PT100 Sensors: What are they, and which types are best for your needs?

This is your guide to PT100 sensors, covering applications, accuracy classes, circuit types, and El-Watch products. Find the best solution for your temperature measurement needs.

Are you wondering what PT100 sensors are and how they can help you monitor and control temperatures in various processes and environments? Then, you’ve come to the right place! This article covers everything about PT100 sensors, their functions, applications, and El-Watch’s innovative wireless solutions.

Relevant article: El-Watch wireless sensors: User-friendly IoT monitoring is here!

Read on and learn how to optimize your temperature measurements with El-Watch’s groundbreaking Neuron series. Let’s find out why PT100 sensors are so popular and how El-Watch’s products can revolutionize your temperature monitoring!


  1. What are PT100 sensors?
  2. Application areas for PT100 sensors
  3. How is the signal converted to temperature?
  4. Typical circuit types for conversion
  5. PT100 sensor accuracy classes
  6. Typical types of PT100 sensors
  7. El-Watch Neuron – Wireless PT100 variants
  8. El-Watch product range
  9. Takeaway
  10. FAQ

What are PT100 sensors?

PT100 sensors are a type of temperature sensor based on resistive temperature detectors (RTD). These sensors work by having a very thin platinum wire that changes resistance proportionally with temperature changes. At 0°C, PT100 sensors have a resistance of 100Ω, which increases as the temperature rises and decreases as the temperature falls.

Two types of PT100 sensors


This is the original type of PT100, where a thin platinum wire is wound around a glass or ceramic base and then covered with an insulating material, e.g., aluminum oxide. This type has the highest accuracy and the largest temperature range but is relatively large and expensive compared to thin film.

Thin film

This type of PT100 sensor has platinum printed on a ceramic base covered with glass. This results in lower production costs, better vibration resistance, faster thermal response, and better sensitivity. The downside is that the sensor has a smaller temperature range before giving a non-linear response, especially at low temperatures (below -50°C).

Application areas for PT100 sensors

PT100 sensors are employed across numerous industrial and commercial applications, such as process control, furnaces, and refrigeration systems. Their high accuracy, long-term stability, and capacity up to approximately 600°C make them a favored option for a wide range of temperature measurements.

How is the signal converted to temperature?

You must first transform the resistance value into an electrical signal before you can convert the signal from a PT100 sensor to a temperature. This is usually done by passing a precisely measured current through the sensor while measuring the voltage drop across it.

An AD converter digitizes the voltage and converts it into a temperature measurement. Typically, one would employ a formula based on the Callendar-Van Dusen equation for this task. This formula takes into account the resistance at 0 degrees Celsius and the temperature coefficient specific to platinum (0.385Ω/°C).

You can also use a conversion table

A conversion table can be used to quickly and easily determine the temperature based on measured resistance. The table will display resistance versus temperature in steps, allowing the user to easily read the temperature.

There are also digital converters and software that can perform this conversion automatically. In this case, you would, for example, read the resistance in the PT100 element using an Ohm meter and look up the corresponding temperature in a conversion table. For instance, 138.5Ω corresponds to a temperature of 100°C.

Here’s an example of a simplified PT100 conversion table. Note that a complete table will have more data points for higher accuracy.

Resistance (Ω)Temperature (°C)

To use this table, measure the resistance with an Ohm meter and find the closest value in the table. The estimated temperature measured by the PT100 sensor is the temperature corresponding to this resistance.

Keep in mind that this is a simplified table. A more detailed table will provide better accuracy. You can also use linear interpolation between two nearby values to better estimate if the resistance you measure is not exactly equal to any of the values in the table.

Typical circuit types for conversion

2-wire circuits

2-wire circuits are the simplest and most basic type of circuit for PT100 sensors. In this configuration, there are two wires connecting the sensor to the measuring instrument. The disadvantage of this circuit type is that wire resistance can affect the measurement and reduce accuracy unless compensated for through calibration.

Wireless sensors usually employ 2-wire circuits, which function optimally without any signal degradation. Wireless sensors achieve increased accuracy by wirelessly digitizing and transmitting the signal from the electronics, which are in close proximity to the sensor wires. Essentially, the digitized signal serves as an identical reproduction of the measurement.

Example of a conversion circuit

Drawing of a PT100 circuit.

3-wire circuits

3-wire circuits improve on 2-wire circuits and are used to reduce errors caused by wire resistance. In this circuit type, a third wire measure and compensate for any resistance errors, providing better accuracy.

4-wire circuits

4-wire circuits provide the best accuracy for PT100 sensors. In this configuration, four wires measure and compensate for wire resistance. This ensures that the measurements are as accurate as possible, regardless of wire length and quality.

PT100 sensor accuracy classes

PT100 sensors come in different accuracy classes, which determine the sensor’s accuracy in relation to a reference value. The most common accuracy classes are Class A and Class B. Class A sensors are more accurate than Class B sensors, but they are also generally more expensive.

Other important specifications

Some other important specifications to consider when choosing a PT100 sensor include the temperature range, sensitivity, response time, and environmental conditions that sensors must withstand, such as vibration, corrosion, and pressure.

Typical types of PT100 sensors

Surface-mounted sensors

The surface-mounted sensors are designed to measure the temperature on an object’s surface, like a pipe or tank. You can attach these sensors directly to the surface using adhesive, welding, or mechanical fasteners.

