FINISH MEASURING METHOD AND APPARATUS

摘要

FINISH MEASURING METHOD AND APPARATUS The amount of electrically conductive finish that has been applied to a filament is determined by measuring the conductance of a length of the filament. The measurements are made independently of any differences in conductivity of finish mediums by means of a reference cell containing a sample of the particular finish medium used. An electric measurement circuit provides an indication of the amount of finish medium on the filament by determining the ratio of the conductance of the length of filament to the conductance of the reference cell. In one circuit embodiment, two operational amplifiers are placed in series. The reference cell takes the place of the feedback resistor of one operational amplifier and the length of filament takes the place of the input resistance of the other amplifier. The resulting output of the series circuit is a scaled ratio of the conductances of the finish along the length of filament and in the cell. In another circuit embodiment, voltages applied through the length of filament and reference cell are selectively switched into a dual slope integrating circuit. In its preferred form, the finish measuring apparatus is a hand-held device having contacts which may be connected to a filament using a trigger mechanism.