Associated with maximum output is a maximum ring-on of the signal which narrows the bandwidth and increases the pulse duration thereby reducing temporal resolution. But this is not always the best situation for all aspects of NDT. that tuning the pulse-duration to the natural frequency of the probe provides the maximum amplitude output. Your video also illustrated the effect that is most obvious i.e.
#Bipolar square wave driver#
It was my experience that the maximum output I could generate was when using a square wave and no real advantage was had using a Sine wave as the driver shape. This allowed me to experiment with different pulse shapes (Square, sine, saw-tooth, etc.).
#Bipolar square wave generator#
The typical signal generator can provide 20Vpp (which is adequate for research work) and for my early work I used it in continuous mode.which can result in a lot of heat being generated by the probe even at 20Vpp. Long ago now, when I was first experimenting with schlieren visualisation of ultrasound, I used my signal generator without an amplifier to pulse probes.
ĭaniel, these videos are an excellent example of the use of the pulser to tune the pulse. Re: What is square wave ? In Reply to Daniel Braun at 12:12 Feb-27-2017. R & D, Materials Research Institute, Canada, Joined Nov 1998, 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 ) 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 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 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. Re: What is square wave ? In Reply to ST.
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