초록 ▼

The invention provides a method and an apparatus for determining the difference between the transit times of measuring pulse signals from a transmitter to a receiver along a measuring signal path establishing an unknown time of travel which is representative for a physical quantity of interest, and

The invention provides a method and an apparatus for determining the difference between the transit times of measuring pulse signals from a transmitter to a receiver along a measuring signal path establishing an unknown time of travel which is representative for a physical quantity of interest, and the transit times of reference pulse signals generated by the same transmitter and forwarded to the same receiver along a reference signal path establishing a known, constant time of travel, whereby for the measurement of each of said transit times the time distance between a trigger signal triggering the generation of the respective measuring pulse or reference pulse signal and a time-significant signal is measured which is generated in a defined time relation to the instant at which the respective pulse signal is received by said receiver. Both average values comprise non-linearity errors to the same extent so that these errors are eliminated when the second one of these average values is subtracted from the first one.

대표청구항 ▼

An apparatus for determining the difference between the transit times of measuring pulse signals of short duration being generated by a signal generating means and being forwarded therefrom along a measuring signal path which establishes for said measuring pulse signals an unknown time of travel bei

An apparatus for determining the difference between the transit times of measuring pulse signals of short duration being generated by a signal generating means and being forwarded therefrom along a measuring signal path which establishes for said measuring pulse signals an unknown time of travel being representative for a physical quantity of interest, and the transit times of reference pulse signals of short duration being also generated by said signal generating means and being forwarded therefrom along a reference signal path which establishes for said reference pulse signals a known constant time of travel, said apparatus comprising a signal receiving means for receiving said measuring pulse signals from said measuring signal path as well as said reference pulse signals from said reference signal path, and for generating on receipt of each of said measuring and reference pulse signals a time-significant output signal, and a time measuring device to which said time-significant output signals are supplied for measurement of the respective transit times, said time measuring device comprising a coarse transit time measuring means and a precision transit time measuring means consisting of a precision transit time measurement control means and of a time-to-amplitude converter circuit which is controlled by said control means and to which said time-significant signals are fed as start signals, said time-to-amplitude converter circuit providing an analog output signal the absolute magnitude of which, after receipt of each start signal, starts to increase with time from a zero value until a stop signal is supplied to said time-to-amplitude converter circuit, and wherein said apparatus further comprises: an oscillator means for generating a periodical time base signal having a highly constant frequency, a calibrating means for calibrating said time-to-amplitude converter circuit by measuring the increase of the amplitude of its output signal during a calibration time span having a defined length which is at least equal to the length of one waveform period of said time base signal, a control means for generating in synchronism with said time base signal n measuring pulse signals within a period of time during which the magnitude of said unknown transit time established by said measuring signal path does not change, and for generating in synchronism with said time base signal n reference pulse signals, the period of time during which said n measuring pulse signals and said n reference pulse signals are generated, being so short that the magnitudes of the response times of said signal generating means and of said signal receiving means do not change, a controllable delay means for imparting to each of at least n-1 of said n measuring pulse signals and to each of at least n-1 of said n reference pulse signals an individual additional predetermined delay before the corresponding time-significant signal is generated, the magnitudes of said at least n-1 delays for said at least n-1 measuring pulse signals being all different from one another and the magnitude of the longest of these delays being smaller than said defined length of said calibration time span, and the magnitudes of said at least n-1 delays for said at least n-1 reference pulse signals being all different from one another and the magnitude of the longest of these delays being smaller than said defined length of said calibration time span, wherein said precision transit time measurement control means is adapted to obtain for each of said n measuring pulse signals and each of said n reference pulse signals a precision transit time measurement value by forwarding to said time-to-amplitude converter circuit a start signal on receipt of a respective time-significant signal and by stopping said time-to-amplitude converter circuit in synchronism with the end of a predetermined waveform period of said time base signal occurring after said respective time-significant signal, wherein said apparatus further comprises an intermediate storing equipment for intermediately storing the thereby obtained n measuring pulse signal precision transit time measurement values and n reference pulse signal precision transit time measurement values, wherein said coarse time measuring means is adapted to obtain for at least one of said n measuring pulse signals and for at least one of said n reference pulse signals a respective coarse transit time measurement value by counting the waveform periods of said time base signal occurring between the waveform period to which the generation of said at least one measuring pulse signal is in synchronism and said predetermined subsequent waveform period at the end of which the corresponding precision transit time measurement is stopped, and by counting the waveform periods of said time base signal occurring between the waveform period to which the generation of said at least one reference pulse signal is in synchronism and said defined subsequent waveform period at the end of which the corresponding precision transit time measurement is stopped, respectively, and wherein said apparatus further comprises a calculating means for calculating the transit time difference of interest from the difference between said at least two coarse transit time measurment vaules and an average difference between said n measuring pulse signal precision transit time measurment values and said n reference pulse precision transit time measurment values, and a central sequence control means.