NTC voltage divider

Discussion in 'General Electronics Chat' started by banzai, Oct 28, 2014.

  1. banzai

    Thread Starter Member

    Jan 3, 2014

    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
    Last edited: Oct 28, 2014
  2. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    That's nearly a 12 1/2 % change in resistance going for 70 to 75C -- not that small. What are you trying to accomplish?
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
  4. banzai

    Thread Starter Member

    Jan 3, 2014
    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
  5. ericgibbs

    Senior Member

    Jan 29, 2010
    Last edited: Oct 28, 2014
  6. crutschow


    Mar 14, 2008
    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.