Electronic caliper using a self-contained, low power inductive position

Abstract

An electronic caliper using a low power induced current position transducer includes a slider assembly mounted on an elongated beam with first and second measuring jaws projecting from the main beam and slider assembly. The position of the slider assembly on the beam is indicative of the distance between the first and second jaws. A depth bar is also attached to, and projects from, the slider assembly. Relative movement between the measuring jaws is determined by an inductive read head mounted on the slider assembly that couples to flux modulators on the beam. The read head includes a transmitter winding and a pair of receiver windings carried by a common printed circuit board. The flux modulators, which can include both flux disrupters and flux enhancers, are carried by the beam and modulate the magnetic fields produced by the transmitter. Thus, the receiver windings produce output voltages corresponding to the overlap between the modulators and the receiver windings. Signal processing electronics are connected to the read head and determine the relative positions of the jaws by monitoring the output of the receiver windings. A digital display displays the determined position. In one embodiment, either flux enhancers or flux disrupters are used. In another embodiment, both flux disrupters and flux enhancers are used. The relatively insensitive nature of the low power induced current position transducer to industrial contaminants allows the caliper to function with improved reliability when operating in traditional shop environments.