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From: John Woodgate
Subject: Re: 100Hz from 25.6kHz crystal.
Date: Tue, 3 Dec 2002 23:27:10 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Tue, 3 Dec 2002 23:54:35 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that John Fields
wrote (in <email@example.com>) about '100Hz from 25.6kHz
crystal.', on Tue, 3 Dec 2002:
>I've got the data sheets for an Epson C-2 type 32768Hz and an Epson
>CA-310 4MHz crystal in front of me and here are some interesting
> TYPE FREQ TOL TEMPCO AGING SHOCK
> C-2 20ppm -0.04ppm/°C² 5ppm/yr 5ppm
> CA-310 30ppm +/- 0.714ppm/°C 5ppm/yr 10ppm
>In the tempco column, the C-2 data is exactly as taken from their
>data sheet, while the CA-310 is represented as +/-50ppm over the
>range of -10 to 60°C. on their data sheet. I don't really
>understand the notation for the C-2 tempco and that's the only
>reference they make to it on the data sheet, but if it really _is_
>0.04ppm, then it seems the C-2 is clearly a better crystal at
>32768Hz than the CA-310 is at 4MHz!
I would interpret the 'deg. C squared' symbol as meaning 'per deg. C per
deg C', i.e. that you have to multiply the 0.04 by the actual
temperature. So at 25 C you get -1 ppm/deg.C.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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