Commodity track movement monitor - includes incremental path sensor for applying correction for track speed to switching frequency of switched capacitor low=pass filter to be in fixed relationship of up to one half of A=D converter sampling frequency

摘要

A sensor (1) such as a differential field plate for detecting e.g. metal code markings on the moving track, or optical, capacitive inductive or ultrasound detectors, delivers an analog signal via an anti-aliasing filter (3) to a digitiser (2). The upper cut-off frequency of the filter is set by the frequency of switching (f0) of its capacitors by a converter (5) of the pulse repetition rate of an incremental detector (4) which establishes the sampling frequency (f1) for A/D conversion. The low-pass filter cuts off at a fixed fraction (max. one-half) of the sampling frequency. ADVANTAGE - Analog to digital conversion of detection signal for digital processing is adjusted for speed so that signal-sampling instant is related to distance travelled.