Ultrasonic measurement instrument

Claim 1

IN AN ACOUSTIC MEASURING INSTRUMENT COMPRISING A PULSE GENERATOR FOR GENERATING ENERGIZING PULSES OF FREQUENCY IN THE SONIC TO ULTRASONIC RANGE, AT LEAST ONE ELECTROACOUSTIC TRANSDUCER RESPONSIVE TO SAID ENERGIZING PULSES FOR INTRODUCING VIBRATIONAL WAVES IN SAID RANGE INTO A SOUND TRANSMITTING MATERIAL AND FOR DETECTING ECHOES ARISING FROM ACUSTICAL DISCONTINUITIES IN SAID MATERIAL, AND A READOUT ELEMENT CONNECTED TO SAID TRANSDUCER FOR RESPONDING TO BOTH SAID ENERGIZING PULSES AND SAID ECHOES, THE IMPROVEMENT WHICH COMPRISES, (A) A VARIABLE FREQUENCY MARKER OSCILLATOR PRODUCING SPACED MARKER PULSES AND MEANS FOR CONNECTING THE OUTPUT OF THE OSCILLATOR TO THE READOUT ELEMENT, (B) THE READOUT ELEMENT DISPLAYING THE PULSES ON A TIME BASE WHEREBY THE PERIOD BETWEEN SAID MARKER PULSES OF THE MARKER OSCILLATOR MAY BE MADE EQUAL TO, OR A KNOWN FUNCTION OF THE TIME BETWEEN ONE OF SAID ENERGIZING PULSE AND AN ECHO CORRESPONDING THERETO, (C) MEANS ACTUATED BY THE MARKER OSCILLATOR FOR SYNCHRONIZING THE PULSE GENERATOR AT A SUBMULTIPLE FREQUENCY OF SAID MARKER OSCILLATOR, AND (D) MEANS FOR MEASURING THE FREQUENCY OF THE MARKER OSCILLATOR.