# Power detection technology / Power detection

## Detection Technology

### Earth resistance tester measures resistivity

The most sophisticated earth resistance tester also provides a measurement of earth resistivity, defined as a cube with a soil/ground resistance of 1 x 1 x 1 meter (1 cubic meter).

Ground resistivity measurements can be used in soil surveys to establish optimum design, depth, and site location for ground electrode systems. For example, when new power stations, substations, transmission towers, telecommunications stations or towers are under construction, such surveys are carried out. If there is no such investigation, additional costs for reinstallation of the electrode device may be required at the end of the construction.

Ground resistivity measurements can be used to indicate the expected corrosion of underground pipelines to water, oil, natural gas, gasoline, etc. In general, corrosion tends to increase in areas with low resistivity values. This information is a good guide for installing cathodic protection devices in underground metal piping.

Finally, earth resistivity measurements can be easily used in geophysical research.

For example, minerals, clays and water-bearing gravel are located below the surface to determine the depth of bedrock and the thickness of glacier drift.

Principle of ground resistivity measurement

The earth resistance tester for measuring earth resistance has four terminals and four auxiliary earth electrodes.

According to Wenner 4-pole method, alternating current "I" was applied between "E" (ground electrode) and "H (C)" (current electrode) to find the potential difference "V" between the two potential electrodes. S (P) "and" ES ". To get the grounding resistance "Rg" (Ω), please send electric potential difference "V" divided by alternating current "I"; The distance between the electrodes is "A" (m). Then use the formula: rho = 2 PI xax Rg Ω (m).

For connections, all four auxiliary grounding electrodes shall be inserted into the ground at the same distance [m]. Note: Depth should be 5% or less of A.

For advanced resistivity testers using the above formula, the value of rHO is automatically calculated and displayed on the instrument's display.

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