Screw-in sensors

Screw-in sensors are designed to measure the temperature inside an object, such as a liquid or pipe. Screwing the sensor into the object to be measured through a threaded connection enables direct contact with the medium to be measured.

Probe sensors

Probe sensors are mounted in a protective sheath, often made of stainless steel or ceramic. This sheath protects the sensor from external influences, such as impacts and corrosion, and provides better stability and accuracy.

El-Watch Neuron – Wireless PT100 Variants

Advantages of wireless sensors

Wireless PT100 sensors offer a range of advantages compared to wired sensors. They are easier to install and maintain, and they reduce the need for complex wiring networks and cable penetrations. Wireless sensors also provide greater flexibility in placement and can be easily moved as needed.

Unique features of the El-Watch Neuron series

The El-Watch Neuron series of wireless PT100 sensors offer a range of unique features that make them ideal for various applications. These include:

  • Long range: The Neuron series uses advanced wireless communication to ensure a reliable connection, even over large distances.
  • Easy installation: Thanks to their wireless design, Neuron sensors are easy to install and require minimal time and tools.
  • Battery-powered: The battery-powered Neuron sensors do not require an external power supply and operate independently of other systems.
  • Robust design: The sensors in the Neuron series are designed to withstand harsh environmental conditions, including high temperature, humidity, and vibration.

Product brochure

Find the perfect sensor solution

We offer over 50 different sensor types. Explore the possibilities in our product brochure.

El-Watch product range

El-Watch offers a wide range of PT100 sensors suitable for various applications and environments. Their Neuron series is specifically designed for wireless communication and easy installation.

Neuron PT100 25 cm Probe

This sensor is equipped with a 25 cm long probe, making it suitable for measuring temperature in deep containers or inaccessible locations. It also has a high-temperature tolerance and is ideal for use in furnaces and other heat sources.

Neuron PT100 25 cm Probe – Product details

Neuron PT100 Bolt M6

The Neuron PT100 Bolt M6 is a sturdy, compact sensor perfect for taking temperature measurements of machines and engines. Its simple installation involves screwing the sensor directly into an M6 thread, offering precise readings without significantly affecting the equipment.

Neuron PT100 Bolt M6 – Product details

Neuron PT100 Process Connection

This sensor is designed for seamless integration with process control systems and pipelines. Its standard process connection ensures effortless installation and excellent compatibility with current equipment.

Neuron PT100 Process Connection – Product details


PT100 Process Connection

The PT100 Process Connection sensor comes ready to use out of the box and are fitted with a 6x100mm sensor element and 1 meter cable between electronics and sensor. 

Neuron PT100 Ring Lug

The Ring Lug is a surface-mounted sensor ideal for measuring the temperature of pipes, tanks, and other flat surfaces. It is easy to install using a ring clamp and provides accurate measurements without the need for direct contact with the medium.

Neuron PT100 Ring Lug – Product details

Neuron PT100 Surface Patch

This sensor is designed for easy mounting on flat surfaces using a self-adhesive patch. It is ideal for temperature measurement in locations where it is difficult or impractical to install other types of sensors, providing reliable and accurate measurements.

Neuron PT100 Surface Patch – Product details

Neuron PT100 High Temperature

The Neuron PT100 High-Temperature sensor is specifically designed for use in high-temperature applications, such as furnaces, combustion chambers, and exhaust systems. It can withstand temperatures up to 600 degrees Celsius and provides accurate and stable measurements even under extreme conditions.

Neuron PT100 High Temperature – Product details


Neuron PT100 / Neuron PT100 High Temperature

The Neuron PT100 is designed to be connected to a PT100-element and will transfer the measured temperature to the Neuron Cloud.


El-Watch offers a comprehensive range of PT100 sensors suitable for a wide variety of applications and environments. Their Neuron wireless sensor series provides reliable and accurate temperature measurements with minimal installation and maintenance. Visit El-Watch’s product pages to find the perfect sensor for your needs.

Related article: What is predictive maintenance? (Definition, examples, IoT solutions)

Ready to try wireless sensors?

Please contact our Sales Manager for some good advice and a nice sensor- chat.


What is the main difference between Class A and Class B PT100 sensors?

Class A sensors have higher accuracy than Class B sensors, but they may also be more expensive. The choice of accuracy class depends on your specific temperature measurement needs and budget.

Can PT100 sensors be used in humid environments?

Yes, you can use PT100 sensors in humid environments, provided that you make sure to protect the sensors with suitable housing and ensure they have adequate sealing to prevent moisture intrusion.

What is the range of wireless Neuron sensors from El-Watch?

The range of wireless Neuron sensors depends on several factors, including antenna type, radio wave conditions, and any obstacles in the signal path. Generally, the Neuron series offers long-range and reliable wireless communication in most applications.

How long do the batteries in Neuron sensors last?

The battery life of Neuron sensors depends on the usage pattern and communication frequency. However, the batteries are generally designed to last up to 10 years under normal operating conditions.

How can I determine which type of sensor is best for my application?

To choose the right sensor for your application, consider factors such as temperature range, accuracy requirements, environmental conditions, and mounting method.

Other useful articles How to Select and Design the Best RTD Temperature Sensing System

Digital Journal: Process Parameters Releases Specs of Pt100 Platinum Resistance Thermometers

Realpairs: Pt100 Sensor Explained | Working Principles

Sensors 2023: Approach to Connecting Pt100 by Utilizing an Electroacoustic Resonance Tube


Further reading