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Measuring Fluid level using a thermistor.

  1. Apr 27, 2010 #1

    I've been writting reports on strain gauge and thermistor.

    Ive completed my strain gauge report and now i am working on my thermistor report...ive been doing some research on them and i was wondering if this is the correct information i have gathered.


    I have been asked from my lectuar to produce a report on a thermistor, but using the thermistor to measure fluid level.

    here is what i have gathered so far:

    When a thermistor is driven by a voltage source, it heats up. If submerged in a liquid, its temperature, and therefore its resistance, will remain relatively constant—as long as the liquid temperature remains relatively constant. If the liquid level drops, however, the thermistor becomes exposed, the heat dissipating effect of the liquid vanishes, the temperature rises, and—for a positive-TC element—the resistance increases.

    so if to measure the level of the fluid, if the thermistor is positioned at that level and when submerged in the liquid its resistance remains low giving out a logic 0, but if exposed then its resistance rises causing the thermistor to heat up rapidly, and from this it signals a logic 1.

    Is this correct in anwway?


  2. jcsd
  3. Apr 27, 2010 #2


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    Sounds reasonable
    Whether a high/low resistance gives a 1/0 depends on the supporting circuitry of course.
  4. Apr 27, 2010 #3
    Yep, sounds good. Just be careful that you limit the maximum current or it could go into thermal run away. We did this a few times in the lab for grins :)

    PS I think US sensors still makes NTC thermistors in metal sleeves that screw into a tank.

    - Mike
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