Steve, that is a very good idea - I'm not all that concerned about true accuracy, just so I can tell a .1 from a .01 cap. You mention seeing change as you wave your hands about - is it stable enough?
I would be interested in building one of those - I do fool around with uC some - that would make a neat project to display on a LCD.
Thanks for posting.
Ken H>
--- In Homebrew_PCBs@yahoogroups.com, "alienrelics" <alienrelics@...> wrote:
>
> A couple of 555 timers makes a surprisingly accurate and sensitive capacitance meter. Uses your DMM in 200mV mode. In the lowest setting, 1mV = 1pF. Measures down to 0.1pF resolution, keeping in mind it isn't that accurate, but you can see the capacitance change as you wave your hands around.
>
> http://www.polyphoto.com/tutorials/ElectronicCircuits/
>
> Build it with parts from your junkbox for next to nothing.
>
> Or if you can program microcontrollers, do the same thing in software. Regular clock followed by a monostable, the cap under test is in the monostable. Measure the time it takes to charge the capacitor.
>
> Steve Greenfield