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Beam width!

A

Adam

Jan 1, 1970
0
Hello,
I have few 40kHz T and R ultrasonic transduces, and don't have any
info about thier beam width,
can anyone let me know how to measure their beam width please?

Thanks in advance
 
J

Jim Thompson

Jan 1, 1970
0
Hello,
I have few 40kHz T and R ultrasonic transduces, and don't have any
info about thier beam width,
can anyone let me know how to measure their beam width please?

Thanks in advance

If they're like the bunch I have in my junk box... pretty wide. I
used them as motion detectors for an alarm system design, and they
covered a 4' hallway within a few feet away from the transducer.

"Measure"? I don't know :-(

...Jim Thompson
 
R

Rene Tschaggelar

Jan 1, 1970
0
Adam said:
Hello,
I have few 40kHz T and R ultrasonic transduces, and don't have any
info about thier beam width,
can anyone let me know how to measure their beam width please?

Measure ... lets see, if you position both of them in
free space, meaning without refections from anything,
and have them rotateable around 3 axis,
then operating them should give you an idea. Beam
width means where the signal drops off by 3dB.

Rene
 
J

Joerg

Jan 1, 1970
0
Hello Adam,

I have few 40kHz T and R ultrasonic transduces, and don't have any
info about thier beam width,
can anyone let me know how to measure their beam width please?

Basically by CW transmission and then rotating the receiving tranducer
on a circular arch around the transmitter. Ideally you'd want a
professional sound pressure sensor as a receiver but a crystal should do
for a rough overview. Lots of web resources, such as this one:

http://www.ndt.net/article/v05n09/felix/felix.htm
 
Q

qrk

Jan 1, 1970
0
Hello,
I have few 40kHz T and R ultrasonic transduces, and don't have any
info about thier beam width,
can anyone let me know how to measure their beam width please?

Thanks in advance

You can get a rough idea about the beamwidth of simple circular
transducers with the following equation:

bw = 2*asin(lambda/(2*D))

where lambda = wavelength = c/f
D = diameter of the active face of the transducer

In air at room temp, lambda is appx (345 m/s)/(40kHz) = 0.00863 m =
8.63 mm.

Be sure wavelength and diameter use the same units (e.g. meters,
inches, rods, ...).

If you want a slightly more accurate answer, the "2" in the equation
is closer to 1.9436.
 
R

Rich Grise

Jan 1, 1970
0
Hello,
I have few 40kHz T and R ultrasonic transduces, and don't have any
info about thier beam width,
can anyone let me know how to measure their beam width please?

Thanks in advance

Set up a test bench in a soundproofed room - maybe hang blankets on
the walls or something, and ping the TX and move the RX around and
see what you get.

Good Luck!
Rich
 
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