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    Hi, I'm currently conducting an experiment into electrical conductivity of several materials at high temperatures (approximately 30-200 degrees celsius) and I have got a result for copper. I am plotting resistance against temperature for each of the samples. I have a PTC thermistor and an NTC thermistor to do and a sample of Barium Titanate (BaTiO3). Now to measure the resistance for the thermistors I'm assuming I have to use a constant current as the thermistors do not obey Ohm's law. However is there any way of getting more data samples as the temperature is heating up as it takes a long time to cool down? How do I know what current to use? Thanks.
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    You should be using a constant current source for all the experiments otherwise you have no control reference.

    "However is there any way of getting more data samples as the temperature is heating up as it takes a long time to cool down?"
    What do you mean by this, as I would assume you'd take your readings as you heat the sample? If you heat the sample up and then cool repeatedly you will begin to change the structure of the sample and thus the conductivity permantly, which I don't think you want to be doing?

    Use a current that is within the current density saturation limit for all the materials, (given their size, of course). You should be able to find some typical values in data books.
 
 
 
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