# Long Range Narrow Beam Ultrasonic

sirch: Grumpy_Mike - Thanks for the reply but I would need some convincing. As I see it the thing is that a radio wave is polarised and so a Yagi only needs to work in the direction of the polarisation but the ultrasonic is not polarised and so needs to be 2 dimentional.

Sirch, I agree with you. The array you are talking about is more like a diffraction grating or a synthetic aperture radar than a yagi array.

PS - there are a links to a couple of papers at http://en.wikipedia.org/wiki/Synthetic_aperture_sonar.

PPS - a phased array http://en.wikipedia.org/wiki/Beamforming is closer to what you are talking about.

dc42 - thanks for that, those links are really helpful.

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.

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

sirch: 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.

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.

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.

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

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: 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.

cr0sh: 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.

sirch: 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.

cr0sh:
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.

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.....

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.

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

How about Plan B?

sonnyyu: 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

GM100DU is integrated with mOS V1.

mOS V1 Visible software As an advanced e-product, mOSV 1.0 visible system is specified for laser measurement platform, which makes hardware and software works perfectly and allows users have amazing experience. Now the question is if mOS support USB port control.