In a message dated 04/04/2005, 1goss@........... writes:

> I would like very much to see detailed pictures of your setup. It would 
> help me to better understand the improvements you suggested.

HI Bryan,

       I am away from home at the moment, but I will do a sketch. I use a 
very different design. My concern when looking at your setup is to try to think 
what you can do to get your system to work well.

> I have 2 questions:
> 1. If you put the coil on the boom how do you keep the wire from interfering 
> with the swing or period.

       You run ordinary two core wire along the arm, taping it on every 6". 
Over the bearing you mount two vertical 'hairpin' shapes of the thinnest magnet 
wire that you can easily get, maybe 3" long. These are soldered between the 
cable on the arm and the cable from the baseplate to the amplifier. The amount 
of spring in them is tiny and should be ~constant. You can also wind ~10 turn 
coils onto a 3/16" rod and loop the free coil over the bearing. 
       RS sell 30G magnet wire and 30 gauge wrap wire. This is 10 thou dia, 
which is still a bit thick. I can get 5 thou wire wrap easily from other 
sources, but I use a reel of 2 thou which I bought many years ago. If you can get 
wire with polyurethane insulation, you can solder it directly using a hot iron. 
The insulation just melts.

> 2 I used 3/8 all thread, as you could see. I was afraid it would bend under 
> the weight as I noted the 4ft length of the rod was flexible when I bought 
> it.
> What size rod did you use? What size should I use? oops went over 2 
> questions.

       You should be able to get about 30" OK? What is the ~distance between 
the centre of the weight and the knife edge at the moment?
 
      I don't use 'all-thread' at all. I use 1/2" nominal stainless steel 
water pipe (~19/32") and brass compression water fittings, stop ends, Ts and Xs. 
I drill out the central hole of the T or X to give a clearance for the pipe.

> 3 My nightmare the only place I can put the seismograph is in my shop it is 
> very UN-level. I could not believe how much. It sets on sand near a ditch  
> when I level the boom their is over an inch difference from one end to the 
> other, this makes a hard job harder. 
> I had considered pouring a small amount of concrete to try and fix this.

       Ordinary concrete with gravel in it can be quite 'noisy' as the 
temperature changes, although 3' x 2' paving slabs have been used. The recommended 
mix is 50:50 cement and sand by volume. You mix it fairly wet and vibrate it if 
possible, to remove air bubbles. You cover it with polythene sheet for over a 
week to keep it wet and allow it to 'cure'. It may take a month to cure 
fully.

       What is your floor made of? It looks like wood block....

       What is the construction of your 'shop'?

       What is the ground material if you dig a hole outside? Do you get to 
solid rock at any practicable depth?

> also tonight late I had very little noise so it seems as their was no big 
> temperature contrast, this may well be the bigger problem. I ran FFT on the 
> low noise output of the seismograph and I clearly saw a spike the 6 sec 
> microseisms.

       You need to be able to see the 6 sec microseism peak quite clearly.

This is a good thing I right? but I am still going to improve it. 

       I can't see a 6 sec peak (0.17 Hz) on the FFT you posted. You read the 
frequency / period figures at the top of the screen for the ^ cursor 
position. It is the larger amplitude low frequency stuff between 0.1 and 0.01 Hz which 
concerns me. It is maybe 100x what it should be. I suspect that the noise is 
at least partially due to air currents, from your description. 
       Could it be partially due to your whole shop heating and cooling? Does 
it make any creaking noises? How does wind effect the signal?

       Regards,

       Chris Chapman
In a message dated 04/04/2005, 1gos=
s@........... writes:



I would like very much to see d=
etailed pictures of your setup. It would help me to better understand the im=
provements you suggested.



HI Bryan,



       I am away from home at the moment, but=20=
I will do a sketch. I use a very different design. My concern when looking a=
t your setup is to try to think what you can do to get your system to=
 work well.



I have 2 questions:

1. If you put the coil on the boom how do you keep the wire from interfering=
 with the swing or period.



       You run ordinary two core wire along t=
he arm, taping it on every 6". Over the bearing you mount two vertical 'hair=
pin' shapes of the thinnest magnet wire that you can easily get, maybe 3" lo=
ng. These are soldered between the cable on the arm and the cable from the b=
aseplate to the amplifier. The amount of spring in them is tiny and should b=
e ~constant. You can also wind ~10 turn coils onto a 3/16" rod and loop the=20=
free coil over the bearing. 

       RS sell 30G magnet wire and 30 gauge wr=
ap wire. This is 10 thou dia, which is still a bit thick. I can get 5 thou w=
ire wrap easily from other sources, but I use a reel of 2 thou which I bough=
t many years ago. If you can get wire with polyurethane insulation, you can=20=
solder it directly using a hot iron. The insulation just melts.



2 I used 3/8 all thread, as you=
 could see. I was afraid it would bend under the weight as I noted the 4ft l=
ength of the rod was flexible when I bought it.

What size rod did you use? What size should I use? oops went over 2 question=
s.



       You should be able to get about 30" OK=
? What is the ~distance between the centre of the weight and the knife edge=20=
at the moment?

 

      I don't use 'all-thread' at all. I use 1/2" n=
ominal stainless steel water pipe (~19/32") and brass compression water fitt=
ings, stop ends, Ts and Xs. I drill out the central hole of the T or X to gi=
ve a clearance for the pipe.



3 My nightmare the only place I=
 can put the seismograph is in my shop it is very UN-level. I could not beli=
eve how much. It sets on sand near a ditch  when I level the boom their=
 is over an inch difference from one end to the other, this makes a hard job=
 harder. 

I had considered pouring a small amount of concrete to try and fix this.



       Ordinary concrete with gravel in it ca=
n be quite 'noisy' as the temperature changes, although 3' x 2' paving slabs=
 have been used. The recommended mix is 50:50 cement and sand by volume. You=
 mix it fairly wet and vibrate it if possible, to remove air bubbles. You co=
ver it with polythene sheet for over a week to keep it wet and allow it to '=
cure'. It may take a month to cure fully.



       What is your floor made of? It looks li=
ke wood block....



       What is the construction of your 'shop'=
?



       What is the ground material if you dig=20=
a hole outside? Do you get to solid rock at any practicable depth?



also tonight late I had very li=
ttle noise so it seems as their was no big temperature contrast, this may we=
ll be the bigger problem. I ran FFT on the low noise output of the seismogra=
ph and I clearly saw a spike the 6 sec microseisms.



       You need to be able to see the 6 sec m=
icroseism peak quite clearly.



This is a good thing I right? but I am still going to improve it. 



       I can't see a 6 sec peak (0.17 Hz) on t=
he FFT you posted. You read the frequency / period figures at the top of the=
 screen for the ^ cursor position. It is the larger amplitude low frequency=20=
stuff between 0.1 and 0.01 Hz which concerns me. It is maybe 100x what it sh=
ould be. I suspect that the noise is at least partially due to air currents,=
 from your description. 

       Could it be partially due to your whole=
 shop heating and cooling? Does it make any creaking noises? How does wind e=
ffect the signal?



       Regards,



       Chris Chapman