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. YoudenHi David,You have been busy! A few comments.Can you check http://www.aspe.net/publications/Annual_2005/PAPERS/5FLEX/1859.PDFplease? I can't get it to display.<= /PRE>Good insulating s= creening boxes are essential. Trying tocontrol the seismometer temperatures may no= t be such a good idea.= The heaters, thermometers and= control circuit often cause smalldrifts / transien= ts. It is very difficult to control thetemperature of a large enclosure with millidegree accuracy. Itis more effective to allow the seismometer te= mperature to driftvery 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 INSIDEthe TOP of the clear plastic enclosures, they will stabi= lise theinternal air column. You only need a few wa= tts of AC power. Theinternal temperature will drift very slowly, but there will always <= /TT>be a small positive internal = air temperature gradient veryeffectively inhibiting= any convection.Crossed foil suspensions are rela= tively difficult to constructand they are not the q= uietest. Ordinary steel foil is liable tocorrosion. 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 aroundtwo = SS cylinders? You can buy fine Nickel plated music wire=from D'Addario.Other suspensio= ns which work well are circular sectioncrossed Tungsten Carbide rods and a flat, v= ery hard StainlessSteel 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 = FONT>arm with two co= mponent Acrylic Glue.This is tough, unlike <= /TT>Epoxy which tends to = crack off smoothsurfaces.What noise level were you able to obtain with your = TT> electro-optical d= etector, please? I managed to get down toabout 14 nano metres using large area Si = photo cells and atemperature stabilised tungsten filament bulb.=Regards,= PRE>Chris Chapman