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Frequently Asked Questions

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Revision: 16-Apr-15

Document Number: 29111

For technical questions, contact: nlr@vishay.com

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000

FAQ on Temperature Sensing and NTC Thermistors

WHY SHOULD I USE A NTC THERMISTOR AS A TEMPERATURE SENSOR INSTEAD OF ANY OTHER

TYPE OF CONTACT TEMPERATURE SENSOR?

• NTC thermistors provide the highest available degree of sensitivity to temperature changes. NTC thermistors have a

temperature coefficient of - 3 %/°C to - 5 %/°C, compared to just 0.7 %/°C for a silicon-based sensor, 0.385 %/°C for a

platinum-based sensor, and 0.3 %/°C to 0.55 %/°C for a nickel-based sensor.

• NTC resistance values can be high to very high, which means that low-current, two-point measurements can be done with a

high level of precision.

• NTC thermistors offer the best performance/price ratio of the available temperature sensors.

• NTC thermistors can be supplied in a variety of different packages. Options include surface-mount (SMD) and through-hole

(leaded) versions and assembly probes for fluid, gas, or contact surface temperature measurement.

IS THE NON-LINEARITY OF A NTC THERMISTOR A PROBLEM FOR PROPER USE?

• For the temperature detection of one or several threshold values, the non-linearity does not play a role in the accurate

measurement.

• For proper temperature evaluation based on a measured resistance value, the resistance versus temperature relation can be

stored in the form of a look-up table with easy interpolation, or as an algorithm which can be programmed to give an exact

matching temperature based on a resistance value.

• All the R-T curves of the Vishay NTC thermistors are available on the Vishay web site as downloadable files, for easy

calculation of values and limits.

www.vishay.com/resistors-non-linear/curve-computation-list/

and www.vishay.com/resistors-non-linear/ntc-curve-list/

I NEED A LINEAR VOLTAGE DEPENDANCE IN FUNCTION OF THE TEMPERATURE.

• By combining several NTC thermistors (3 or even 4) with fixed resistors in one network, it’s often possible to generate such

linearity with a sensitivity of for example 20 mV/°C on a temperature range from -50 °C to 150 °C.

Just send your request to edesign.ntc@vishay.com.

I WANT TO BUILD A VOLTAGE DIVIDER PROVIDING A THERMAL VOLTAGE VARIATION FROM

X TO Y VOLTS OVER A TEMPERATUR RANGE: CAN YOU GIVE ME THE REFERENCES OF THE

THERMISTOR AND OF THE FIXED RESISTORS NEEDED TO ACHIEVE MY GOAL?

• Vishay provides a web tool which performs such computation.

Just go to www.vishay.com/resistors-non-linear/resistor-thermistor-netsim/

I NEED A NTC THERMISTOR MATCHING SEVERAL TEMPERATURE/RESISTANCE POINTS, WITH

VALUES AND TOLERANCES GIVEN. HOW DO I OBTAIN SUCH A DEVICE?

• Point-matched or curve-tracked interchangeable NTC thermistors are usually installed in automotive applications.

• Please send your requirements directly to your Vishay office or to nlr@vishay.com

. A proposal will be made based on types

that optimally match your request.

• Please provide as much detail as possible about the application, including temperature range, type of medium, accuracy

needed, reaction time, mounting considerations, etc.

• We propose as well a program for design-in of NTC thermistors which can guide you to the right product selection. You can

look to a video presentation of how this software operates:

www.vishay.com/videos/resistors/edesign-demonstration-for-ntc-thermistors

.

This software can be obtained by emailing to edesign.ntc@vishay.com

CAN I USE A STANDARD THERMISTOR FROM THE AVAILABLE RANGES, OR DO I NEED SPECIAL

DEVICE TYPE?

• Our standard series types withstand standard conditions of use (95 % relative humidity at 40 °C) and are not insulated. If there

is any possibility of the components coming in contact with conductive surfaces having different potentials, leakage currents

can result, deteriorating the measured resistance value. If the component must be insulated, please contact your Vishay

representative or use insulated parts from the NTCLE300, NTCLE301, NTCLE201 series.

WHERE CAN I FIND AN OVERVIEW OF THE R-T TABLES OF THE VISHAY NTC THERMISTORS?

• Look on the Vishay website under R/T computation files at www.vishay.com/resistors-non-linear/curve-computation-list/ and

www.vishay.com/resistors-non-linear/ntc-curve-list/

Summary of content (3 pages)

PAGE 1
Frequently Asked Questions www.vishay.com Vishay FAQ on Temperature Sensing and NTC Thermistors WHY SHOULD I USE A NTC THERMISTOR AS A TEMPERATURE SENSOR INSTEAD OF ANY OTHER TYPE OF CONTACT TEMPERATURE SENSOR? • NTC thermistors provide the highest available degree of sensitivity to temperature changes. NTC thermistors have a temperature coefficient of - 3 %/°C to - 5 %/°C, compared to just 0.7 %/°C for a silicon-based sensor, 0.385 %/°C for a platinum-based sensor, and 0.3 %/°C to 0.
PAGE 2
Frequently Asked Questions www.vishay.com Vishay I WANT TO OBTAIN A SPREADSHEET OF THE RESISTANCE TEMPERATURE DEPENDENCY OF MY VISHAY NTC THERMISTOR REFERENCE. • Just go to “My VISHAY NTC curve” (www.vishay.com/resistors-non-linear/ntc-curve-list/), download the file, open the file following the instructions, indicate your P/N, temperature range and step and all R/T data of the requested part will be showed.
PAGE 3
Frequently Asked Questions www.vishay.com Vishay ARE THERE SURFACE-MOUNT EQUIVALENTS FOR ALL THROUGH-HOLE (LEADED) THERMISTORS? • Not for all the R25 values. Vishay offers equivalents for standard R25 values (10K, 100K with B25/85 = 3435K and 3977K). Consult the R/T computation programs for the SMD series and choose the low, medium, or high B-values. The program will give you the appropriate part number.