing the test current is excessive, or if the current test spike resistance or potential test spike resistance is too high. The direct indication of these factors speeds the testing procedure and gives assurance of valid measurements. The low service error and wide operating temperature range enable accurate results to be achieved in on-site conditions. Powered by eight penlight batteries, the DET3TD allows easy replacement of batteries in the field if required and it is supplied with a factory calibration certificate.

For more information contact Stuart Ashton, Surgetek, +27 (0)11 792 1303, [email protected], www.surgetek.co.za

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