SE307252B - - Google Patents

Abstract

1,035,763. Ultrasonic testing. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Feb. 1, 1963 [Feb. 7, 1962], No. 4793/62. Heading H4D. In an arrangement for measuring a physical characteristic of a body which is related to the velocity of sound in the body, such velocity is determined from the echoes produced by two spaced echo producing regions D and E in the body when ultrasonic waves are launched into the body in the form of pairs of pulses the pulses of each pair being separated by time intervals which, alternately, are greater than and less than a variable time interval To which is adjusted to equal twice the transmission time T for ultrasonic waves between the echo producing regions, i.e. To=2T. In operation, the echo from the second region E produced by the first pulse of a pulse pair of spacing To + # precedes and combines with the echo from the first region D produced by the second pulse of said pulse pair to form a first composite echo and the echo from the second region E produced by the first pulse of an adjacent pulse pair of spacing To - # lags and combines with the echo from the first region D produced by the second pulse of the adjacent pulse pair to form a second composite echo displaced from the first composite echo, the required condition of To=2T being obtained by adjusting the value of To to equalise the amplitudes and shapes of the first and second composite echoes as displayed on an oscilloscope 17. The physical characteristic may be temperature or physical phase (e.g. liquid or solid). In the case of temperature measurement the body comprises a molybdenum or rhenium probe 5, 7, of known sound velocity/ temperature characteristic, the two echo producing regions of which are constituted by a shoulder D and by the end E respectively. The probe is acoustically matched by a tapered rod 4 of graphite or alumina to a magnetostrictive member comprising a nickel tube 1 in which the ultrasonic pulse pairs are induced by means of a coil 2 and from which echo pulses are derived by means of a coil 3. Various alternative forms for the probe are described with reference to Figs. 3A to 3D (not shown).