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High precision short range distance measurement and monitoring solution

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Newbie level 1
Jan 16, 2013
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Hello All,
As a newbie in our forum, I honestly haven’t got much experience in any electronic projects in the past. So please bear with me.
I have recently been asked to provide a solution for monitoring the misalignment (distance) of two objects within a short range (up to 30 cm). My task is to propose a cost effective solution that can monitor the distance between these objects and also meet requirements as shown below:
1. Accuracy: <= 0.1 mm
2. Update rate: >= 100 times/second
3. Maximum distance range: < 30 cm
Can I use ultrasonic distance sensors (mount trigger and receiver on these objects separately) for this task? If yes, where should I start? If not, which other solution I could consider? Any comments or suggestions will be much appreciated

you can use a distance sensor such as this one
(this sensor seems low in order to your update rate requirements and it is not ultrasonic it depends on IRED (infrared emitting diode.... you can also design your sensor yourself but won't be such high accuracy )
This sensor will be connected to the microcontroller in order to doing analysis for your data ....and will need to calibrate your system

I doubt you will get 1mm accuracy with the Sharp sensor, let alone 0.1mm.

I cannot see ultrasound being viable for that sort of accuracy.

I would have said light was your best option. A coherent laser source using interferometry would be the most accurate but expensive and incremental.

A modulated laser phase shift system might be the best choice. The Bosch laser tape measures use that although for longer distance and worse accuracy. Some sort of internal reference/calibration could improve on that. It is not a trivial project though.


A row of tiny photosensors. This is manufactured commercially although I don't know if they are as long as 30 cm, or spaced as close as .1 mm.

To measure separation you would poll all sensors to find out which are shaded and which are not.

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