Finding the true live wire

Problem: Those engaged doing electrical work at home or commercially are concerned to avoid touching live wires. Products to detect live wires abound. The most common is the screwdriver with a neon lamp. Next most common are non contact devices picking up electric fields emitted by cables. Both suffer from the fact that if neutral and earth wires are disconnected from a path to earth, and the live wire is still live, either test method will show all three cables as live, because of induced voltages. In some cases the induced voltages will be as little as 5V below true live, making it most difficult to distinguish true live wires. Solution: Kew Technik has developed an Easy Phase Finder that can establish which cable is truly live. The EPF 30 uses a built-in microprocessor to perform a scan. As the probe is brought into contact with each of the conductors in turn, the voltages are detected and recorded, and when the cables are scanned again, highest voltage, taken to be true live, is indicated by a red LED and a continuous audible tone. The ability to differentiate true live from other conductors is invaluable when it comes to detecting faults such as reversed line and neutral in a 230V switched outlet fault. The fault is potentially dangerous to the user, as turning off a conventional single pole switch would not isolate an appliance plugged into the socket. Applications: The testers are suitable for use on 110-130V, 200-230V and 380-415V supplies. Selling price is "Under £30." The same principle of scanning and then coming to a decision based on the strongest signal can be applied to wide range of test equipment. TS Kew Technik