[time-nuts] 31bit ADC, 1000 samples per second

Poul-Henning Kamp phk at phk.freebsd.dk
Mon Dec 10 23:01:49 UTC 2012

In message <tilcc892a6ntfk64t2nljm92idr92df078 at 4ax.com>, David writes:

>The gain drift is specified at 2ppm per degree C.  There are
>provisions for a calibration cycle but that requires external

That's the really smart thing about this particular chip:  You can
drive the geophone calibration signal in through the second input
and out onto the first, which eliminates the external calibration
mux and the errors that usually cause.

And yes, in seismology you do care about frequencies from 0.1Hz and up
(0.01Hz if you're involved with the CTBT) and most voltage references
will be stable enough for that.

For longer term you calibrate your entire system, starting with the
geophone, so the voltage reference is caught that way.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

More information about the time-nuts mailing list