Thermistor relationship, linearizing (really easy)

In summary, the conversation is about using a thermistor as a temperature sensor for coursework. The person is struggling with obtaining accurate readings and understanding how to linearize the results. They are also unsure about the appropriate range of resistances they should be getting and how to plot a voltage-temperature graph. Additionally, they mention the possibility of using a logarithmic plot.
  • #1
gRACK
2
0
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.
 
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  • #2
What are your units of temperature? Thermistors vary quite a lot I suspect. Could you post the links to the data sheets?
 
  • #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.
 

Related to Thermistor relationship, linearizing (really easy)

What is the thermistor relationship?

The thermistor relationship refers to the inverse relationship between the resistance of a thermistor and its temperature. As the temperature increases, the resistance of the thermistor decreases, and vice versa.

How can I linearize a thermistor?

To linearize a thermistor, you can use the Steinhart-Hart equation, which is a mathematical model that relates the resistance of the thermistor to its temperature. This equation can be used to convert the non-linear relationship of a thermistor into a linear one.

Why is linearizing a thermistor important?

Linearizing a thermistor is important because it allows for more accurate temperature measurements. The non-linear relationship between resistance and temperature can make it difficult to accurately determine the temperature using a thermistor, but linearizing it can help to overcome this issue.

What types of thermistors can be linearized?

There are two main types of thermistors that can be linearized: NTC (negative temperature coefficient) and PTC (positive temperature coefficient) thermistors. Both types can be linearized using the Steinhart-Hart equation.

Are there any limitations to linearizing a thermistor?

Yes, there are some limitations to linearizing a thermistor. The Steinhart-Hart equation is not accurate for extreme temperature ranges and may require adjustments for different types of thermistors. Additionally, the accuracy of the linearized thermistor may also depend on the quality and precision of the components used in the circuit.

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