Thermistor circuit design based on reference sloa052 and sboa097

David Zhang16358

Other Parts Discussed in Thread: REF200, LM335, INA330

I have designed my NTC Thermistor circuit based on reference sloa052 and sboa097.

But the input temperature range is from -40C to +150C instead of from 0C to +100C.

When input temperature is -40C, the resistance of Thermistor is 191908 ohm, which means the input voltage will be +20V if I use REF200.

I have selected Circuit 2: Single-Supply/Single-Part Approach in sboa097 to reduce the input voltage down to +3.3V ADC interface.

Please send me any suggestions if my idea is practical.

Many thanks.

over 12 years ago

0 Chris Featherstone over 12 years ago

TI__Mastermind 23190 points

David,

We are currently looking into this and will get back to you shortly.

0 Aaron Heng over 12 years ago in reply to Chris Featherstone

TI__Mastermind 32130 points

Hi David,

I would suggest you to use our LM335 Precision Temperature Sensors. This device operates from -40°C to 100°C. If you use the LM335, it will get rid of a lot of your circuitry. Please let me know if you are interested, and we can take this offline.

Aaron Heng

0 Bruce Trump over 12 years ago in reply to Aaron Heng

Guru 21975 points

David,

Aaron has provided a good alternative to your thermistor circuit. Thermistors tend to be more nonlinear over your wide temperature range. A semiconductor sensor may be a better solution. Another alternative would be an RTD sensor which is far more linear than a thermistor.

Regards, Bruce.

0 David Zhang16358 over 12 years ago in reply to Bruce Trump

Expert 1860 points

I know the solution you gave to me is a good one.

But the customer want to use the 10K NTC in attached file.

Do you have any ideas regarding to 10K NTC?

Many thanks.7725.Tasseron_TSD_2.pdf

0 Collin Wells over 12 years ago in reply to David Zhang16358

TI__Guru 62915 points

Hi David,

For an easy to use analog solution, please consider the INA330. It is optimized for 10kOhm NTC thermistor applications.

www.ti.com/lit/ds/symlink/ina330.pdf

Regards,

Collin Wells
Precision Linear Applications

0 David Zhang16358 over 12 years ago in reply to Collin Wells

Expert 1860 points

Can INA330 can fit -40C to +150C range?

Have nice weekend.

David.

0 Bruce Trump over 12 years ago in reply to David Zhang16358

Guru 21975 points

David,

The INA330 is really intended as a set-point temperature controller. It does not provide any real advantage for wide range temperature measurement with a thermistor.

A simple way to improve the nonlinearity of a thermistor with current excitation is with a parallel resistor. The same result is achieved with voltage excitation and a series resistor. I've attached three Powerpoint slides to show this point. See the attached file. A 5k resistor seems to work reasonably well for this temperature range.

Regards, Bruce.

8360.Thermistor Linearization.pdf

0 David Zhang16358 over 12 years ago in reply to Bruce Trump

Expert 1860 points

Hi Bruce,

I will use your suggestions.

Many thanks to all people gave me the sincere helps.

David.

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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Thermistor circuit design based on reference sloa052 and sboa097