Short range wireless distance measurement ?

Question

I want to dynamically measure the distance between a fixed object and another object that is moving slowly. The objects will never be more than 5ft from one another. Is this possible? Does the technology exist?

Answer 1

for a short distance using wireless radio frequency can not be achieved accurately because the formula is complicated.

normally they use radar principle like the police hiding in the bushes measuring the traveling speed of the cars. radar is a device ejecting ultrasonic sound and when the sound reflect back it measures the distance.

the bat is using the same principle to fly in the dark. the camera is using the same principle automatically adjust to compensate the distance. then there is submarine using radar and the hunting of shark etc, lots of applications. i don't know if they use that on the cars to avoid bumping and if the respond is fast enough to avoid accident.

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Answer 2

It depends on the resolution and accuracy you want. Radio solutions will require you to accurately measure phase by way of interference (because the distance is so short that transit-time measurements will be to technically complex to do well).

The easiest way is ultrasonic.  You can easily buy ultrasonic range-measurement devices that were originally intended for use in cars.  These have the ideal range for your stated use.  Try Radio Shack for a version that you can 'get at' the internals so you can adapt it to your needs.  

Answer 3

sure, they have laser measurement devices you can buy in a hardware store.

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