Difference Between RTD & Thermistor

Hello, friends, I hope you all are doing great. In today’s tutorial, we will discuss the Difference Between RTD & Thermistor. Both of these thermistors and RTD are used to find the value of temperature. But the basic difference between them is that RTD is constructed with metallic material and the thermistor is constructed with semiconductor material. Due to construction with the semiconductor materials, there are 2 temperature coefficients of thermistors positive and negative. But most thermistor has a negative temperature coefficient their resistance value reduces with the increment in temperature.

. The RTD is used to find a large value of temperature. In today’s post, we will have a detailed look at both RTD and thermistors with the details and compare them to find their differences. So let’s get started with the Difference Between RTD & Thermistor.

Difference Between RTD & Thermistor

RTD

• The instrument used to find the temperature variation is called RTD or also called the resistance temperature detector.
• It is constructed with metallic substances such as platinum, nickel, copper, etc.

• Its accuracy is less than the thermistor.
• It is an expensive device.
• It provides high resistivity.
• The physical dimensions of this device are larger than the thermistor.
• It is used in different industries to find the temperature of machines.
• Its hysteresis effect is less.
• Its time response is less than the thermistor.
• Its measurable temperature range is -230 centigrade to 660 centigrade.
• Its characteristic curve is linear.
• It is a less sensitive material.
• It operates on different types of curvature and tolerance values normal operation curve for this device is DIN.
• The type of RTD is UPRT which offers a high value of accuracy.

RTD Types

• 2 basic types of RTD are normally employed thin-film coils and the third one is wire.
• The above types are generally used at the industrial level some other types are used for measurement of less temperature than higher temperature devices that are used in industries.

Carbon resistor RTD

• These modules are less expensive and generally used for less-value temperature measurement. There is no effect of strain and hysteresis forces on devices

Strain-free RTD

• These devices are used to measure temperature values close to 961 centigrade. There is a platinum-crated coil wounded on it and they can easily change their state according to temperature change to show temperate values.

Thin-film RTD

• In this device temperatures, a measurement module is created through the use of platinum or plated ceramic substance.
• The thickness of the platinum material layer is almost one to ten nanometers. To save this layer from the outer environment is coat of glass exists on it

Thermistor

• It is a heat-sensitive device whose resistance value varies with the temperature change.
• It is manufactured with semiconductor materials.
• It provides high accuracy. So we can measure a small change in temperature due to the negative temperature coefficient.
• It provides fast response time.
• It is a less expensive material.
• A thermistor is a combination of thermal and resistor.
• Its practical applicaton are inrrcu currnet handler as tempratuer mesurig device.
• It has two temperature coefficients first one is positive and the second one negative
• Its resistivity is less than the RTD.

• Its hysteresis effect is large.
• Its graphical representation is nonlinear.
• Its sensitivity is larger than the RTD.
• Its physical size is less than the RTD.
• It is used to find the temperature of devices used in a home.
• Its measured temperature range is -60 to 15 centigrade.
• It has two types NTC and PTC NTC resistance drops with temperature rise and PTC resistance rises with temperature rise.
• PTC is used to control overcurrent and is used in series combinations.

RTDs and NTC thermistors

Range:

• The thermistor is used for monitoring small-range temperatures and some RTDs can measure 600 centigrade, thermistors have features to measure 130°C.
• For applications where a temperature of more than 130 degrees is involved use an RTD probe.

Cost:

• Thermistors are lower cost than RTDs. If the application temperature is according to a given range, thermistors are best to use
• Thermistors with different temperature ranges have higher costs than  RTDs.

Sensitivity:

• Thermistors and RTD work for temperature variations with changes in resistance value. But thermistors vary resistance through 10 times of ohm per degree, then a smaller number of ohms for RTDs sensors. With the use of the correct meter, users can get accurate readings.
• Thermistors’ response time is higher than RTDs which makes variation in temperature easily. The sensing part of the thermistor is small like a pin head and provides high-speed feedback.

Accuracy:

• Best RTDs come with the same accuracies as thermistors, RTDs provide resistance in the system. The use of long cables can change values other than acceptable error levels.

Features	Thermistor	RTD
Temperature Range	-100 to 325°C	-200 to 650°C
Power required	Constant voltage or current	Constant voltage or current
Response time	0.12 to 10s	1 to 50s
Susceptibility to electrical noise	susceptible to high resistance only	Less susceptible
Cost	Low to medium	High
Accuracy	0.05 to 1.5°C	0.1 to 1°C
Long-term stability	0.2°C one year	0.05°C one year
Linearity	Exponential	linear

FAQs

That is a detailed post about the difference between RTD and Thermistor if you have any queries ask in the comments. Thanks for reading. Have a good day.