Broadband ultrasonic sensing 200kHz - 2Mhz - Page 1
Forum section: electronics / projects

author: voltsandjolts
author_rank: Unknown
timestamp: September 28, 2024, 10:02:59 am
content: This is for a particular test setup we want to build for evaluation purposes.Linearity over range not important, receive only, just want a visible signal on a spectrogram.I know very little about ultrasonics. When searching for commercial sensor options I see bandwidths of a few hundred kHz. Perhaps bandwidth is dictated by physical size of the piezo (PZT?) elements and one sensor covering 0.2-2MHz is not actually possible? What's the widest I could expect?Anyone have any experience of ultrasonics in this frequency range?

author: moffy
author_rank: Super Contributor
timestamp: September 28, 2024, 10:54:00 am
content: It depends on how the piezo will be coupled to what it is sensing, piezos have a mechanical resonance dependent upon their shape and size, small thin piezo disks will have higher self resonant frequencies than larger piezos. But if the small piezo is hard bonded to another material it will take on that materials resonant characteristics to a large extent AFAIK.

author: Someone
author_rank: Super Contributor
timestamp: September 28, 2024, 11:05:14 am
content: As above coupling energy to the piezo element is a significant challenge, but can be as simple as supergluing the face of a piezo disc in place. Amplification is often designed around lower frequency operation but if you're not stuck with off the shelf amplifiers it's relatively easy.

author: Marco
author_rank: Super Contributor
timestamp: September 28, 2024, 11:23:09 am
content: As a microphone you just use it well below resonance with a high impedance amplifier, problem solved. Broadband excitation is the harder part.

author: nfmax
author_rank: Super Contributor
timestamp: September 29, 2024, 11:20:06 am
content: Assuming you are working in water or something similar, and receive only (didn’t spot that at first), then you should look at PVDF transducers.https://www.ndt.net/article/rocky/rocky.htm] https://www.ndt.net/article/rocky/rocky.htm. They have the potential for very wide bandwidth, and flat frequency response when operating below resonance. Talk to a specialist manufacturer about your specific requirements.

author: CaptDon
author_rank: Super Contributor
timestamp: September 29, 2024, 03:14:20 pm
content: Are you using it as an audio and ultrasonic through the air listening device or will it be hard mounted to something like a bearing? if 'Through the air' operation is desired a couple hundred KHz will be the end point for sure. If hard mounted like a turbine bearing vibration sensor then you would look for wide bandwidth accelerometers. I have seen turbine bearing vibration plots going into the low MHz. As a side note on aero turbines, sometimes a bird strike sets off a chain of vibrations and the FADEC (full authority digital engine control) thinks it sees and engine coming apart and shuts it down where in reality it really only needs throttled down enough to let the vibrations subside and then gently ramped back up, something old pilots learned to do before FADEC's when a steep climb compressor stall occurred followed by some impressive backfires that sounds like the engine was about to leave the aircraft! Now that is some vibration!!