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I need to measure small distances (from 0-5mm) with precision upto 3 decimal places (like a micrometer). What sort of sensor can I use for this?

This is for measuring terminal heights. I understand that there are dedicated micrometers for this purpose but I'm wondering if there is a better way to do it electronically.

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Not worth an answer but capacitive sensing can be quite accurate for ranges 0-10mm. Also somewhat difficult to implement. Can't say what is "better" without knowing your requirements. – ACD Aug 20 '14 at 18:39
Does it have to be contactless? Are there any metallic surfaces involved? – venny Aug 20 '14 at 18:41
Not necessary for it to be contact less. Yes, metallic surfaces are involved. – Saad Aug 20 '14 at 18:43
Any idea what is the working principle of those 'touch micrometer' (mentioned by original poster) at 1 to 10 micro meter resolution? What resolution can highly refined LVDT do? – EEd Aug 21 '14 at 11:54

Check out LDC1000. It is inductance (not inductive) sensor IC, it only need external coil and capacitor to do 24-bit measurements in broad frequency range.

Edit: If this was a site about industrial automation, i would recommend to get a LVDT. But it is not.

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Interesting part, thanks. +1 – Spehro Pefhany Aug 20 '14 at 19:01
It's a nice chip this one +1 – Andy aka Aug 20 '14 at 19:17
Just cause it's used in industrial automation, doesn't mean an lvdt doesn't belong here :) +1 Also, that's a neat IC! Now I have to find a reason to use it! – bitsmack Aug 21 '14 at 6:53
@venny this is a nice chip but the issue is that the object's thickness that I have to measure is also conductive. I don't think this would work there. – Saad Aug 27 '14 at 9:19
The object, a wire terminal, whose thickness I have to measure after it is crimped, is also conductive. So I don't think this IC would work. – Saad Aug 27 '14 at 9:20

You can use a pair of digital calipers for about $15-20 and interface with the chip.

enter image description here

Interfacing with the chip is fairly straightforward and you can find examples on the net. Virtually all of the Chinese made calipers have a similar interface- a 1.5V serial stream of data. Famous Japanese brands such as Mitutoyo use a somewhat different scheme.

Internally these devices use a periodic pattern on a PCB substrate and a capacitive sensing scheme (originally developed by a Swiss company). They are not absolute measurement devices so you have to be able to zero them.

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Among other brands, this is one of many examples may be meeting your requirement, one factor is optical property of the pin to be measured. May be best to test a loaner unit before committed buy.

Mechanic touching sensor (caliper or the likes) is more tolerance to different type of objects. Optical can be more accurate, faster if it 'matches' the object property.

Dedicated micrometers or 'refined' caliper may be simple and better, but, since original poster ask for alternatives, optical worth trying out because if it 'matches' the object, it is higher accuracy, faster and clean (non touching).

You can buy off-the-shelf or if you want to design and make it yourself, the working principle is optical microscope with moving focusing. Focusing (as in turning the manual focus knob on traditional high-school microscope) is measured distance, but in highly refined version.

ZW-S30, measurement distance (sensor to object) is 27 to 33 mm, resolution 0.25 micro meter

This contacted type, from another brand, is 1 micro meter accuracy too. Does anyone know if its working principle is LDVT or like the above caliper?

another brand contacted device

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The Keyence product is a kind of absolute optical 'glass' scale system. – Spehro Pefhany Aug 21 '14 at 13:13

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