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Hello, I have some ultrasonic sensors (T & F 40kHz), Unfortunately there is not any info, mark or specification on them, the seller did not know any thing about them, but it seems they are made in China. Now I have to measure the beam width of them (specially the transmitters). Can anyone advice me how to do so please? Thanks for any input.
__________________ Good judgement comes from experience, experience comes from bad judgment | |
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| | #2 |
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Because they are 40kHz, assume 30 degrees radial bandwidth.
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did you make any math for it?
__________________ Good judgement comes from experience, experience comes from bad judgment | ||
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| | #4 |
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It isn't difficult for you to measure the beamwidth.
__________________ Uncle $crooge | |
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| | #5 |
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To measure the beamwidth, you will need an oscillator to drive the transmitter and a meter of some kind to measure the output of the receiver. Place the transmitter and receiver so that they are facing each other, make the distance between them about 1 metre (my best guess as a starting point). Turn on the oscillator and measure the output from the receiver. Physically turn the transmitter by 10degrees and measure the receiver output. Turn another 10 degrees and measure again. Turn...... you get the idea. Draw a graph of receiver output against rotation of the transmitter and you will be able to measure the beamwidth. Beware of reflections from other objects in the room, you could get some strange results. JimB
__________________ Experience is directly proportional to the value of the equipment ruined. | |
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| | #6 |
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If the seller didn't know anything about them and thinks they are made in China then they probably don't work. They are rejects thrown away by a real manufacturer. E-Bay is full of stuff like that. Some surplus joints too.
__________________ Uncle $crooge | |
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| | #7 |
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Are you sure that they aren't just measuring the beamwidth from different points/distances away from the arpature? Because I'm pretty sure the beam width is something mostly dictated by frequency, and the only things that really affect it are the width of the transducer which causes diffraction which makes the signal messier and wider. The beamwidth is also not a perfect triangle and is messy with lobes and stuff so depending where you measure it you may get different readings. Have you ever seen a polar coordinate graph of beamwidth measurement? Last edited by dknguyen; 16th October 2006 at 07:17 AM. | |
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| | #8 | ||||
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I am not sure if you are replying to my post, but I guess so. Anyway here goes. Quote:
There was a thread here some months ago where hydrophone resopnses were produced by moving a metal object in a cartesian coordinate manner wrt the transducer. Whatever works for you I guess. Quote:
Quote:
If you want to specify the beamwidth at some other response value, it needs to be stated. Quote:
See the attachment. I did a plot of an 40khz ultrasonic transducer under less than ideal conditions (transmitter and receiver were attached to a hard bench using Blu-Tac). Although the measurements were done by rotating the transducer, I have graphed the data in a cartesian manner, mainly because I was not able to batter the Excel Chart Wizard into submission! I did not want to produce a polat plot using may data. (I have never used it to produce a polar plot before). My results show a 3dB beamwidth of about 40 degrees. JimB
__________________ Experience is directly proportional to the value of the equipment ruined. | |||||
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| | #9 |
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Nice post, Jim. I've got a bunch of no-name us-transducers and have thought about measuring them. I guess I'm more interested in the measurement than the actual transducers. Did you do anything to try to reduce reflections? I thought about putting baffles around the receiver to discourage non-line-of-sight paths. by the way, I think you can use the radar chart format to produce a polar plot. just pad out the full circle with what ever min value you want. It's not perfect but it's useful. | |
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| | #10 | ||
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If I were to do this seriously, I would probably mount the transducers on stalks above the supporting surface. I would also cover the mounting surface with a soft foam mat. Quote:
JimB
__________________ Experience is directly proportional to the value of the equipment ruined. | |||
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| beam, measuring, width |
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