Ray Gallant wrote:
> I would recommend a 100R or 1K platinum RTD.  About  $3.50 CDN.  You
> can get free samples on your own.  Spend your money on your front end
> and Vref accuracy.  Use a table derived from the available formulas
> for cold and warmer temperatures.  If you go that route check out
> DIN- EN60751 class-x and other standards.  The drift on some of these
> RTDs are minimum and if your circuit is very stable, you won't need
> to calibrate, just a verification is required.  You may need a DC
> offset due to the temperature range.  I use RTDs from Heraeus with
> great results.  You can also design a programmable home-grown
> temperature chamber (-30 to +30 deg C) for about 100 - $150 with a
> camper's cooler, darlington, relay & pic. Regards,  {slewrate}

The only problem with RTDs and NTCs is its top temperature.

The RTD Panasonic ERTD2FHL103S (Digikey $1.06) goes from -30 up to +125=B0=
C
only!!!

The NTC Thermometrics Global AL03006-5818-97-G1 (Digikey $2.66) goes
from -50 to +204=B0C (+400=B0F) only.
If you need to cook SMD, it needs to go at least to 450=B0F, obviously sh=
ould
operate at least up to 20% more, or, around 530=B0F.

A THERMOPILE is a nice non-contact sensor, that can measure the temperatu=
re
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 ambien=
t
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.
http://www.melexis.com website can give you more details about this chip.
They also have modules with complete solutions, digital or analog output,
but be aware of their $65 prices.

VV46NER

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