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Thermistor sensor
Last Post 20 Nov 2012 07:24 AM by georgeamad. 3 Replies.
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NemOreo
New Member
New Member
Posts:2

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30 Jul 2012 07:50 AM
    I'm trying to use a thermistor (2553 ohms at 25 C) sensor to measure temperature. The ultimate goal is to measure temperature with great accuracy. I have set up a voltage divider circuit and calculated the resistance of my thermistor for various temperatures. With the equation: E1=E2(r2/(r1+r2)), r2 is thermistor. And then graphed the data and created an equation to predict unknown temperatures. This doesn't work because everytime I collect data points, I'm calculating a different resistance for the known temperature. Can anyone provide thoughts on collecting more meaningful data, or another way to get accurate data?
    NemOreo
    New Member
    New Member
    Posts:2

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    30 Jul 2012 07:56 AM
    Also I've swapped out the power supply for a function generator (using 5 V), multimeter for oscilloscope, and I have 2 thermistors purchased from Omega.
    Nathaniel
    Basic Member
    Basic Member
    Posts:193

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    30 Jul 2012 02:02 PM
    Are you trying to achieve better accuracy than what the thermistors are rated for by Omega?

    If you are then you need test and verify your test against known standards. This can not simply be done with calculations.

    How stable was your power supply?

    How accurate was your multimeter?

    Is your function generator more stable than the power supply outputting a steady DC voltage? This will be critical in achieving high accuracy.

    Is your oscilloscope more accurate than your multimeter?

    Niel Leon
    engineering.com
    georgeamad
    New Member
    New Member
    Posts:4

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    20 Nov 2012 07:24 AM
    Sounds like a unstable connection or power supply.

    check all connections
    monitor the power supply voltage as well as the voltage divider voltage with the scope
    is your measurement equipment floating? best connect everything to the same ground potential

    if you want to determine the temp accurately, better use the steinhart equation:
    http://www.resistorguide.com/ntc-thermistor/
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