Pt100, thermocouple or NTC – choose the right temperature sensor

A temperature sensor is used to measure the temperature in, for example, a machine, an electronic component or an industrial process. But which technology should you choose? Pt100, thermocouples and NTCs measure temperature in different ways and are therefore suitable for different requirements in terms of accuracy, temperature range and response time.

This guide will help you understand the differences and choose a temperature sensor that is compatible with your temperature controller and the application in question.

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What is a temperature sensor?

A temperature sensor is a device that converts temperature into a measurable electrical signal. The signal can be used for monitoring, alarms or the automatic control of heating and cooling.

Three common types of donation are:

  • Pt100: A platinum resistance temperature sensor.
  • Thermocouple: A sensor that generates a small voltage depending on the temperature difference between the measurement point and the reference end.
  • NTC: A thermistor whose resistance decreases as the temperature rises.

Pt100 vs thermocouple vs NTC

Property Pt100 Thermocouple NTC
Measurement principle Temperature-dependent resistance in platinum. Temperature-dependent thermoelectric voltage. Temperature-dependent resistance in a thermistor.
Temperature range Wide; sensor elements are available for temperatures ranging from approximately −200 to +850 °C. The range is very wide and depends on the type; some are used at very high temperatures. Usually more limited and dependent on the model.
Accuracy Often good and reliable. It depends on the type, tolerance and measurement chain. May be very accurate within a limited range after calibration.

 

These ranges are general. The temperature limits of the finished sensor depend on the sensor element, the housing, the cable and the manufacturer’s specifications.

Pt100 sensors – for accurate and stable measurement

A Pt100 sensor is a resistive temperature sensor, also known as an RTD (Resistance Temperature Detector). The name Pt100 means that the platinum element has a nominal resistance of 100 ohms at 0 °C.

The Pt100 is a common choice when measurements need to be stable and reproducible over time. It is used, for example, in industrial process control, machinery and temperature monitoring.

A key advantage is that the change in platinum resistance is well defined. This makes the Pt100 suitable for applications where accuracy is important. Where higher standards of measurement accuracy are required, a 3- or 4-wire connection is often used to minimise the effect of cable resistance.

Choose Pt100 when: You require accurate and stable measurement across a wide temperature range and have access to a suitable measurement or control input.

Thermocouples – for high temperatures and demanding environments

A thermocouple consists of two different metallic conductors joined together at a measuring point. When there is a temperature difference between the measuring point and the reference end, a small electrical voltage is generated.

There are several types of thermocouples, such as K, J and T. They are made of different materials and have different temperature ranges and properties. Type K is commonly used in industrial applications.

Thermocouples can be a good choice at high temperatures or when a small measuring tip and a fast response are important. However, the actual response time depends on the sensor’s design and installation.

As the signal is weak, the measuring equipment must be suitable for thermocouples. The measurement also requires cold-junction compensation and the correct type of connection or compensation lead.

Choose a thermocouple when: The temperature is high, the environment is challenging, or you need a small, fast measuring point.

NTC – compact and sensitive temperature measurement

An NTC (Negative Temperature Coefficient) is a thermistor whose resistance decreases as the temperature rises. NTC sensors are often used in electronics, battery systems and other applications where a compact temperature sensor is required.

NTCs can provide high sensitivity within a limited temperature range and are often a cost-effective option. At the same time, the resistance curve is non-linear, which means that the electronics or temperature controller must be able to convert the resistance into an accurate temperature value.

When taking measurements, it is also necessary to take into account tolerances, self-heating and how the sensor is mounted in relation to the object being measured.

Choose NTC when: You need a small, sensitive sensor for electronics or for monitoring temperature within a defined range.

How to choose the right temperature sensor

Start by defining the application’s requirements. The maximum temperature is important, but the choice should also be based on how accurately and how quickly the temperature needs to be measured.

  • Temperature range: Check both the normal operating temperature and any temperature peaks.
  • Accuracy: Determine what level of measurement uncertainty is acceptable. A precise sensor does not automatically produce a precise measurement if the cabling, electronics or installation affect the result.
  • Response time: Choose a design that responds quickly enough. Protective tubes and a larger sensor mass can slow down the measurement.
  • Environment and assembly: Take into account moisture, vibrations, chemicals, pressure and how the sensor is to be mounted.
  • Connection: Ensure that the control system or temperature controller supports the correct sensor type and signal.
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Temperature sensors and temperature controllers – how they work together

Temperature sensor

The temperature sensor measures the temperature, whilst the temperature controller uses this measurement to control a process. For example, the controller can activate heating, control cooling or use PID control to maintain a desired temperature.

Temperature Sensors & Controllers

Regulator

It is important that the controller’s input is compatible with the sensor. Some controllers have universal inputs for multiple sensor types, whilst others only support, for example, Pt100 or thermocouples. Also check that the connection, measurement range and configuration are correct.

Find out more about Swelex’s temperature control solutions and controllers.

Guide to industrial sensors

Frequently asked questions about temperature sensors

  • What is the difference between a Pt100 and a thermocouple?

  • A Pt100 measures temperature by detecting changes in the resistance of platinum. A thermocouple, on the other hand, generates a small voltage that depends on the temperature difference between the measuring point and the reference end. Pt100 sensors are often used for stable and accurate measurements, whilst thermocouples are commonly used at high temperatures.

  • Is a Pt100 better than an NTC?

  • Not generally speaking. Pt100 sensors are often suitable for industrial measurement applications where high stability is required. NTC sensors may be a better option when compact size, high sensitivity and cost are important factors within a limited temperature range.

  • Which temperature sensor is the fastest?

  • This depends on the sensor’s design. Small thermocouples and NTC elements can respond very quickly, but the protection tube, sensor mass and thermal contact all affect the response time. You should therefore check the specifications of the finished sensor, not just the sensor type.

  • Can the same temperature controller be used with all sensors?

  • Some temperature controllers support several types of sensor via universal inputs, whilst others require a specific sensor. Always check the controller’s inputs and select the correct setting for Pt100, thermocouples or NTCs.

  • What does Pt100 mean?

  • ‘Pt’ stands for platinum, and ‘100’ indicates that the sensor element’s nominal resistance is 100 ohms at 0 °C.

Do you need help choosing a temperature sensor?

The right temperature sensor depends on the application as a whole – from temperature range and accuracy to installation and control. Swelex can help you find a suitable solution for temperature measurement and control.

Please contact us with details of your application, the required measurement range, environmental requirements and the temperature controller or control equipment to be used.

You can also explore heating management systems and units for a wider range of solutions in the field of cooling and temperature control.

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