11 July 2009

Electrical Testing Method

From The Electrician's Handbook, 1928: 


Electricians often test circuits for the presence of voltage by touching the conductors with the fingers. This method is safe where voltage does not exceed 250 and is often very convenient for locating a blown-out fuse or for ascertaining whether or not a circuit is alive. Some men can endure the electric shock that results without discomfort whereas others cannot. Therefore, the method is not feasible in some cases. Which are the outside wires and which is the neutral wire of a 110-220 volt, 3-wire system can be determined in this way by noting the intensity of the shock that results by touching different pairs of wires with the fingers. Use the method with caution wan be certain that the voltage of the circuit does not exceed 250 before touching the conductors

The presence of low voltages can be determined by "tasting". The method is feasible only where the pressure is but a few volts and hence is usde only in bell and signal work. Where the voltage is very low, the bared ends of the conductors are held a short distance apart on the tongue. if voltage is present a peculiar mildly burning sensation results which sill never be forgotten after one has experienced it. The "taste" is due to the electrolytic decomposition of the liquids on the tongue...


Mark Miller said...

The tongue-touch method works particularly well for seeing whether that old 9 volt battery at the bottom of the drawer is good or not. Try it sometime. It's just tingly, it doesn't burn.

120 volt power from wall plugs delivers a pretty good jolt. Everybody who works around electricity has been "bitten" by it accidentally. It's just a little too intense to want to do it on purpose. But yes, it can be done safely.

dave said...

That is very shocking information.