From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: temperature sensor
Date: Sat, 17 May 2008 02:59:17 -0400
Message-ID: <iqvs24t3oer0pjc62768g5ms6emol21mt7@4ax.com>

On Fri, 16 May 2008 21:05:28 -0400, Steve Wolf <news@w8iz.com> wrote:

>Among the most pervasive problem was when I bought a replacement clock
>for the house that had a remote sensor.  I set it all up expecting that
>the home external sensor would give me the proper outside temperature.
>Nope.  It read 65 degrees, about five degrees higher than it should.  Darn.
>
>A day or two later, it dawned on me that my daughter brought over a box
>of miscellaneous stuff.  Inside I found a temperature probe.  BINGO!  I
>pulled the batteries and all should be well, right?  Nope.  Two days
>later I went out to the motorhome and turned on the fridge in
>anticipation of a trip.  There it is!  I keep a remote in the freezer
>compartment.  Pulled those batteries in that remote sensor.  Nope.
>Turned out to be the neighbor's sensor.  I took my clock and sensor to
>another location and got them all matched up.  Brought it home and it
>read ... nothing.  Took it back to that same location without the sensor
>and ... yep, someone somewhere had a sensor.  I did finally get it
>matched up but I'm still not convinced if it is to mine or my neighbor's.
>
>Yeah, wireless sucked.  That doesn't happen with a wired device.

Strange.  I have two Accurites, one Atomix, one Lacrosse and a wireless grill
thermometer and they all live in harmony.  Of course, I understand how they
work and carefully follow their instructions.

All but the grill thermometer work the same so I bet they have the same chip
inside.  The grill thermometer works on a totally separate RF band and so
doesn't enter the equation.  This is how they work, confirmed by an email chat
with a tech support dude at LaCrosse.

When the indicator is powered up, it scans the channels for about 60 seconds.
If nothing new is heard, it locks onto the strongest existing signal it hears.
BUT!  If, during that interval, a NEW transmitter is heard, it locks onto that
one.  The reason is simple.  The instructions tell you to install the
batteries in the indicator unit and then within about a minute, install the
batteries in the sending unit.

When the sending unit powers up, it selects a random channel.  If it happens
to land on a channel already in use as indicated by abnormal readings on the
display unit, simply remove the batteries in both units for a few seconds and
repeat.

If you wait longer than the open listening period to install the sender
batteries AND there are no other signals present, the display unit will
usually lock on anyway and work properly.  BUT!  If you wait too long and your
display unit hears your neighbor's sender, it'll lock onto that signal and
ignore yours.  The key is to follow the directions.

I don't use a wireless unit in my RV because I consider the sender environment
to be too hostile.  Plus I dislike having to crawl on the ground to replace
the sender batteries.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: temperature sensor
Date: Sat, 17 May 2008 02:40:27 -0400
Message-ID: <72vs241ftcm6f802277so2ajshirbafr0d@4ax.com>

On Fri, 16 May 2008 17:19:59 -0400, "tim fm ct" <r.dolan@snet.net> wrote:

>I've had a temperature sensor for outside temp reading while on the road.
>The probe wire broke. I'd like to put in another outside sensor.
>I've got a class A MH and I'm interested in ideas from the group regarding
>the location of the probe so that engine temp doesn't effect it when not
>moving.
>Thanks in advance.
>                                 Tim fm CT

That's a major problem, one that I've spent considerable time on.  Keeping it
away from the influence of the engine heat, the coach's heat AND the sun's
heat is a challenge.

I finally decided to copy what many car manufacturers are doing and locate the
thermistor behind the front bumper.  To isolate it from solar heat, I enclosed
it in a double walled, white painted housing made from fruit juice cans that
closely emulates the NWS's standard housing design.

It is completely free from the influence of both the engine and generator heat
except in the rare occasion when the wind is gentle but blowing just right. It
is still slightly affected by sunlight, a degree or two, but I can live with
that.  I try to park with the sun at my back so I don't get awakened by the
dawn light.

If I ever take the thing out to rework it I'm going to include a little
thermal mass to cause the reading to be averaged over a short interval.
Probably a big blob of RTV.  That worked nicely with my Maxxair fan's
thermostat.

http://www.neon-john.com/RV/Electrical/Maxx_air_mods/Maxx_aire_mods.html

Photo toward the bottom of the page.

John