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Homework Help: Thermistor relationship, linearizing (really easy)

  1. Jan 31, 2008 #1
    hello,
    I'm doing coursework on using a thermistor as a temperature sensor. For my preliminary readings I had to choose between 3 different thermistors.

    Is it true that, for example, a 22k thermistor has a resistance of 22kohms at 25 degrees? (my tutor told me this) likewise, a 15k thermistor has a resistance of 15kohms at 25 degrees? My results don't show this at all; they're completely off. (eg. 6kohm resistance at 25 degrees for a 10 kohm resistor..)

    I've looked at some thermistor datasheets but i can't make head nor tail of them. could anyone give me a range of the types of resistances I should be getting, please?

    Also, anyone advice on how I should linearize my results? I understand that the resistance-temperature graph is non-linear. do I: Record the voltage at different resistances (and therefore temperatures) and plot a voltage-temp graph?

    but this won't be a straight line, am i right? so/do I have to plot a tangent to my curve?

    i'm just really unsure of what i'm doing, i've heard/read different things. Thanks in advance for any help, it is muchly appreciated.
     
  2. jcsd
  3. Jan 31, 2008 #2
    What are your units of temperature? Thermistors vary quite a lot I suspect. Could you post the links to the data sheets?
     
  4. Jan 31, 2008 #3
    A 10 kohm resistor should indeed have a resitance of 10 kohm at 25 degrees celsius.
    I found some datasheets here

    http://www.omega.com/temperature/Z/pdf/z256-257.pdf

    You are measuring the resistance with a voltage small enough to not procuce heating in the thermistor?

    You could plot the logarithm of the resistance against the temperature.
     
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