>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 17 February 2006 17:02
>To: Microcontroller discussion list - Public.
>Subject: Re: [EE] Distance Measurement
>
>
>Michael wrote regarding 'RE: [EE] Distance Measurement' on 
>Fri, Feb 17 at 10:12:
>> I'm wondering if high frequency vibrations from the engines 
>could play 
>> havoc with ultrasonics, and water splashing up will certainly cause 
>> problems with reflections, though those can probably be filtered out.
>> 
>> The only viable alternative I can think of would be a laser based 
>> system, which would also have problems with water splashes, but at 
>> least should be more immune to vibration.
>
>The motors shouldn't be vibrating in the ultrasonic range, 
>should they?  And wouldn't vibration be a bigger problem for a 
>focused beam of light than a high frequency sound wave?

You can get get significant amounts of ultrasonic frequencies from an engine and it's ancilaries.  Even a humble ball race spinning produces ultrasonic vibration, as would any cavitation at the props.

Regards

Mike

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