## PSN-L Email List Message

Subject: Re: Thermal Control for Sensors
From: "Dewayne" n0ssy@...........
Date: Sat, 17 Nov 2007 10:14:30 -0700

```I haven't been reading all the post about this topic, so this may have =

My vault is very simple. It's cardboard box that is covered with 2" =
Styrofoam. For thermal control I have 3 one gallon glass bottles(wide =
mouth) in the vault. In one of the bottles I have placed
a aquarium heater and set the temp to about 70degs. The other bottles =
act as a thermal mass.

Don't know if this is helpful or not.

Dewayne
----- Original Message -----=20
From: Jerry Payton=20
To: psn-l@.................
Sent: Saturday, November 17, 2007 9:15 AM
Subject: Re: Thermal Control for Sensors

Hi Pete, Chris and Others,

I failed to mention that my goal is for three instrument covers.

IDEA:   How about an inexpensive 12v battery charger, with a =
sufficient max current rating, wired to three separate 15 ohm 25w =
resistors mounted on an aluminum plate for proper heat dissipation? =20

If my math is right, that would be about 10 watts to each cover and a =
total of about 2.4 amps current demand on the charger

Jerry.

----- Original Message -----=20
From: Pete Rowe=20
To: psn-l@.................
Sent: Friday, November 16, 2007 1:53 PM
Subject: Re: Thermal Control for Sensors

Hi Jerry
Since we don't know how well your insulation works, it
is hard to define how many watts you need to dissipate
to keep the inside of the box at a certain
temperature. I doubt that you need even 10 watts if
simple experiments. You'll need a thermometer inside
the box that you can read from the outside without
opening the box. Most any inexpensive indoor/outdoor
thermometers will be fine. Be aware that most of those
thermometers are only accurate to +/- 2 degrees C. For
this measurement that is ok.
Then get a 1 amp 12 volt DC wall wart and a 150 ohm 5
or 10 watt resistor. Put the resistor in your box and
hook up the 12 volts to it. The resistor will
dissipate about 1 watt (P=3D Esquared/R). Let it run for
a day and see if the temperature in the box goes up
and levels off. If this temp is ok, then you're done.
If you need more watts, calculate different resistors
for 2  or 5 watts and repeat the experiment. You
should find that you don't need a thermostat if you
sneak up on a fixed power dissipation that keeps the
temperature stable. If your insulation is very poor or
the outside temperature has large swings, then you'll
need more watts and a thermostat to cycle the heater.
It is best to avoid thermostats because they always
make electrical noise.
I hope this helps.
Pete Rowe
--- Jerry Payton  wrote:

> I am searching for wiring details for using Aluminum
> Housed Wirewound Power=20
> Resistors used for thermal control inside an
> insulated housing for the=20
> seismic sensors.  It has been suggested wiring
> several such resistors in=20
> series to accomplish a 10-30 watts from the 110v AC
> house supply source.=20
> I'm a little leery about the house current for
> safety reasons and possible=20
> AC hum.
>=20
> In studying the Mouser Electronics catalog, I can
> find several possible=20
> configurations using one to several resistors in
> series.  The resistors=20
> specify their wattage capability, but have different
> resistance values to=20
> choose from.
>=20
> If anyone has done this and has specific values
> etc., I'd appreciate hearing=20
> from you.
>=20
> Light bulbs attract bugs and other unwanted
> critters!
>=20
> Thank you,
> Jerry=20
>=20

=
_________________________________________________________________________=
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with Yahoo Mobile. Try it now.  =
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Public Seismic Network Mailing List (PSN-L)

To leave this list email PSN-L-REQUEST@.............. with=20
the body of the message (first line only): unsubscribe

I haven't been reading all the post =
topic, so this may have already been suggested

My vault is very simple. It's cardboard =
box that is=20
covered with 2" Styrofoam. For thermal control I have 3 one gallon glass =

bottles(wide mouth) in the vault. In one of the bottles I have=20
placed
a aquarium heater and set the temp to =
The other bottles act as a thermal mass.

Don't know if this is helpful or =
not.

Dewayne

----- Original Message -----
From:=20
Jerry =
Payton=20

To: psn-l@..............
Sent: Saturday, November 17, =
2007 9:15=20
AM
Subject: Re: Thermal Control =
for=20
Sensors

Hi Pete, Chris and Others,

I failed to mention that my goal is for three instrument =
covers.

IDEA:   How about an inexpensive 12v battery =
charger, with=20
a sufficient max current rating, wired to three separate 15 ohm =
25w=20
resistors mounted on an aluminum plate for proper heat =
dissipation? =20

If my math is right, that would be about 10 watts to each cover =
and a=20
total of about 2.4 amps current demand on the charger

Jerry.

----- Original Message -----=20
From: Pete =
Rowe
To: psn-l@..............
Sent: Friday, November 16, 2007 1:53 PM
Subject: Re: Thermal Control for Sensors
Hi JerrySince we don't know how well your =
insulation works,=20
itis hard to define how many watts you need to dissipateto =
keep the=20
inside of the box at a certaintemperature. I doubt that you need =
even 10=20

experiments. You'll need a thermometer insidethe box that you can =
from the outside withoutopening the box. Most any inexpensive=20
indoor/outdoorthermometers will be fine. Be aware that most of=20
thosethermometers are only accurate to +/- 2 degrees C. =
Forthis=20
measurement that is ok.Then get a 1 amp 12 volt DC wall wart and a =
150 ohm=20
5or 10 watt resistor. Put the resistor in your box andhook up =
the 12=20
volts to it. The resistor willdissipate about 1 watt (P=3D =
Esquared/R). Let=20
it run fora day and see if the temperature in the box goes =
upand=20
levels off. If this temp is ok, then you're done.If you need more =
watts,=20
calculate different resistorsfor 2  or 5 watts and repeat the =

experiment. Youshould find that you don't need a thermostat if=20
yousneak up on a fixed power dissipation that keeps =
thetemperature=20
stable. If your insulation is very poor orthe outside temperature =
has=20
large swings, then you'llneed more watts and a thermostat to cycle =
the=20
heater.It is best to avoid thermostats because they alwaysmake =

electrical noise.I hope this helps.Pete Rowe--- Jerry =
Payton=20
<gpayton880@.......>=20
wrote:> I am searching for wiring details for using=20
Aluminum> Housed Wirewound Power > Resistors used for =
thermal=20
control inside an> insulated housing for the > seismic=20
sensors.  It has been suggested wiring> several such =
resistors in=20
> series to accomplish a 10-30 watts from the 110v AC> =
house=20
supply source. > I'm a little leery about the house current =
for>=20
safety reasons and possible > AC hum.> > In =
studying the=20
Mouser Electronics catalog, I can> find several possible =
>=20
configurations using one to several resistors in> series.  =
The=20
resistors > specify their wattage capability, but have=20
different> resistance values to > choose from.> =
>=20
If anyone has done this and has specific values> etc., I'd =
appreciate=20
hearing > from you.> > Light bulbs attract bugs =
and other=20
unwanted> critters!> > Thank you,> Jerry =
>=20
=20
=
_________________________________________________________________________=
___________Be=20
a better sports nut!  Let your teams follow you with Yahoo =
Mobile.=20
Try it now.  http://mobile.yahoo.com/sports;_ylt=3DAt9_qDKvtAbMuh1G1SQtBI7ntAcJ=
__________________________________________________________Pub=
lic=20
Seismic Network Mailing List (PSN-L)To leave this list email =
PSN-L-REQUEST@...............
=20
with the body of the message (first line only): unsubscribeSee =
http://www.seismicnet.co=
m/maillist.html=20