Video: AMRU-200

Video transcript

The AMRU-200 brings every earth test into one meter, including the impulse method for lightning protection, what it measures, and how it is connected for each method. A substation, a tower line, and a lightning protection system each need a different earth test, probes where the ground allows, clamps where the earth cannot be disconnected, and an impulse that behaves like lightning where the earth has to drain a strike. and four pole earth resistance from 0.1 ohm to nearly 20 kilo ohms.

Methods with one and with two clamps. Impulse impedance up to 300 ohms with three standard waveforms. And soil resistivity, plus leakage current with a clamp. The terminals are along the top edge, the clamp socket, then E, ES, S, and H, each in its own color. The rotary switch selects the method from two-pole to impulse, resistivity, current, and memory. The F keys set the test voltage, the clamp,

or the pulse shape, and start runs the test. The hard case carries everything for a three- or four-pole test. For earth probes, leads on reels of 25 and 50 meters, shorter leads and clips. The battery is charged from the mains adapter or from a car socket. Clamps and the flexible clamp adapter are options. Every test follows the same routine. Turn the switch to the method. Use F1 to set the test voltage or the pulse shape.

Connect. Press start. Read the result with the probe resistances and press enter to store it. The basic test is three-pole. Disconnect the electrode from the installation. E goes to the electrode, S to the voltage probe, and H to the current probe, the furthest away, all in one line. Then move S a few meters both ways. The readings should agree within 3%.

With a multiple earth, the test link can stay closed. Connect E, S, and H as before, then put the measuring clamp on the electrode below the E connection. The clamp sees only the current in this electrode, so only its resistance is measured. Where no probe can be driven, two clamps do the job. The transmitting clamp connects to H and E, the measuring clamp to the clamp socket, both round the electrode at least 30 centimeters apart.

This works only on multiple earths. A lightning current rises in microseconds. At that speed, the inductance of the earth conductors matters, so a long, low-resistance earth can show a much higher impedance to a strike. The impulse method sends pulses shaped like lightning and divides the peak voltage by the peak current. Turn the switch to four-pole impulse. E goes to the downconductor, and the shield of the H lead joins E.

E-S goes on the same conductor below the E lead. S and H go to their probes, with the leads fully unrolled and at least 60 degrees apart. The test joint stays closed. Bonding and protective conductors are tested with two leads and at least 200 milliamps. Zero the leads first with F1. Then E goes to the main earthing terminal, and S to the bonded metalwork.

Before every test, the meter measures the interference voltage and its frequency. It filters 16 and two-thirds, 50, 60, and 400 hertz networks, chosen automatically. Above 24 volts, the test is blocked. And on the current position, a clamp measures leakage currents from a tenth of a milliamp to 300 amps. Results go into 990 memory cells in 10 banks, each with date and time. They are sent to a computer over USB or Bluetooth, or to a mobile phone app, for the measurement report.

Measuring Category 4 at 300 volts, an IP54 case, about 2 kilos, and a nickel metal hydride pack that charges in about 4 hours. Substations and power plants, tower lines without disconnecting the earth, lightning protection systems tested by impulse, bonding checks, and soil surveys before a new earthing design. Earth resistance testing, from Amperis.