🚀 go-pugleaf

Hi there.

I have just started out on a small project and at this moment I am at the
point where I need a linear and rotational sensor with high accuracy
and the sensor should not be prone to wear down after a short while.
And the sensor would somehow be connected to my PIC chip
that would be continuously reading from the sensor and storing the
most recent value in the memory and later sending it of to wherever
I need it.

First I was thinking about the obvious choices.
A variable potentiometer. But high accuracy pots with long usage
lifetime costs way to much.
A IR diode & IR transistor in an light isolated slider tube. But that would
not give me linear results directly. And I think the that there would be
an accuracy problem.

After some thinking I came to the conclusion that capacitors would be
an excellent choice. The idea was mostly due to the digital calipers
I have. It has an accuracy of 0.01 mm and I read somewhere that
the sensor is essentially a linear capacitor strip running inside the
calipers slider. And I thought the actual electronics shouldn't be that
expensive as the caliper itself costs about 30$.

Also capacitor would  give me a more linear values than anything else
as long as the surface geometry of the variable capacitor would
increase linearly.

Essentially what I want is a primitive form of a capacitor meter.

Now the problem is that I have never done this before and I am not that
sure of how it would be done and I thought some of the guys here
may have come across similar problems.

I imagine that I could use a multivibrator (555 based circuit) and generate
and square pulse depending on a variable capacitor. And on the PIC
circuit just increment a number from 0 to N depending on the time it takes
between the pulse peaks that I get from the 555 circuit. Thus the resolution
of the meter would be up to the operating frequency of the PIC (?).

Would this be the way to go ?

I'm unsure of how accurate it would become.
Where are the primary places where the accuracy
could be lost ? Maybe in the 555 circuit ?

Could anyone here give me some pointers and
help out a newbie here... please....

thanks
//iman

ps. sorry for the crosspost.