Commutator-Operated Digital Caliper with Visual Display and Card-Punch Capacity

Abstract

A variety of automatic and semiautomatic measuring devices with print-out, card-punch, and paper-tape capacity have been used in the analysis of lateral head radiographs, posteroanterior head radiographs, and oblique-jaw views. Such devices include the tape-printing GOAT ' the card punching GADRS-4 and GADRS5,T and the OSCAR.T These automatic measuring instruments have satisfactory readout accuracy down to 0.1 mm, are far faster than hand caliper measurements, and eliminate visual reading and transcription errors. However, the fixed X and Y coordinates render them relatively clumsy for measurements unrelated to a single reference line. Though dialreading calipers can be modified for electric digital display (S. M. GARN, R. H. HELMRICH, and A. B. LEWIS, J Dent Res 46:306, 1967), full card-punching capacity is not obtained without additional circuitry and components. As an alternative to the GADRS or OSCAR instruments, but using stock parts, use has been made of the Decitrak§ (Illustration). Essentially, this instrument consists of two functional parts: (1) the measuring-encoding unit, and (2) the digitizing output unit. Together they interface with an i13M 526 Printing Summary Punch, eliminate visual read-out error and transcription mistakes, obviate the need for precoding forms, and yield punch cards with a time saving of 90% over hand methods. The commutator-type encoding unit can be fitted with adjustable needle points for caliper micrometry, or with more conventional caliper