At 11:47 PM 2/7/2012, you wrote:
>Wheatstone bridge

What he's doing is effectively a bridge a la Sir Charles, with half
the bridge composed of series resistor and thermistor and the other half th=
e
switched capacitor array in the SAR ADC. The ADC measures the unbalance
(ratiometric to the supply voltage, conveniently, if the references are the
supply rails).

BTW, the more current you put through the thermistor, the more voltage
per degree you get, but also the more self-heating at a given temperature-
this should be considered to make sure it is not causing unacceptable error=
s.

Best regards,

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



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