# design a linear thermistor

Discussion in 'General Electronics Discussion' started by Neks4, Jan 25, 2011.

1. ### Neks4

3
0
Jan 25, 2011
Please can anyone help me with the design of a thermistor tht will give me a linear reponse...

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,412
2,780
Jan 21, 2010
Define linear.

Is a platinum RTD close enough for you? How about a K type thermocouple?

3. ### shrtrnd

3,767
487
Jan 15, 2010
*steve*'s right.
Thermistor types are typically chosen for their relative 'linearity', WITHIN a specific temperature range.
You need to know the temperature range you're looking at, and how accurate you
want the circuit to be.
Thermistors are not linear. They are chosen for their relative linearity within the characteristic
curve of it's (operating) range.

Last edited: Jan 25, 2011
4. ### Neks4

3
0
Jan 25, 2011
shrtrnd,

thank you, i know thermistors are not linear, i have a range of 20-70, i need to design a circuit, connecting ther thermistor to some component i dnt know now, to make my lnR vs 1/T(kelvin) graph linear.

what i really want to know is how to go about designing this circuit.

i willl be very grateful if u can show me how to design this circuit.. or model....

i know abt the K-type thermocouple, but i need to design it myself. thank you

Thermistor types are typically chosen for their relative 'linearity', WITHIN a specific temperature range.
You need to know the temperature range you're looking at, and how accurate you
want the circuit to be.
Thermistors are not linear. They are chosen for their relative linearity within the characteristic
curve of it's (operating) range

5. ### shrtrnd

3,767
487
Jan 15, 2010
'20 to 70' , WHAT?
The temperature matters
I'm also a little confused about whether you already HAVE a thermistor selected, or if
you're trying to design your circuit, and then select the thermistor you want.
We know YOU know what you're trying to do.
But we've only got what you tell US, about it, to work with.

6. ### Neks4

3
0
Jan 25, 2011

i got a thermistor, bt dnt know the name, it's got a lil head, and 2 pins like a scissors.. or rather a plier

7. ### shrtrnd

3,767
487
Jan 15, 2010
Alright, you've got a thermistor, you want to design a circuit for reading your thermistor. (Not design the thermistor itself).
Check www.omega.com
It's Omega Engineering, and they have good selection/application notes.
I think that'll give you a better idea which direction to take in this project.
They also have contact people for specific questions.
Good luck.