Hi,

The old Siemens KTY10 and new family are not expensive and very linear.

Fernando

-----Original Message-----
From: Erik Reikes <ereikes@XSILOGY.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Date: Ter¨a-feira, 21 de Dezembro de 1999 4:06
Subject: Re: Thermistors on a PIC A/D input.


>At 07:58 PM 12/20/99 -0200, Edson Brusque wrote:
>>Hello,
>>
>>    Reading the Microchip AN685 (Thermistors in Single Supply Temperature
>>Sensing Circuits), I've made this worksheet.
>>
>
>That thermistor has quite a non-linearity to it.  If you want any kind of
>accuracy on your top end you will need a higher resolution AD.  I'd suggest
>trying to find a flatter thermistor for your temp range.  I know they must
>exist, anyone know of thermistors with a 'more-linear' response in 0-100C?
>
>-Erik
>
>>Temp   Thermistor   Voltage   A/D result
>>(0C)     Res(Ohm)       (V)      (0-255)
>>   0     32650,80     1,172           60
>>   5     25398,50     1,412           72
>>  10     19903,50     1,672           85
>>  15     15714,00     1,944           99
>>  20     12493,70     2,223          113
>>  25     10000,00     2,500          128
>>  30      8056,00     2,769          141
>>  35      6530,10     3,025          154
>>  40      5324,90     3,263          166
>>  45      4366,90     3,480          177
>>  50      3601,00     3,676          187
>>  55      2985,10     3,851          196
>>  60      2487,10     4,004          204
>>  65      2082,30     4,138          211
>>  70      1751,60     4,255          217
>>  75      1480,12     4,355          222
>>  80      1256,17     4,442          227
>>  85      1070,58     4,516          230
>>  90       916,11     4,580          234
>>  95       786,99     4,635          236
>> 100       678,63     4,682          239
>>
>>    Now I need to make a routine to interpolate this table, so with the
A/D
>>result value I can calculate the temperature in 0C.
>>
>>    Have anyone already done this? In Assembler? Anyone can help me?
>>Please??? :^(
>>
>>    Best regards,
>>
>>    Brusque
>>__________________________________________________________________________
_
>>| | || |\| | || || |\|\ Edson Brusque :-^= (brusque@flynet.com.br)
>>| | || ||| | || || |||| Musician, Tech Consultant, Programmer, Developer
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>