A Simple Lead Indicator

Radio Record, Volume III, Issue 45, 23 May 1930, Page 28

A Simple Lead Indicator

[= is often necessary to find ont which is which of various battery leads, particularly when multiple cables and twin-flex wire is employed. If you have a voltmeter of the polarised type, that is to say, one which has to be connected a certain way round as regards positive and negative, this is a simple matter. All you need do is to connect the voltmeter at the end of the leads from a battery and note whether a reading is obtained or whether the needle tries to -kick back off the scale. If the needle indicates a° reading, the positive lead is the one joined to the positive terminal of the meter; or if the needle kicks back, then the positive lead is the one joined to the negative terminal. The meter must not be used on voltages greater than the maximum reading on its scale. It will be appreciated that this method of telling one lead from an-

other is very useful in the case of! loud-speaker and other extension leads. In this case, a small battery should be connected across two of the wires at’ one end, and the meter joined across) various pairs of. wires (if there are) more than two leads) at the other end. . When the meter is connected to thie, same two as the battery, the needle’ will move, and according to whether } it kicks back or gives a proper read-| ing it will be possible to tell which of} the two wires is joined to the positive, of the battery. The meter is thus be-' ing used as a polarity indicator ‘apd: enables you to differentiate between } the various leads. Me '