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Topic: Long Range Narrow Beam Ultrasonic (Read 14843 times) previous topic - next topic

sirch

Just thought I'd report back.

I've made a small hexagonal array of 7 transducers spaced 2Lambda apart (1 in the middle and 6 around) and it narrows the beam width from 70 degrees to about 30 degrees. Curiously there is a dip on the bore-sight.

Not that a small dip on the bore-sight really matters for my application but my thinking at the moment is that there is some acoustic coupling going on through the board that is causing interference and hence the dip.

GoForSmoke

My cheap unit has the transducers in open cylinders and has a 15 degree spread.

Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

dc42


I've made a small hexagonal array of 7 transducers spaced 2Lambda apart (1 in the middle and 6 around) and it narrows the beam width from 70 degrees to about 30 degrees. Curiously there is a dip on the bore-sight.


Did you make sure all the transducers are connected in the same phase?

Are the fronts of all the transducers flush with each other, in a plane perpendicular to the beam?

How far away from the transducers did you measure the beam width? If you measured it close to the transducers, you may need to set the center transducer back slightly, to equalize the distances between the transducers and the center of the beam at the measurement point, in order to avoid a dip in the centre.

It's many years since I studied physics, so I'm not sure that there isn't some mathematical reason why you should expect a dip in the center; however it doesn't sound right to me.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

sirch

The transducers are soldered flush on to a board and wired in parallel so they are reasonably in a plane and in phase as far as I can tell. When I get chance I'm going to try driving them at a slightly different frequency to reduce the chance of a standing wave since they are about 2 lambda apart.

I calculated that the far-field is about 2 feet away, I did the measurements about a foot away so I might try measuring further away.

sirch

OK tried doing the measurement in the far-field and the dip turns out to be just a near field effect. Also the -6dB beam width is 11degrees in the far field which is good.

cr0sh

Something I'm curious about: Will we ever see any of your code, schematics, or physical setup, sirch?
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

sonnyyu

#21
May 18, 2013, 09:48 pm Last Edit: May 18, 2013, 10:44 pm by sonnyyu Reason: 1
Ok Ultrasonic in Cave;-

We need meet following prerequisites:

1. Man's Best Friend: make sure dogs are happy with it, since all dogs can hear ultrasound.
2. No bother bats in cave. if there are. Bats use a variety of ultrasonic ranging (echolocation) techniques to detect their prey. They can detect frequencies beyond 100 kHz, possibly up to 200 kHz.


http://en.wikipedia.org/wiki/Ultrasound

I found bats are took care already, but how about dog?

scrotty digs = scrotty dogs, you got me. at least we have same concerned.

sonnyyu

#22
May 18, 2013, 09:51 pm Last Edit: May 18, 2013, 10:32 pm by sonnyyu Reason: 1

We have an other thread talk about water level measurement;-

The method is discussed at thread:

Ultrasound
Pressure sensor
X band Proximity Sensor
Ku band Proximity Sensor
K band Proximity Sensor
Sound
315MHz/433MHz rf-link Arduino (radio waves blocked by water)
Bluetooth Proximity Sensor
VLF radio waves (3-30 kHz) (radio waves through by water)
Laser-based water level sensor
Capacitance  proximity sensor
Resistance proximity sensor
Measurement the pump discharge pressure (if there is pump)
Float switch

http://arduino.cc/forum/index.php/topic,160378.0.html



at the thread, We are chatting about one single big transducer- electrostatic panels ( Made in UK) and flat ribbon drive even piezo buzzer for perfect in phase a flat wavefront.

sonnyyu

#23
May 18, 2013, 10:05 pm Last Edit: May 18, 2013, 10:28 pm by sonnyyu Reason: 1

Something I'm curious about: Will we ever see any of your code, schematics, or physical setup, sirch?

Same here,  I will be waiting few days for it since now is weekend, otherwise I will post very simple long range narrower beam laser implementation ( only use 2 ops + 1 dds + 1 ASIC  ) and hijack your thread.  :P

just kidding.

sonnyyu

#24
May 18, 2013, 10:23 pm Last Edit: May 18, 2013, 10:31 pm by sonnyyu Reason: 1

Yes, I have developed a laser based system (see the CREG Journal a couple of issues ago). The thing with laser systems is they are generally beyond me to integrate into a larger system (can't build a modulated or time-of-flight system and hacking something on to a ready build system is very hard, I've tried).


There are 3 major brands name laser based system - Fluke, Bosch, Leica. to make any of them to co-op with DIY or EDU application is tough, if not impossible. However there are so many Chinese made cheap systems, might come out few person shack... All we need is ASIC (application-specific integrated circuit).

Can you post your CREG Journal article? highly interesting.


sirch

#25
May 19, 2013, 12:34 pm Last Edit: May 19, 2013, 12:38 pm by sirch Reason: 1

Something I'm curious about: Will we ever see any of your code, schematics, or physical setup, sirch?


Most probably, most of my stuff is written up and my personal code is open sourced - http://interestingto.me.uk/

Thing is, you go to all that trouble and at best no one ever looks at it.

GoForSmoke

We do need a find and link-to resource. It's not easy to say the least to sift through the piles of posts and sites to research any topic. Perhaps a Wikipedia, even a card catalog.....

Nick Gammon on multitasking Arduinos:
1) http://gammon.com.au/blink
2) http://gammon.com.au/serial
3) http://gammon.com.au/interrupts

sonnyyu


Plan C;-



GM100DU  USB Photoelectric Laser Distance Meter

price: $100.00 USD qty

distance:100 M
accuracy: +/- 1.5 mm

search ebay, USB only no TTL UART.


sirch

Nice, shame it doesn't seem to have control via USB, only downloading measurement history.

sonnyyu

How about Plan B?

Plan B;-



LR4- Interface Board for Fluke 414D  Price: $149.00

FLUKE 414D   /Newark           Price: $129.95

Total: $280.00

http://www.porcupineelectronics.com/

distance:50 M
accuracy: +/- 2.0 mm



whole thread;- http://forum.arduino.cc/index.php?topic=169393.msg1260324#msg1260324

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