Hi,

I now have my filter connected and have made some measurements:

The gain presented by the filter is actually around 1000 taking into account the
natural losses caused by the filtering.

The noise signal presented to my A/D is about 35 mV peak to peak.  This means 35
microV coming out of the tilt meter system which equates to about 300 nanoRad.  pk
to pk.

Plugging this noise figure into Sean's formula this works out to be a descernable
quake of 5.7 Mag for a signal to noise ratio of 20.  [I think I got the sums
right!]

I tried standing next to it, for > 20 seconds, about 2 feet away and at 45 degrees
to the axis of tilt.  This generated a signal of 130 mV pk to pk, or 6.2 microRad.

Correcting an earlier mistake, my A/D is set to +/- 200 mV 12 bits.

So, I'm just waiting for the next event...

Thanks

Ian Smith


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