piclist 2012\02\07\153645a >
Thread: increasing sensitivity of a thermistor
www.piclist.com/techref/index.htm?key=increasing+sensitivity
picon face BY : alan smith email (remove spam text)



hi group..me again

I want to bounce something off the members.


So I have a board that I designed with a 10K
thermistor, but its feeding a 3.3V micro (and that is fixed...cant change this
part).  They have come back and asked for
a better resolution.   
Now a thermistor, it simply generates a voltage
as a divider with a source impedance of course.  As the temperature changes, the voltage that
is
generated across it changes, and the resolution
of what you can measure is going to be dependent on the source voltage as well
as the ADC resolution.
 
So the ONLY way to get better resolution is to
be able to increase the source voltage from 3.3V to 5V or use a higher
resolution ADC.  Now for either case, the
micro thats reading this is 3.3V, so using 5V is out of the question.
 
Sorta thinking....using a PIC running at 5V to
read the thermistor, and then either using a PWM output (with RC filter) to regenerate
a voltage of controlled steps over the temperature range they want to measure
(pretty sure its 0 to 100F) for the ADC in their part to measure.
 
Any  other possible clever ideas?
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