In the new Australian Standard AS 4741 there is a very specific and strict requirement to accurately measure the supply loop impedance (on the supply side) of an Electrical Utility's electricity supply to the customer. The spec states the the impedance of the active and neutral cables running to a residential or commercial premises shall not exceed 1 Ohm. Other meters of this type on the market are not accurate enough in the 0 - 1 Ohm scale so we were approached to develop such a device. We set about researching the formula to calculate the supply loop impedance, developed a 16 bit 2 channel synchronous sampling ADC Interface to take simultaneous voltage and current measurements and developed an aluminium clad power resistor & 1200V 35A IGBT loading circuit. The result was the Supply Loop Impedance Meter (SLIM) that accurately measures and displays the supply loop impedance to an accuracy of +/- 0.01 Ohms in the 0 - 2 Ohm scale using the in-built 20 Amp loading circuit.

SLIM is currently on trial with Ergon Energy.