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

https://www.youtube.com/watch?v=8HPKQ9gXooo&spfreload=10

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

https://www.youtube.com/watch?v=wyTTCLMNqXQ

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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