inductiveproximity-sensor
I am thinking of using the LDC1612 by TI to sense position over a 0 to 10mm range with an accuracy better than 100nm. I have been told this is possible by a TI engineer.
However, my question concerns relative dimensions of coil diameter and target. I am especially concerned with linearity of response, or the ability to linearize it either in circuit or mathematically.
Diameters – Is it best to have a coil>>target?
Does anyone here have any experience with this type of sensing?
Mouser's latest mailing mentioned this one: Vishay VCNL4000. For the price of the proximity sensor you also get an ambient light sensor. 4mm x 4mm, 0.75mm high, though it has three blobs on it which make it somewhat higher. Still looks like it's less than 3mm.
Detection range for the proximity sensor is only 20cm, though.
disclaimer: the mention of Mouser is not a shopping advice :-)
Pretty sure they use radar for adaptive cruise control in cars. Check this sensor out:
I've heard them called "headway sensors" or "radar headway sensors". There are other technologies like acoustic but I'm not sure if they'll have the range you're looking for. Laser could work but it's aim is pretty narrow, dust dirt and fog can get in the way etc.
Good Luck!
Best Answer
If your primary concern is linearity, here is an idea not mentioned in TI design guides that might work better for you. (or might not work at all, I am not an electrical engineer after all)
Use two coils, one at the bottom one at the top of your "metallic container". Wire them into one in opposite directions. If the coils are geometrically identical then their non-linearity should somewhat compensated each other, although with the price of reduced sensitivity.
Alternatively use two channels of the chip for two separate coils and combine (subtract one from the other) them in software, basically making differential sensor. This should actually double the sensitivity while also reducing non-linearity.