What is a Square Wave in Ultrasonic Testing

Square wave is a shape of the signal
In the UT instruments the shape of firing pulse may be either spike or unipolar square wave or bipolar square wave; for the square wave firing pulse the half wave duration is tunable whilst the rising and falling edges should be kept as short as possible; also the stability of the amplitude should be provided within entire half wave duration. The video below shows the 3 types of firing pulse noted above - at the time of capturing of the video the standard load of 50 Ohm was connected to the pulser terminal, not the probe


Upon the probe is connected the efficiency of the spike / unipolar and bipolar square wave may be understood based on the observation of the echo returned from the material - this is illustrated by the video below


The half wave duration around 1/(2F) in the firing pulse (pulse Width) provides the maximal efficiency (F is the actual frequency of the probe )

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