Just a thought -

PT100 platinum resistors may be a better starting point for high accurate
temperature measurements due to their linearity.



      Russell McMahon
_____________________________

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What can one man* do?
Help the hungry at no cost to yourself!
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-----Original Message-----
From: Dean Biddle <d.biddle@MAILBOX.UQ.EDU.AU>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Wednesday, 16 February 2000 12:27
Subject: Calibration of NTC thermistor PIC based data


>Hi!
>
>Could those who work with temperature logging equipment please help.
>
>I have just completed a PIC based temperature data logger using a NTC
>thermistor as a sensor.  A PC interface program contains a regression
>routine to correct for the non-linear response of the NTC thermistor. I am
>aiming to calibrate the device for better than +/- 0.02 C.  The zero point
>should be no problem.  Has anyone experience with variations from 0 C due
to
>differences in purified water quality  (e.g. standard deionised, distilled
>or ultrapure)?
>
>The device is only required to measure temperatures between 0 and 50 C.  At
>100 C, there are too few TMR0 derived counts to use this temperature for
>calibration and I think it risky to depend on the accuracy of a
>mercury-in-glass thermometer.  Does anyone know of a high scale temperature
>reference around 50 +/- 0.02 C?
>