wheatstone bridge with NTC thermister

Discussion in 'General Electronics Chat' started by johnson kennady, Jun 14, 2013.

  1. johnson kennady

    Thread Starter New Member

    Jun 14, 2013

    i am using NTC thermister with wheatstone bridge for temperature measurment. i connected 5.6K resistance in three arms and connected 10K potentiometer with the NTC thermister in the fourth arm.

    i adjusted the potentiometer in order to make the bridge balanced.

    in AIR CONDITIONED room, the bridge gets unbalanced, so that i adjusted my POT to make the bridge balanced.

    similarly in NORMAL room without Air conditioned, then i adjusted POT for balancing.

    My quetion is " I dont want to adjust POT to make the balance . is it possible to connect fixed resistance parallel with the NTC thermister which is suitable for BOTH AIR CONDITIONED and WITHOUT AIR CONDITIONED?:(
  2. JDT

    Well-Known Member

    Feb 12, 2009
    Presumably the bridge balance changes because the temperature of the NTC changes.

    So by adjusting to balance by the potentiometer you could measure the temperature. You could even put a temperature scale on the potentiometer. All working as expected - is it not?

    If you put a resistor in parallel with the NTC you will reduce the sensitivity of the NTC sensor. Replace the NTC with a fixed resistor then the system will be no longer temperature sensitive. But what's the point?

    Am I missing something?
  3. Gibson486


    Jul 20, 2012
    I am confused....it is supposed to work that way...When you change temp, the value of the thermistor changes, this it will make your bridge unbalanced so it can out out the correct voltage.

    It sounds like you do not want a bridge at all and maybe you simply want a thermistor and resistor divider.
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    Can you post your circuit?