# distance measurement

Jul 29, 2014
4
hey guys,
Gear I work with and repair gets down to 1mm but costs in excess of $35,000 cheers Dave #### GreenGiant Feb 9, 2012 842 I have been running into this same problem, I know of only a few range finders that will work over the 100m mark, though I have found a few in the 200m range, so if you can place 2 one on either side you could probably get that to work... The only problem is that they are around$1,200 each, you really are asking for a lot here.
What do you need it for?

#### Pranav R.

Jul 29, 2014
4
i want to use it in automobiles for some project
any thing other than lasers dat i can use fr distance measurement??
thank u for ur views

#### Pranav R.

Jul 29, 2014
4
any ideas other than lasers that would be reasonably prised and used for long range distance measurement??
cheers

#### shrtrnd

Jan 15, 2010
3,826
Nothing, for less than \$100.

#### BobK

Jan 5, 2010
7,682
From the 3D Robotics site:

With a proven 40 meter operating range

Bob

#### Laplace

Apr 4, 2010
1,252
You could build something for radio frequency ranging to measure the phase delay of a modulated carrier wave. The base station would transmit on a channel with an amplitude modulated tone. The mobile station would return the AM tone on a different channel. The phase delay of the tone would indicate the round trip transmission distance. The RF carrier propagates 1 meter in 3.3 nsec so the total round trip delay at 400 meters would be 2.7 μsec. The phase delay at maximum range needs to be less than one full cycle, so the maximum modulation frequency would have a period equal to the round trip delay, i.e., the maximum modulation frequency is 370 KHz. As the modulation frequency decreases, so does the potential accuracy. Just count up the nanoseconds and convert it to meters. Any time delay within the transmitter/receiver circuitry itself would need to be adjusted for at a known distance. Don't know what laws may apply to transmission of a carrier wave with ultrasonic tone modulation.

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