Bryan,
It might also help to add insulation to the bottom of the box.  Of course
you have to have holes to let the seismo feet touch the floor
underneath, and it would have to be thin enough that there is 
no contact between the seismo and the insulation.

Jack



-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of BOB BARNS
Sent: Monday, April 04, 2005 9:48 AM
To: psn-l@..............
Subject: Re: noise

   You can perhaps eliminate convection in your box by attaching a 
heater to the underside of the lid.  This should stagnate the air since 
the air is hotter at the top.  I use an ordinary resistor supplied by a 
fairly large wall-wart.  The resistor dissapates about 10W.  A small 
lamp would also work.
   My box is 2" thick styrafoam which has excellant insulating 
properties.  If your box is less insulating, it may take more heater power.
   I probed the inside of my box with a thermistor and found 2-3 deg. F 
difference with the top being hotter.
   Bob Barns


1goss@........... wrote:
> I am having problems with noise during the night. Oddly it starts about
9:00pm and ends about 11:00 am.
> 
> 9:00pm WinSDR screenshot  https://home.comcast.net/~bryangoss/noise9pm.jpg
> 
> 11:00am WinSDR screenshot
https://home.comcast.net/~bryangoss/noise11am.jpg
> 
> I think these pictures will explain much more than I can.
> 
> I thought it could be because the shop has a concrete floor and the air in
the shop heats up to aournd 70F during the day and cools to around 36F at
night. I believe the slower cooling of the floor during the night could be
causing  convection in the box. I tried to seal the box off and covered it
with a blanket but that did not work. Could it be caused by the temperature
change in the mineral oil and the vertical dampener?
> 
> I ran FFT but to be honest, I'm not sure how to read it.
> 
> Thank you for any help you can offer.
> 
> Bryan S. Goss
> 
> 
> 
> 
> 
> __________ NOD32 1.1044 (20050402) Information __________
> 
> This message was checked by NOD32 antivirus system.
> http://www.nod32.com
> 
> 
> 
> ------------------------------------------------------------------------
> 
> Subject:
> Re: Got it going I think
> From:
> ChrisAtUpw@.......
> Date:
> Sun, 3 Apr 2005 00:37:47 +0000
> To:
> psn-l@..............
> 
> 
> In a message dated 02/04/2005, 1goss@........... writes:
> 
>> I got my Lehman Seismometer up and running I think I may have my gain 
>> set a bit high, But I think it is ok.
> 
> 
> 
> HI Bryan,
> 
>        It looks like you have a fairly high gain on the amplifier. I 
> suggest that you examine sections of the trace, do a FFT on it and check 
> to see if the ~six second ocean background is dominant or if there is a 
> lot of other noise. Try wedging the mass so that it can't move to check 
> on instrument noise? I can't tell much from the drumplot, since I don't 
> know how it was scaled. It doesn't show any waveforms or any peak 
> counts. You need to click on X-Scale at the top of the display and then 
> select 'counts'.
>        The display shows small deflections during the night, but much 
> larger ones during the 'working day'. Do you have a lot of traffic / 
> industrial noise?
> 
>        What sort of suspensions / bearings are you using? A 12 sec plot 
> doesn't give you much 'headroom' over the 6 sec microseisms.
> 
>        Regards,
> 
>        Chris Chapman

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