Defect detection in cylindrical objects

Claim 1

Method for detecting defects in a cylindrical test object having an axis, there being a stationary transmission and receiving device arranged about a path along which the said test object passes in an axial direction, comprising the steps of: providing a plurality of test cycles and one particular pulse per test cycle by means of a transmission portion of said device, said pulse splitting into two pulses which porpagate bi-directionally and circularly around said axis in said test object; receiving both splitted pulses once per circulation of each of the splitted pulses around the test object, so that a plurality of pulses appear in a receiver portion of said device in the test cycle, the amplitude of the splitted pulses gradually declining; providing a sequence of burst signals, each of limited duration, as reference signals for purposes of timing and gating, the bursts being repeated per said circulation on the basis of the expected propagation time between transmission and receiving portions providing peak detection of received splitted signals within limited periods of time, per circulation, in synchronism with said reference signals; digitizing the detected peak signals; and processing said digitized peak signals by forming the quotient of two sets of sequential peak signals in a test cycle.