Dave Youden dyouden@.............
Sent: Mon, 16 May 2011 20:45
Subject: Photos
=20
Here is the link to the website where my pictures are posted.
ttp://marvelousmachines.blogspot.com/
David H. Youden
Hi David,
You have been busy! A few comments.
Can you check http://www.aspe.net/publications/Annual_2005/PAPERS/5FLEX=
/1859.PDF=20
please? I can't get it to display.
Good insulating screening boxes are essential. Trying to=20
control the seismometer temperatures may not be such a good idea.=20
The heaters, thermometers and control circuit often cause small=20
drifts / transients. It is very difficult to control the=20
temperature of a large enclosure with millidegree accuracy. It=20
is more effective to allow the seismometer temperature to drift=20
very slowly. =20
You can buy Al-Clad wirewound resistors which you can bolt onto=20
the Aluminum top-plates to heat them. If you put these plates INSIDE=20
the TOP of the clear plastic enclosures, they will stabilise the=20
internal air column. You only need a few watts of AC power. The=20
internal temperature will drift very slowly, but there will always=20
be a small positive internal air temperature gradient very=20
effectively inhibiting any convection.
Crossed foil suspensions are relatively difficult to construct=20
and they are not the quietest. Ordinary steel foil is liable to=20
corrosion. Stainless steel foil may be difficult to obtain.=20
Collect and cut up old electric shaver foils? Rolling foil and=20
wire suspensions are easy to make and have lower internal=20
friction losses eg a figure of 8 loop of fine wire glued around=20
two SS cylinders? You can buy fine Nickel plated music wire=20
from D'Addario.
Other suspensions which work well are circular section=20
crossed Tungsten Carbide rods and a flat, very hard Stainless=20
Steel plate rolling on a Stainless Steel ball bearing=20
(Smallparts). I use a large scalpel blade for the plate,=20
stuck to the end of the arm with two component Acrylic Glue.=20
This is tough, unlike Epoxy which tends to crack off smooth=20
surfaces.=20
What noise level were you able to obtain with your=20
electro-optical detector, please? I managed to get down to=20
about 14 nano metres using large area Si photo cells and a=20
temperature stabilised tungsten filament bulb.=20
Regards,
Chris Chapman=20
=
=
Here is the link to the website where my =
pictures are posted.
http://m=
arvelousmachines.blogspot.com/
David H. Youden
Hi David,
You have been busy! A few comments.
Can you check http://www.aspe.net/publications/Annual_2005/PAPERS/5FLEX/1859.PDF
please? I can't get it to display.<=
/PRE> Good insulating s=
creening boxes are essential. Trying to
control the seismometer temperatures may no=
t be such a good idea.
=
The heaters, thermometers and=
control circuit often cause small
drifts / transien=
ts. It is very difficult to control the
temperature of a large enclosure with millidegree accuracy. It
is more effective to allow the seismometer te=
mperature to drift
very slowly.
You can buy Al-Clad wirewound resistors which you can =
bolt onto
the Aluminum top-plates to heat them. If you put these plates INSIDE
the TOP of the clear plastic enclosures, they will stabi=
lise the
internal air column. You only need a few wa=
tts of AC power. The
internal temperature will drift very slowly, but there will always <=
/TT>
be a small positive internal =
air temperature gradient very
effectively inhibiting=
any convection.
Crossed foil suspensions are rela=
tively difficult to construct
and they are not the q=
uietest. Ordinary steel foil is liable to
corrosion. Stainless steel foil may be di=
fficult to obtain.
Collect and cut up old electric shaver foils? Rolling foil and
wire suspensions are e=
asy to make and have lower internal <=
/TT>
friction losses =
eg a figure of 8 loop of fine wire glued around
two =
SS cylinders? You can buy fine Nickel plated music wire
=
from D'Addario.
Other suspensio=
ns which work well are circular section
crossed Tungsten Carbide rods and a flat, v=
ery hard Stainless
Steel plate rolling on a Stainles=
s Steel ball bearing
(Smallparts). I use a large scalpel blade for the plate,
=
stuck to the end of the arm with two co=
mponent Acrylic Glue.
This is tough, unlike <=
/TT>Epoxy which tends to =
crack off smooth
surfaces.
What noise level were you able to obtain with your
electro-optical d=
etector, please? I managed to get down to
about 14 nano metres using large area Si =
photo cells and a
temperature stabilised tungsten filament bulb.
=
Regards, Chris Chapman