In the days when having a valve "wireless" meant periodically puchasing an expensive High Tension battery of maybe 90 or 120 Volts and regularly taking your 2 Volt lead acid accumulator to the local radio shop or garage for recharging, it was necessary for the owner to have a means of establishing if the poor performance of the radio was due to "flat" battery or something more serious. These examples are typical of many which were available in the 1920's and 1930's. All these instruments are of the moving iron type.
Battery testing Pocket Meter chrome case with cardboard box DC 0-12V 0-120V working foreign
Battery testing Pocket Meter chrome case in imitation leatherette covered wooden box DC 0-12V 0-120V working foreign
I believe that this is a later instrument probably dating from the
Voltmeter Pocket DC 0-25V 0-250V not working
This little meter given to me by Brian Webster who inherited it from
his father. It doesn't work, the meter coil is open circuit (the larger
of the two in the picture below). I am puzzled as to why it has a red
mark at 18/180 volts and that it is labelled as “voltmeter pocket”
which makes it sound rather military though there is no broad arrow.
During the war his father was employed as an aircraft fitter in the
Midlands and his guess is that he used it when working on Spitfires.
Interior showing the shaped moving iron
vane attached to the aluminium pointer. The larger coil provideds the
magnetic field and the smaller ia a dropper resistance used on the
higher voltage range. The plastic sleeving on the interior connections
was not commonly used until WW2.