I have a project that requires encoding positions to about .1mm, and with a very strict power and space requirement.
Luckily, these digital caliper thingies seem to have exactly what I need:
They seem to be just right for my needs (slow response, medium accuracy, low profile). Trouble is that these are still a bit too clunky, even after taking off the jaws and LCD. So I was hoping that members here may know more than I. I'll share what I have found so far.
There's some good docs on these, including this article on the protocol that they seem to use:
https://www.electroschematics.com/digital-caliper/Another quick read on how the protocol differs based on the measurement mode:
https://www.instructables.com/Hacked-Digital-Vernier-Caliper-Using-Arduino/There's this wonderful project on re-engineering the stator portion of the caliper, but has nothing on the capacitive sensor:
https://www.instructables.com/Reengineering-the-Stator-of-a-Digital-Caliper/This video explains the very basics on the capacitive encoder inside:
https://www.youtube.com/watch?v=XLa5PICnxpg, but don't go into any sort of detail on the engineering or principles.
Finally, this short article seems to explain the digital communication protocol with an emphasis on the methodology:
http://www.shumatech.com/support/chinese_scales.htmWith these things in mind, here are my questions:
- What sort of sensor may one select to recreate this on one's own? It seems that presently the chip is something with 8 capacitive pads used for sensing, likely giving analog readings. This isn't something that we normally see on every day MCUs, and even specialized chips never seem to have 8 of these sensors.
- Which principles are these designed on? Specifically, how do they maintain such precision in their measurements with such low cost?
- Capacitive encoding isn't a new technology, why don't we see these systems sold on places such as digikey? I suspect that I may be searching in the wrong places, so please correct me if I'm wrong.
Thanks in advance!