OT: laser/ultrasonic rangefinder module

[newguy]

Sorry for the off topic post, but this forum is not only a wealth of information relating to CCS/PICs, but also embedded h/w in general.

I'm trying to find a rangefinder module that can measure distance to a target with a usable range of around 30 cm up to 3 m. Power supply of 12V, at least 100 measurements per second, outdoor environment, -40C to 50C, 0 to 100% humidity, possibility of rain hitting the unit. The targets will not necessarily have surfaces which are perpendicular to the sensor, nor will they necessarily be good light reflectors. A rarther demanding situation, I know.

Output can be analog or digital (rs-232 or similar). What I have in mind is something like the handheld electronic tape measures in home improvement/hardware stores.

I'm strongly leaning toward an ultrasonic sensor (Senix looks like it has the best), but the only thing that I'm leery of is their susceptibility to turbulence. The environment where this will be used will not be free of turbulence.

I'd like to check out the laser distance measurement modules, but I can't find any information regarding price at all.

Has anyone used one of these beasties (laser unit)? What sort of price (ballpark) should I expect, and what manufacturer(s) should I check out?

[Felix Althaus]

Hello

[Ttelmah]

c, is the letter used to indicate the velocity of light, not the velocity of sound. It is just fractionally under 300000km/sec. the round trip time using light, is about 2 nano seconds.
The problem though is that to get resolution of perhaps a few cm, requires taking timings to an accuracy of a few pico seconds. This is why light based systems are relatively expensive. Typical starting prices in the $200 area for fairly basic units.
The velocity of sound in dry air at 0C, is 331.4m/sec. This limits the maximum sample rate to 55Hz using sound.

Best Wishes

[Felix Althaus]

Yeah, my calculation is for US, I'm sorry, I should' ve mention that...
I'm studying etech and we use c for any propagation speed. We get it from the context, if it means sound, light or whatever.
What's the correct symbol for the speed of sound?

Felix

[SherpaDoug]

In industrial sonar work we also use c for the speed of a wave through a media, whether it be air, water, steel, etc..
Robert J Urick, an esteemed author in oceanographic acoustics, uses c for the speed of sound in water in his textbook Principles of Underwater Sound published by McGraw-Hill (1967).
_________________
The search for better is endless. Instead simply find very good and get the job done.

[newguy]

[Ttelmah]

Interesting.
Quick look at three textbooks, and they all use 'v' for the velocity of sound, suffixed by the medium.
c is a defined constant, and just like 'g', you shouldn't really use it for anything else, unless this is clear from the context.

Best Wishes