On offer today we have something that is exotic, historical and scarce - it is of course a Fleming-Gimingham dynanometer voltmeter. This beautifully made meter was crafted by two brilliant minds, first, Fleming was a consultant for the Edison-Swan company and Gimingham their Works Manager.
They designed and released their meter in J Telegraph Eng. 24th Nov 1887 which consisted of two moving coils mounted at the end of an ivory or ivorine beam supported by an inverted steel cup with an indium tipped post. When the lid was screwed down, a rod and lever tilted the coils on a pair of cloth lined cradles against the fixed coils. The balance pointer is viewed through an aperture in the centre of the nickel plated top plate and it is essential that the meter is levelled prior to use. The mica scale pointer is rotated until the balance index meets zero, the knob is then loosened, scale pointer reset to zero and tightened. When energised, the moving coil assembly rotates and balance is restored by dial rotation upon which the null point indicates the measured voltage.
A scarce and beautiful historical instrument indeed.