Measuring device

Abstract

A measuring device for measuring the value represented by an indication on a graph, chart, map, or the like, having a calibration scale. The measuring device can accommodate any calibration scale over a wide range. The measuring device includes a first member, having a first reference indication on it, and a second member, having a second reference indication on it. The second member is movable with respect to the first member between a closed position, in which the two reference indications are adjacent each other, and an extended position, in which the two reference indications are separated. A first voltage signal, indicative of the separation of the first and second members, is applied to a ratiometric digital voltmeter which also receives as an input a second voltage signal determined by the setting of a manually adjustable control. The ratiometric digital voltmeter provides an output signal that is indicative of the ratio of its two input voltages, and this output is indicated on a digital display unit. In use, the two reference indications are placed at the two ends of the calibration scale indication of the graph, chart, map, or other such paper, to apply to the ratiometric digital voltmeter a first voltage signal indicative of that calibration scale indication, and the manually adjustable control is adjusted until the calibration value represented by that calibration scale indication is shown on the digital display unit. The two reference indications are then placed at the two ends of the indication to be measured, and the ratiometric voltmeter output, shown on the digital display unit, then represents that measured value.

Dependencies are inferred from the claim text.