## PSN-L Email List Message

Subject: Re: Range of 4,5Hz geophone
From: ChrisAtUpw@.......
Date: Sun, 8 Jan 2006 13:29:59 EST

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In a message dated 08/01/2006, ian@........... writes:

I've  spent the afternoon replacing the desk lamp in the enclosure with 3
car  lights. I'm starting off by feeding them 5 volts from an old PC
power  supply. If that isn't warm enough then I'll switch to 12 volts.

Hi Ian,

There are two problems with using light bulbs. You  need to run them at
3/4 the rated voltage to get a very long life from them and  the glass
envelopes need to be kept cool. If the glass gets too hot, oxygen may  diffuse through
it and shorten the filament life. The other problem is that  insects, spiders
and small animals are attracted to a warmed  environment, particularly if it
is also  illuminated.
Power resistors with an Al case which can be bolted  onto an earthed Al
top plate in the enclosure and provided with soldered  connections are likely
to give the most satisfactory permanent solution.  Farnell and RS sell them.

Regards,

Chris Chapman

In a message dated 08/01/2006, ian@........... writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>I've=20
spent the afternoon replacing the desk lamp in the enclosure with 3 ca=
r=20
lights. I'm starting off by feeding them 5 volts from an old PC p=
ower=20
supply. If that isn't warm enough then I'll switch to 12 volts. =20

Hi Ian,

There are two problems with using light bulbs.=20=
You=20
need to run them at 3/4 the rated voltage to get a very long life from them=20=
and=20
the glass envelopes need to be kept cool. If the glass gets too hot, oxygen=20=
may=20
diffuse through it and shorten the filament life. The other problem is that=20
insects, spiders and small animals are attracted to a warmed=20
environment, particularly if it is also=20
illuminated.
Power resistors with an Al case which can be bo=
lted=20
onto an earthed Al top plate in the enclosure and provided with soldered=20
connections are likely to give the most satisfactory permanent solution=
..=20
Farnell and RS sell them.

Regards,

Chris Chapman
```