X-Y digitising plotter using acoustic waves - where pointing device emits pulses received at multiple sensors, pulse arrival time difference used to calculate coordinates

摘要

The x-y digitiser plotter uses a pointing device (NADEL) where the position of the device (NADEL) is displayed in digital x-y coordinates on a fixed plate. The pointing device emits acoustic waves which are picked up by a number of detectors measuring signal pulse arrival time. The plate is rectangular in form. The detectors are ceramic piezo-electric devices. The detector levels for pulse detection are set at a proportion of the signal level of the previous impulse received, by means of a sample and hold circuit, and with filtering. The coordinate of the pointing device (NADEL) is calculated from the time differences between the pulse arrival time at each pair of sensors.