Ultrasonic thickness measuring method and apparatus

The method of measuring the thickness of a workpiece by the ultrasonic pulse-echo method comprising:

• transmitting periodically an ultrasonic search pulse into the surface of the workpiece and receiving an echo pulse responsive to each such search pulse intercepting an acoustic impedance change;
• providing counts commensurate with the transit time of a respective search pulse traversing the workpiece thickness as determined by the time interval between a first signal being responsive to said search pulse intercepting the rear wall of the workpiece and a second signal being responsive to subsequent reflection of ultrasonic energy provided by said search pulse at the rear wall;
• accumulating the counts provided during successive such time intervals, and
• providing an output signal responsive to said accumulated counts when a predetermined programmable quantity of search pulses has been transmitted, said quantity being commensurate with the acoustic velocity of the workpiece.

An ultrasonic apparatus for measuring a dimension of a workpiece by periodically transmitting a search pulse into the workpiece and subsequently receiving an echo pulse responsive to the transmission of the search pulse, the combination of:

• a first clock for providing timing pulses;
• pulse generating means coupled for receiving said timing pulses and for providing in response thereto signals causing the periodic transmission of search pulses into the workpiece;
• receiver means coupled for receiving an echo responsive pulse in response to the transmission of a respective search pulse;
• timing means coupled for receiving a first signal responsive to the transmission of a search pulse and for subsequently receiving a second signal responsive to the echo responsive pulse associated with said search pulse and generating a timing signal commensurate with the distance traveled by said search pulse in the workpiece during the time interval between said first and second signals;
• a second clock for providing periodic clock pulses;
• counting means coupled for receiving said periodic clock pulses and for receiving said timing signal and providing in response thereto a third signal in the form of counts commensurate with the quantity of periodic clock pulses occurring during said timing signal;
• counter means coupled for receiving said third signal and subsequent third signals for accumulating counts commensurate with the respective quantity of periodic clock pulses occurring during successive timing signals;
• programmable counting means coupled to said first clock for receiving said timing pulses and providing a fourth signal when the quantity of said timing pulses received equals a programmed number commensurate with the sound velocity of the workpiece, and
• readout means coupled to said counter means and said programmable counting means for providing responsive to said fourth signal a readout commensurate with said accumulated counts.

An ultrasonic apparatus for measuring the thickness of a workpiece by periodically transmitting a search pulse into the workpiece and subsequently receiving echo pulses responsive to the transmission of the search pulse, the combination of:

• a first clock for providing timing pulses;
• pulse generating means coupled for receiving said timing pulses and for providing in response thereto signals causing the periodic transmission of search pulses into the workpiece;
• receiver means coupled for receiving a pair of echo responsive pulses in response to the transmission of a respective search pulse;
• timing means coupled for receiving a first signal being a rear wall responsive echo signal and a second signal being responsive to ultrasonic energy provided by said search signal subsequently intercepting the rear wall of the workpiece and generating a timing signal commensurate with the distance traveled by said search pulse in the workpiece during the time interval between said first and second signals;
• a second clock for providing periodic clock pulses;
• counting means coupled for receiving said periodic clock pulses and for receiving said timing signal and providing in response thereto a third signal in the form of counts commensurate with the quantity of periodic clock pulses occurring during said timing signal;
• counter means coupled for receiving said third signal and subsequent third signals for accumulating counts commensurate with the respective quantity of periodic clock pulses occurring during successive timing signals;
• programmable counting means coupled to said first clock for receiving said timing pulses and providing a fourth signal when the quantity of said timing pulses received equals a programmed number commensurate with the sound velocity of the workpiece, and
• readout means coupled to said counter means and said programmable counting means for providing responsive to said fourth signal a readout commensurate with said accumulated counts.