Measure distance of devices via radio?

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Discussion Overview

The discussion centers around the feasibility of measuring the distance between two devices using radio signals, specifically focusing on achieving millimeter precision over a distance of up to 15 meters. Participants explore various methods and technologies that could potentially meet the precision requirement.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses skepticism about achieving millimeter accuracy with radio signals due to the high speed of light, suggesting that even the best logic circuits operate at the nanosecond level, making precise measurements challenging.
  • Another participant proposes the use of ultrasonics as a potential solution, noting that sound waves travel slower than radio waves and could allow for more accurate distance measurements if combined with radio signals.
  • A different participant mentions ultrasonic proximity sensors, indicating that while they can detect objects at a distance of 2 cm, they doubt the ability to measure changes as small as a millimeter.
  • One participant suggests that lasers might offer a viable alternative for achieving the desired resolution, hinting at the limitations of radar resolution based on signal wavelength.

Areas of Agreement / Disagreement

Participants generally do not agree on a single method that can achieve the required precision, with multiple competing views on the effectiveness of radio signals, ultrasonics, and lasers for distance measurement.

Contextual Notes

Participants express uncertainty regarding the capabilities of various technologies, particularly in relation to the precision of ultrasonic sensors and the challenges posed by the speed of radio signals. There are also unresolved questions about the practical implementation of suggested methods.

Who May Find This Useful

This discussion may be of interest to individuals exploring distance measurement technologies, particularly in applications requiring high precision, such as robotics or automotive sensors.

ghubben
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Hello,

I've got a question about distance measuring via radio.
I would like to measure the distance between two devices, relatively small ones, using radio and my question is how fine that measurement can be? The devices would be a maximum of say 15 metres apart and a preciseness of about a millimeter is needed. Is that possible with common circuits available?


I'm not an electrical engineer of any sort so please keep it in laymans terms.

Thanks!
//Fredrik
 
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I don't think you could expect that sort of accuracy from radio signals.

The problem is that radio signals travel VERY FAST.

The speed of light and radio waves is 300 000 000 meters a second.
So, that is 300 meters a microsecond and 0.3 meters or 300 mm per nanosecond.

And the best logic circuits we have are capable of operating at the nanosecond level.

Even then it would be a very difficult project.

There might be a low tech solution using a video camera above both objects, but the answer to your question is no, unfortunately.

Ultrasonics may be another way. A sound wave travels at about 340 meters a second.
That is about 0.34 millimeters per microsecond.
So, you could send out a radio signal that a sound pulse was on its way and then count the time until the sound pulse got to the second object.
The radio signal would take a negligible time to get there, so quite an accurate reading could be obtained.

Developing something like that would take time and expertise though.
 
Hi Fredrik,

Sorry, i am not the expert you looking for but just happen to see your posting and like to share some info with you.

What i know is that ultrasonic promixity sensors used by cars and robots can detect objects upto as near as 2cm, as shown in this webpage :

http://www.parallax.com/Store/Sensors/ObjectDetection/tabid/176/ProductID/92/List/1/Default.aspx?SortField=ProductName,ProductName

Unfortunately, i do not know how can it detect proximity changes as small a millimeter. Personally, i do not think it can as car sensors are not that sensitive, i suspect.
 
Lasers night be a possibility. The resolution of radar is limited to the wavelength of the signal.
 

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