how to measure short distance <3mm

Pete · Guest

hi,

Can someone help me, how to measure a short distance (less than 3mm) ? hope someone knows where to start.

Pete

mkent · Joined: 09 Sep 2003 Posts: 37 Location: TN, USA

There are several methods. Do a search on LVDT (linear voltage differencial transformer) also try www.keyence.com They make optical devices. Bring a fat wallet. Merry Christmas and Great 2004 to all. Mick

Guest · Posted: Tue Dec 30, 2003 1:29 pm

We make an educational object tracking system, mostly for teaching physics. But, it's based on video input so you can "zoom in" to measure small distances. You could look at our Website www.AlbertisWindow.com, or if you want to tell me more about your application I could give you a more specific reply.

Guest · Posted: Tue Dec 30, 2003 2:20 pm

Try using a ruler .... or be more specific about your application ;-)

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

A ruler wouldn't work! You would need a set of calipers.

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

You might be able to use capacitance. It can be cheap and rugged, though it is usually used at <1mm. It depends on your budget and accuracy requirements.

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Hans Wedemeyer · Joined: 15 Sep 2003 Posts: 226

Look a the data sheet for the IR proximity detector I used in this design.

http://hans-w.com/RPM.gif

It is good for at least 3mm
If you scale the DC output with an op-amp then use the 10 bit ADC in the pic the resolution can be very good.

I also used the same sensor for a mouse button...

http://hans-w.com/Mouse_6.jpg

Happy new year...

Neutone · Joined: 08 Sep 2003 Posts: 839 Location: Houston

Guest · Posted: Mon Jan 05, 2004 2:48 am

Use a linear pot like a slider volume control from a radio (these are usually log taper, though.) 3 mm is really short. You may have resolution problems. Pots wear out and get noisy, too.