Direct readout distance measuring device

Claim 1

Apparatus for measuring the distance between a datum point and one or more further points comprising an elongate member; a cursor attached to said elongate member so as to slide along said elongate member, the position of said cursor providing an indication of the distance between the point at where said cursor is positioned and said datum point, a resistor, having two end terminals, affixed to said elongate member and extending along the length of said elongate member, said resisor being calibrated to have an uniform resistance per unit length between the end terminals thereof, a constant voltage supply connected to the two end terminals of said resistor, said cursor having an electrical contact for contacting said resistor at a point so as to form a potentiometer with said resistor and said supply, the output of said potentiometer varying directly with the position of said cursor, and voltage detector means connected to the output of potentiometer to provide an indication representative of the distance between said datum point and the position of said cursor, said detector means comprising a digital voltmeter providing a digital readout, said voltmeter being connected to the output of said potentiometer and providing a high impedance relative to that of said resistor.