METHOD AND ARRANGEMENT FOR ELECTROMAGNETIC WAVE DISTANCE MEASUREMENT BY PULSE TRANSIT TIME METHOD

摘要

For electromagnetic wave distance measurement by the pulse transit time method short electromagnetic transmission pulses are emitted at periodic transmission instants. The signals received in selected transmission cycles after the respective transmission instants are sampled for obtaining in each of these transmission cycles a sample at a sampling instant in a respective sampling time interval, each sampling instant having a delay dictated by a sampling function relative to the respective transmission instant. The sampling instants exhibit differing delays relative to the respective transmission instant so that the samples in sequence produce an image of the sampled received signal extended in time. The sampling function dictating the delays is generated by a computing circuit, preferably a microcomputer, thus making it possible to make use of any sampling function and to modify sampling of the received signals in any way. More particularly, it is possible to measure the applied delays and to correct them to maintain predetermined design values. One sampling function which can be put to use to advantage in this method is a staircase function, each step of which has the length of several sampling time intervals.