GB930689A - Measurement of dimensions of inaccessible bodies or structures by ultrasonics - Google Patents

Abstract

930,689. Anthropometrical appliances. KELVIN & HUGHES Ltd. Dec. 14, 1961 [Dec. 15, 1960], No. 43237/60. Class 81 (2). [Also in Group XL (c)] Apparatus for measuring dimensions of a foetal skull located within the uterus comprises a receiver 13 connected to receive echo pulses from an ultrasonic probe 10, two gating circuits 19 passing the receiver output during two spaced time intervals, means 14 for displaying the receiver output signals, a camera 36 arranged to photograph the display when its shutter is opened by solenoid 35, and means for opening the shutter in response to the passage through the gating circuits of signals of amplitudes exceeding predetermined values. Timebase generator 15 controls a unit 16 which generates pairs of gating pulses occurring at predetermined but adjustable times after the transmission of each pulse into the enveloping medium. If an echo pulse exceeding amplitude L1 occurs during the earlier gating pulse, normally-open contact 21 is closed; and similarly respecting contact 23. When these contacts close, capacitor 34 in the grid circuit of thyratron 24 charges through resistor 33 and after an adjustable time delay the thyratron conducts. Immediately on closure of contacts 21, 23 solenoid 35 is energized to open the camera shutter and a photograph of the cathode-ray tube (C.R.T.) display, Fig. 2, is taken; on thyratron conduction, contacts 31 open and the shutter closes. Thyratron cut-off is effected by pressing button 29. Means may be provided for feeding calibration pulses to the C.R.T.; and calibration of the apparatus may be made by using as a fixed standard a water tank having two reflecting targets.