HI

I am using an NTC which is at (2,260Kohm at 70c) and (1,980Kohm at 75c) the resistance difference is not that big between these two temperatures and using the NTC in series with a resistor as a voltage divider wont give much of a voltage change when jumping between these tow temps. Is there any trick to increase the voltage change while using a small resistance change ?

Please let me know if i haven't been clear

Thanks in advance

 

I am using an NTC which is at (2,260Kohm at 70c) and (1,980Kohm at 75c) the resistance difference is not that big...

That's nearly a 12 1/2 % change in resistance going for 70 to 75C -- not that small. What are you trying to accomplish?

 

Are you using a 12K ohms type @25C, you can use a different ntc value for a greater resistance change, like a 47K or 100K

http://www.vishay.com/docs/29048/ntcle203.pdf

 

That's nearly a 12 1/2 % change in resistance going for 70 to 75C -- not that small. What are you trying to accomplish?

I am building a simple temperature controller and i am currently to far away from a place where i can buy NTC electronics so i got to use what i have on hand, i got this NTC from an old Air condition unit so i don't know the specs of it, the way i got the values was by warming water and measuring the temperature with a thermocouple and using an ohm meter for the NTC

 

hi banzai,
This interactive thermistor Tool I wrote sometime ago could give you an idea on values.
http://www.electro-tech-online.com/tools/ThermPlotV2.php
E

EDIT:
Using that tool, I make the basic thermistor 12000R at 25C with a 'B' factor of 3800

 

Driving it with a current from a constant current source (such as from a transistor collector or drain) will maximize the voltage change with temperature. You can then amplify that with an op amp and offset the voltage (if necessary) to get the voltage change you want.

But even with a resistive (voltage divider) load you should get enough voltage difference to easily trip a comparator, if you an using ON/OFF switch to control the temperature.