From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: outside air temp sensor
Message-ID: <8svniv8jupl3o3ga6rh9b7v1p5altb4kfn@4ax.com>
Date: Sat, 02 Aug 2003 14:14:43 -0400

OEMs generally put the sensor in the lower part of the front quarter in front
of the radiator.  They don't have to be particularly worried about the
accuracy when the car is stopped.

Finding a good place on an RV is a challenge.  I spent quite a bit of time
figuring out something for mine.  Here are some of the challenges:

It should be radiation resistant (not respond to direct sunlight)
It should indicate the actual air temperature both stationary and while
underway.
It should not respond to heat soak from the rV body.
It should be shielded from the effects of road spray and debris.
It should not respond to heat sources in the rig.

The most accurate method is to mount a sensor in a radiation resistant mount
(designs are on the NWS web, I think) up high and out to the side of the rig,
far enough that convection from solar heating of the rig won't reach it.  Of
course, then it'll stick out far enough to snag things unless you put it
somewhere high on the front.  Then you have to make sure that heat from the
radiator when stopped doesn't affect it.

After experimenting with several locations, I finally mounted my sensor below
the front bumper in a polished stainless steel tube.  It is shielded from
radiator radiant heat by the lower skirt.  A second larger polished stainless
steel sleeve, tack-welded to the main tube with some air space in between
constitutes the radiation shield.  The indication only rises about a degree
from shade to direct sunlight.

The sensor is exposed to road spray but is protected by being epoxy potted
inside the tube.  The sensor output can be affected by road spray but I
decided that was a decent tradeoff. Plus it'll give me some indication of
incipient freezing conditions.

THe sensor in those cheap indoor/outdoor digital thermometers is a standard
10kohm thermistor.  You can run ordinary wire as far as you need to.  Use at
least twisted pair if the wire has to go near anything electrical or near the
engine.

John

On 01 Aug 2003 16:11:54 GMT, in rec.outdoors.rv-travel you wrote:

>Hi folks,
>            I'd like to install an inside outside temperature guage. It comes
>with an external probe. Question is where to install the probe to get ambient
>outside temps.
>          The probe will go through the fire wall but then the engine
>compartment is so hot. Any ideas. I see a space to the side of the radiator
>near the head light.
>Suggestions please.
>Tim,
>       Looking to expand Seniors (55 + ) Daytime Pool League


On 01 Aug 2003 16:11:54 GMT, timseniorspool@aol.com (Tim Dolan) wrote:

>Hi folks,
>            I'd like to install an inside outside temperature guage. It comes
>with an external probe. Question is where to install the probe to get ambient
>outside temps.
>          The probe will go through the fire wall but then the engine
>compartment is so hot. Any ideas. I see a space to the side of the radiator
>near the head light.
>Suggestions please.
>Tim,
>       Looking to expand Seniors (55 + ) Daytime Pool League