NetNews Usenet Archive 1993 #1/NN_1993_1.iso/spool/sci/electron/21968

Internet Message Format | 1993-01-05 | 2.2 KB

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From: [e-mail]
Newsgroups: sci.electronics
Subject: Re: Where to mount an outside temp probe on a car?
Date: 4 Jan 1993 21:32:45 -0600
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! From: [e-mail] (John Schuch)
!
! In article <[e-mail]> [e-mail] (Bruce G. Bostwick) writes:
! >In article <[e-mail]>,
! >[e-mail] (John Schuch) writes:
! >|>In article <[e-mail]> [e-mail] (Jim
! >"Throw it over the wall" Washer) writes:
! >|>>I'd like to mount a temp probe on my car to sample the air temp. I'd like
! >|>>to get as accurate a reading as possible (without exceeding some reasonable
! >|>
! >|>I think I'd try either in the trunk, or inside one of the tail-light
! >|>assemblies first. At sixty miles per hour, the airstream hitting the
! >|>sensor will cool it nearly as much as being wet. You need to find
! >
! >BZZZT!   He _wanted_ the air temperature -- which means he _wants_ _maximum_
! >"cooling" of the sensor.
! >
!
! Excuse me but if you cool the sensor by placing it in an airstream, your
! not reading the actual temperature of the air. Reading a sensor cooled
! by an airstream, by itself, tells you nothing. If you measure one sensor
! in an airstream and another one nearby but shielded from the air stream,
! you can determine the speed of the airstream. Other than that, I don't
! know why you would want to cool the sensor.
!
! You will note that weather stations keep the thermometer in a little
! louvered box to break-up the wind. Even high-end indoor/outdoor
! thermometers include a little shell to place over the external
! sensor.
!
! John
!
!


Being "cooled" by the air stream is exactly what is desired.  This will cause
the sensor's temperature to be the same as the air's temperature.

Unless the sensor hapens to be a warm blooded organism, there is no wind-chill
effect. The only error you can get is evaporative cooling, and if you keep it
dry, that will not occur.


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