In a message dated 2006/11/29, tchannel@.............. writes:

> I am still trying to eliminate my daytime noise, or at least identify it. 
> It was suggested I remove the magnet from the coil area to see if the noise 
> continued, if so it might be electrical, like RF, communications etc. using the 
> coil and cables as antenna. During a noisy hour I remove the magnet, from 
> the coil.  All the noise disappeared, the helicorer was just a flat line. After 
> a while, I reinstalled the magnet surrounding the coil and the noise 
> reappeared. Note: I only get these spikes between 8am and 5pm, the night time hours 
> are very quiet.
> Q.  Should I conclude that this means that it can not be electrical, ie, 
> radio interference, but must be something creating vibrations?

 Hi Ted,

       This suggests very strongly that it is not RFI or pulse feedback from 
the power wiring. 
       What is the construction of your seismometer? Is the pickup coil on 
the moving arm and the magnet on the floor / baseplate?

> Q. On a different subject. Thanks to your input, I now have a better 
> understanding of LaCoste zero length spring suspension, and how it is applied.
> But I don't understand (what is zero length) or how to find if a spring is 
> zero length.  Perhaps someone could walk me thru this using a "screen door 
> spring" as an example.

       Extension springs are wound with a considerable internal tension - you 
have to pull them fairly hard to get them to extend at all. 
       You hang the spring vertically and measure the distance between the 
loop ends. Then you add just enought weight to start to extend the spring, 
measure the separation, increase the weight etc until you have maybe 5 points of 
length vs weight. Then you plot the points on a graph and extend the line 
joining them back to the axis. If the line passes through the zero weight / zero 
length point, you have a zero length spring. Hopefully, it will give a -ve length 
for a zero load.

       Regards,

       Chris Chapman
In a me=
ssage dated 2006/11/29, tchannel@.............. writes:



I am still trying to eliminate=20=
my daytime noise, or at least identify it. It was suggested I remove the mag=
net from the coil area to see if the noise continued, if so it might be elec=
trical, like RF, communications etc. using the coil and cables as antenna. D=
uring a noisy hour I remove the magnet, from the coil.  All the noise d=
isappeared, the helicorer was just a flat line. After a while, I reinstalled=
 the magnet surrounding the coil and the noise reappeared. Note: I only get=20=
these spikes between 8am and 5pm, the night time hours are very quiet.

Q.  Should I conclude that this means that it can not be electrical, i=
e, radio interference, but must be something creating vibrations?



 Hi Ted,



       This suggests very strongly that it is=20=
not RFI or pulse feedback from the power wiring. 

       What is the construction of your seismo=
meter? Is the pickup coil on the moving arm and the magnet on the floor / ba=
seplate?



Q. On a different subject. Tha=
nks to your input, I now have a better understanding of LaCoste zero length=20=
spring suspension, and how it is applied.

But I don't understand (what is zero length) or how to find if a spring is=20=
zero length.  Perhaps someone could walk me thru this using a "screen d=
oor spring" as an example.




       Extension springs are wound with a cons=
iderable internal tension - you have to pull them fairly hard to get them to=
 extend at all. 

       You hang the spring vertically and meas=
ure the distance between the loop ends. Then you add just enought weight to=20=
start to extend the spring, measure the separation, increase the weight etc=20=
until you have maybe 5 points of length vs weight. Then you plot the points=20=
on a graph and extend the line joining them back to the axis. If the line pa=
sses through the zero weight / zero length point, you have a zero length spr=
ing. Hopefully, it will give a -ve length for a zero load.



       Regards,



       Chris Chapman