British Army Blasting Galvanometer

In today’s world of disposable cheap electronics, it is often easy to forget that at one time electrical devices were well made and had a certain character. Tonight we are considering a wonderful little instrument; a galvanometer used to measure the minute electrical currents in a demolitions circuit:imageGalvanometers developed from the observation that the needle of a magnetic compass is deflected near a wire that has electric current flowing through it, first described by Hans Oersted in 1820. They were the first instruments used to detect and measure small amounts of electric currents. The name comes from the Italian electricity researcher Luigi Galvani, who in 1791 discovered the principle of the frog galvanoscope – that electric current would make the legs of a dead frog jerk. Sensitive galvanometers have been essential for the development of science and technology in many fields. For example they enabled long range communication through submarine cables, such as the earliest Transatlantic telegraph cables, and were essential to discovering the electrical activity of the heart and brain, by their fine measurements of current.

As can be seen, the main body of the instrument is in varnished wood, with brass screws holding everything together. The dial on the front of the instrument dates it to 1942 and has the /|\ mark:imageThe instrument is described as a ‘Detector Q&IATP’ with a stores code of ‘WA0275’. The instrument was manufactured by W.E.M. Co Ltd. Wemco was the trading name of ‘Walters Electrical Manufacturing Company who had factories at Kensaltown Works in the Kensal Road, London and in Whippendell Electric Works, Whippendell Road, Watford. The rear of the instrument has a printed plastic plate giving instructions on its use, and safety warnings:imageThe ‘I’ and ‘Q’ terminals referred to on this plate are mounted on the top of the instrument, with a large brass ring:imageThe back of the instrument is removable by loosening the screw at the base and sliding it off, inside the internal parts are again made with heavy duty brass:imageEverything about this instrument indicates the quality of its manufacture and it is as far from the throwaway objects of today as it is possible to be.

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