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Subject: Re: ultra sonic measurement
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Date: 01/25/03 at 4:27 PM
Posted by: Adam
In Reply to: ultra sonic measurement posted by Gad on 01/21/03 at 8:07 PM:
I would recommend National Semiconductor 1982 Linear Databook/Industrial Blocks/LM1812 Ultrasonic Tranceiver data sheet. They claim for the IC ranges in water above 100 feet, but only ca. 20 feet in air.
I think it's hard to overcome some problems with ultrasonic high distance ranging:
- focusing the transmitter beam to get clean echo,
- temperature dependent sonic wave speed,
- errors caused by air movements (outdoors)
to name some I consider the most relevant. You could resort to radat/laser technique, but then again you would need very fast logic at short distance: radio wave/light passes a distance of 0.5m (forth and back) in ca. 3.3ns. This requires also transmitter and receiver with short pulse response, especially for good resolution.
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