Chris-

I wanted to report on my recent activity with the tiltmeter (NOT the
tiltometer!).

Your last comment to me about the Linear LTC1043 circuit going unstable if
the Cx is smaller than the Cref has opened a door and I am now proceeding.
Knowing that the circuit was working was of great value and I stopped
trouble-shooting and have attached the circuit to the tiltmeter yesterday!
The instrument is amazingly stable, no apparent noise on the scope, no
sensitivity to moving my hands near the un-shielded Hg pots and it seems to
just simply work.

I did a simple sensitivy check. The plate the two pots are mounted on is
supported by screws in a triangle configuration (see
http://ntweb.mcn.org/gbush/Tiltmeter/Construction/Construction.html).
The pots are separated by 24" center-to-center, and the micrometer leveller
leg is separated from the other end two suppoort screws by 27 1/2". When I
adjusted the micrometer by .01" vertically, I got an output voltage change
reading of 0.193v. If my trig is correct this is the voltage change for a
tilt change of 6.347 -07 deg. I have no feeling if this is getting into the
ball-park of sensitivity needed to detect Earth tides. What sensitivity do
you think is needed?

Since yesterday afternoon I have periodically recorded output voltage and
time. This is the signal so far:

Date	Time	Vout
----	----	----
3-4-07	1:21p	1.625
	3:45p	1.594
	5:27p	1.605
	6:30p	1.615
4-4-07	9:29a	1.654

Presently I am connecting the instrument to my Windaq DI-194 to try to plot
daily signal variations. Then I will be able to see if I need to add
another stage of gain. After that, a complete mechanical tear-down to
shield the Hg cups and connecting tube and to build an insulated enclosure
with a heater in the top.

I can see light at the end of the tunnel and am really geting excited!


George
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