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NTC/PTC Thermistor Reading conversion

N

Neil

Jan 1, 1970
0
I have a setup that currently takes in a reading from an NTC
thermistor on a board as a safety lock-out if the board temperature
gets too high. The latest design has switched to using a PTC
thermistor due to some space/cost constraints.

I have a setup all ready that read in the old NTC thermistor - and the
PTC design may be temporary so I don't really want to modify it too
much. Is there anything in existance that takes in a signal from a
PTC thermistor and gives an output representing what the NTC would
have given? If not how difficult would it be for me to design this?
What would that involve?

Thanks
Neil
 
R

Robert Baer

Jan 1, 1970
0
Neil said:
I have a setup that currently takes in a reading from an NTC
thermistor on a board as a safety lock-out if the board temperature
gets too high. The latest design has switched to using a PTC
thermistor due to some space/cost constraints.

I have a setup all ready that read in the old NTC thermistor - and the
PTC design may be temporary so I don't really want to modify it too
much. Is there anything in existance that takes in a signal from a
PTC thermistor and gives an output representing what the NTC would
have given? If not how difficult would it be for me to design this?
What would that involve?

Thanks
Neil

Ther are a number of ICs that have a *linear* voltage output
porportional to temperature (most in degrees Centigrade).
And some makers have them available in SOT-23 which is about a small
as you can get without going to COB.
 
T

Tony Williams

Jan 1, 1970
0
I have a setup that currently takes in a reading from an NTC
thermistor on a board as a safety lock-out if the board
temperature gets too high. The latest design has switched to
using a PTC thermistor due to some space/cost constraints.
I have a setup all ready that read in the old NTC thermistor -
and the PTC design may be temporary so I don't really want to
modify it too much.

A good overtemp safety circuit will also be arranged to
lock-out at an apparent undertemp. This is done so that
it failsafes for sensor open or short circuit.

Such a circuit is then also easy to swap between NTC and
PTC sensors, just change some passive bridge values, as
required for the possible differing sensor resistances,
and adjust the "overtemp/undertemp" tripping points.
 
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