From: Johannes Wolf (mp2100_at_mail-gw.estec.esa.int)
Date: Mon Aug 04 2003 - 23:54:17 PDT
Actually the Newt is measuring two temperatures at different locations:
one on the back of the LCD display
(very useful to adjust the contrast automatically using autoLCD)
one inside the rechargeable battery pack.
Since the temperature of the battery pack is strongly dependent on the
actual battery status (charging/discharging)this reading does not directly
reflect the ambient temperature.
The LCD display has a certain heat capacity, therefore in theory the
temperature reading of the LCD display should be slightly below ambient (in
case the Newt is brought from colder to warmer environment) or above ambient
(in case the Newt is brought back into a colder environment)
If the Newt is for a long time in the same environment and the ambient temp
is not changing much the LCD temperature should pretty good reflect the
ambient temperature.
In case the LCD temperature has a different reading this might be a
calibration issue.
Usually teh thermistor used for sensing the temp is part of a voltage
divider. This circuit can be calibrated. Tolerances of the resistor and the
thermistor may cause incorrect temperature readings.
Since we do not know the circuit diagram of the Newt this is all I can tell
so far to the hardware.
Another aspect is software. Of course you can perform a correction in
software. I do not know how this is realised in the Newt, maybe there is a
parameter that can be changed.
But I assume that this is deep down in the NOS.
Cheers
Johannes
> -----Original Message-----
> From: newtontalk-bounce_at_newtontalk.net
> [mailto:newtontalk-bounce_at_newtontalk.net]On Behalf Of Paul Guyot
> Sent: 05 August 2003 07:28
> To: newtontalk_at_newtontalk.net
> Subject: [NTLK] Correcting Newton temperature
> Hello all,
> with the current heat in Western Europe, I was looking at the
> temperature my web server unit gives. It says 36.86 C. I took the
> thermometer and it's rather 29 1/3, although maybe I should wait a
> little bit for it to reflect the temperature on my desk (still, it's
> quite hot for 7 in the morning).
> I was wondering if anyone tried to make a relation between Newton
> temperature and real temperature. If this relation is stables through
> time, if it is linear or some easy to compute relation, etc. It would
> be fun to actually correct the temperature. It seems to really depend
> on the Newton since my other Newton says 29.57 C (very close to
> reality).
> Paul
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