| 摘要 |
<p>A distance-amplitude compensation system for use in correcting the output from an ultrasonic pulse echo testing circuit. Prior to the testing of workpieces, ultrasonic pulses are applied to one or more test blocks having a plurality of equally sized reflectors positioned at varying depths therein. Ultrasonic pulse echoes returning from the reflectors are of differing amplitudes as a result of the near field and far field effects and attenuation of the test blocks. These echoes are transduced into electrical pulses and applied through a receiver to an oscilloscope display. A function generator provides a voltage vs. time curve which is also applied to the oscilloscope and is adjusted by the operator to conform to the peak amplitudes of the displayed electrical pulses. During subsequent testing, this voltage function is applied to a control signal generator which, in accordance with a predetermined relationship, modifies the voltage function into a control signal which is applied to the receiver. The control signal varies the receiver gain with time to attenuate and equalize the displayed pulses to a preselected amplitude. The equalized pulses corresponding to the equal sized reflectors are dependent upon only the size of the reflector and are independent of the depth of the discontinuities within the test blocks. As a result of the adjustment to the receiver gain by the control signal, the magnitudes of all displayed echo pulses from workpieces subsequently tested by the system will be dependent only upon the sizes of the corresponding discontinuities in the workpieces.</p> |
