Hi there,
You'll probably find the input impedance presented by the ADC3 input is
not a short to ground, but a low enough to discharge of the capacitor
fairly rapidly. In my limited experience, I have found the ADC input
impedance to be fairly low, and it can affect the values captured by the
ADC if the output impedance is not small enough on the device that you
are connecting to the ADC input. One work around is to buffer the source
you wish to sample. You can use an opamp to do this. The opamp presents
a high input impedance (10^12 on some FET opamps) and would result in
virtually no loading to your source. Opamps typically have a low output
impedance meaning that when provided a suitable load (in your case an
ADC input) the voltage presented should remain true to the input
(provided this is a straight buffer). I gladly accept any corrections!!
Hope this helps,
Andrew
[EMAIL PROTECTED] wrote:
Hi i use tmote and tinyos 1.1 ; i must use ADC to sample a voltage on Capacitor
but i have a problem. In fact i use ADC3 and GND(of ADC) but this pin result
short-circuit when tmote is on. This is a big problem for me because the
capacitor discharge and i can't mesaure the really value. How can i resolve my
problem??
Thanks
------------------------------------------------------
Leggi GRATIS le tue mail con il telefonino i-mode™ di Wind
http://i-mode.wind.it/
_______________________________________________
Tinyos-help mailing list
[email protected]
https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
_______________________________________________
Tinyos-help mailing list
[email protected]
https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
