A,B,C SCANNING MODES

A SCAN

Ultrasonic testing can be done using various modes, A scan is most widely used among them,wich can be called as one of the common testing techniqes in manual ultrasonic testing.the reflected energy either from a defect or the back wall of a specimen are displayed as signals on the CRT display.
there are two axis on the flaw detector screen wich is x- axis and y- axis. the x-axis represents the time or distance where as the y-axis represents the signal amplitude or the energy of the returning echoes from the specimen.
In this system the size of a defect can be analysed by looking into the amplitude of the returning echoes and defect location can be understood by the positioning of the echoes on the time or distance base, and also type of the defect can be analysed by giving a lateral as well as swivel scan on the test material and thus it produces the corresponding shapes in echoes wich helps in easily identifying the type of defect.
Overall we can say that by this method you can get  size ,shape and depth of the defect using A-scan method.

B SCAN

The B-scan system gives us  a cross sectional view or end view of the test material under scan.here the  depth of the defects can its linear dimensions can be accurately evaluated.the time taken by the sound wave to travel is displayed on the y-axis and the position of the probe placement is shown on the x-axis of the display.

C SCAN 

This method gives us a plan view and also size of the total test specimen.the defects are shown as a contrasting areas on a printout wich is related to the probes movement over the surface.