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
> 
> 
> 
> 
> 
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> This message was checked by NOD32 antivirus system.
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> 
> 
> ------------------------------------------------------------------------
> 
> 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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