Video: AMRU-10

Video transcript

The AMRU-10, a handheld earth resistance meter with three terminals and two methods. How it is set up, how it is connected, and how to know the result can be trusted. An earth electrode protects people only while its resistance stays low, and soil and connections change over the years. The routine check of an electrode needs a meter that is quick to carry, simple to use, and accurate even with interference on the earthing. resistance by the three-pole method from 0.53 ohms to 9,999 ohms to EN 61557-5. A quicker two-pole method.

The probe resistance is up to 19.9 kilombs. An interference voltage up to 100 volts. The large backlit display shows the result and the active terminals. START runs the measurement. The down key switches between two-pole and three-pole. The up key steps through the partial results. And the bottom key switches on the meter and the backlight. Three terminals on the top edge.

E, black, for the electrode under test. S, red, for the voltage probe. And H, yellow, for the current probe. The inputs withstand up to 276 volts for 30 seconds if they touch a live circuit by mistake. Settings are made once. Switch on while holding the down key. Then set the mains frequency, 50 or 60 hertz. The beeper, the automatic switch off, and the test voltage, 25 or 50 volts.

A long press on start saves them. the three-pole method, the meter drives a current from E through the soil to the current probe H. The voltage probe S picks up the voltage drop across the electrode. Ohm's law gives the earth resistance. The test signal runs at 125 hertz, away from the mains frequency. Disconnect the electrode from the installation first, so that it is measured on its own.

E goes to the electrode, S to the voltage probe, and H to the current probe, the furthest away. Electrode and probes stand in one line. Then press start. The earth resistance appears at the bottom of the display, with the current probe resistance above it. The up key steps through the voltage probe resistance, the extra uncertainty caused by the probes, and the interference voltage.

A flashing E, S, or H means a lead is not connected, or that probe is out of range. Then check the result. Move the voltage probe a few meters closer to the electrode and further away. If the readings differ by more than 3%, move the current probe much further out and repeat. Poor probe contact adds uncertainty, water the ground, or use a longer probe. Before every test, the meter measures the voltage already present between the terminals.

Up to 24 volts it measures, with a noise warning if the interference is high. Above 24 volts the test is blocked, above 40 volts it beeps, and it must never be connected to more than 100 volts. the earthing system is known and an earth of known resistance is at hand, the two-pole method is quicker. E goes to the main earthing terminal, and S to the socket outlet that leads to the known earth. The result is the sum of both earth resistances.

set includes test leads of 30 and 15 meters on reels, a 2.2-meter lead with a crocodile clip, two 25-centimeter earth probes, batteries, and a carrying case. 80-centimeter probes and longer leads are options. An IP67 housing, measuring category 4 at 150 volts, about 660 grams, and four AA batteries good for more than 3,000 three-pole measurements. Earth electrodes of buildings and installations, substations and lightning protection,

periodic inspections by installers and maintenance teams. Earth resistance testing, from Amperis.