At 10:41 PM 12/1/02 -0500, you wrote:

>The only problem with RTDs and NTCs is its top temperature.
>
>The RTD Panasonic ERTD2FHL103S (Digikey $1.06) goes from -30 up to +125=B0C
>only!!!

RTDs will go up to hundreds of degrees C. Whatever that part number is,
it is NOT an RTD, probably a thermistor.

>A THERMOPILE is a nice non-contact sensor, that can measure the temperature
>away of it.
>The MLX90247B (Digikey $13) in TO39 4 leads, generates 40uV/K and it
>incorporates a 26 kohms PTC in the same die, so you can compensate ambient
>temperature.  Even that operating temperatures should be from -40 to
>+150=B0C, this is the thermopile temperature, not the reading non contact
>temperature, even that I could not find its reading temp range.

That's interesting. Quite nonlinear output if it's the bolometer style.
They are much cheaper in high volume, but it's nice to see a source
for small quantities.

Thermocouples and RTDs are "almost" linear, in the case of RTDs,
linearity correction is easily done in hardware, of course in either
case you can use software. Because the nonlinearity is small (a few
percent) you don't need to worry about dynamic range of the front end.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the=
 reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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