Method for measuring displacements, in particular for the absolute measurement of short displacements, via the propagation time of pulses in a material support medium, and associated device for carrying out the method

The invention relates to a method for measuring displacements by means of the propagation time of pulses in a support medium by means of a calibration section and a measurement section, which are traversed by a pulse which, upon reception, is converted in each case into an electric signal. The sections are each assigned an electronic pulse count store (integrated-demand memory) which are started at the beginning of the propagation time of the pulse, are subjected during the propagation time to a high counting frequency, which they store, and are stopped at the end of the propagation time. The summing results of the pulse count stores are used to determine the relative measurement section length with respect to the calibration section length. For the purpose of absolute length measurement, the counting frequency is selected as a function of the rate of propagation of the pulse in accordance with the incremental measurement accuracy in such a way that the calibration section is subdivided by the counting frequency into the maximum number of increments, and the difference is formed from the contents of the pulse count stores. In the case of a support medium which is not constant, the counting frequency is selected in such a way that at the highest occurring rate of propagation of the pulse a number of counting pulses is still stored which is larger than required by the measurement accuracy. The quotient is formed from the incremental number of the measurement accuracy and the pulses counted in the pulse count store for the calibration section, and the pulse number in the measurement section pulse count store is applied to it. The result is equal to the absolute displacement in increments.