ABSTRACT
For measurements o f the relative-angular-positional-error 8 in the mul t i - reading-head method and the relative measurement o f the test scale referred to the master scale, a time-conversion method is used to detect slight angular differences automatically wi th high resolution. The basic principle o f the time-conversion method is based on measuring the time intervals between pulses o f the master scale and the test scale when they are rotating at a constant speed. Seven counter circuits are provided that can measure simultaneously the time intervals be-
tween the pulses from the reading head H I and other heads ( H ,...,H6 and so on) as
shown in Figure 12. The counter counts the clock pulses o f the crystal oscillator
and the counted values are transmitted to the microcomputer. Since the clock used
a frequency o f 8 M H z , the angular resolution becomes 0.0135 in. at 5 rpm.
