AVR-Chat

On Sun, 03 Jul 2005 13:58:41 -0000 you wrote:

>I am doing a tach project and timing is important.
>
>As I understand, resonators are lower accuracy than crystals, and many
>resonators have internal caps.  Easier to install, and often not very
>important.
>
>I have wondered just how important the associated capacitors are for
>accuracy?
>
>But for the tach, timing becomes much more important.
>
>As I understand, there are two ways to go.
>
>count till you hit a number, then check how long it took. or to select
>a time period and count how many pulses occured in that window.
>
>If I'm missing something, please let me know.
>
>If anyone has anything that might help, I'd be glad to find out.
>
>So, the questions comes down to component selection.  For a tachometer
>with a rate up to 35khz, what would be a good choice ?

At 35,000Hz a crystal would give an error of only a couple of Hz. A resonator could be off by around
200Hz. It depends on your requirement.
--
Ralph Hilton
http://www.ralphhilton.org
C-Meter: http://www.cmeter.org
FZAOINT http://www.fzaoint.net