Temperature sensor PT100 It is one of the most widely used temperature measuring devices in industry. Surely, in some industrial or technical context, you have come across this term and wondered what it does, how it works and what makes it so special.
In this article, we are going to answer all those questions, breaking down its operation, features, advantages and some installation details that you should know. While it sounds like a specific technical device, its importance cannot be underestimated, as it is key in applications where precision and reliability in temperature measurement are critical.
What is a PT100 sensor and its working principle?
El PT100 sensor It is a resistance sensor, meaning that it measures temperature based on changes in electrical resistance. The number '100' in its name indicates that it has a resistance of 100 ohms at a temperature of 0 °C. It works by using a resistive element. Platinum, since platinum has a stable relationship between temperature and resistance. This makes it ideal for accurately measuring temperatures.
The basic operating principle of the PT100 is as follows: when the temperature changes, the resistance of the sensor also changes. This resistance change can be accurately measured and correlated to an exact temperature.
Relationship between temperature and resistance
Los PT100 sensors are considered highly accurate due to the reliable relationship they have between resistance and temperature. As the temperature increases, so does the resistance of the sensor. However, it is important to mention that increasing resistance It is not completely linearThat is, it does not maintain the same proportion over all temperatures, but it remains predictable and therefore calculable.
Construction and classification of PT100 sensors
PT100 sensors vary in their constructionMost are encapsulated in a stainless steel tube or other robust material that protects them from harsh industrial environments. At one end of the sensor is the sensing element (the platinum resistor), while at the other end are the electrical connections that allow it to be installed in control or measurement systems. One thing to keep in mind is that depending on the type of construction, the sensitivity and durability of the sensors can vary significantly.
A common classification of PT100s is based on the number of wires they use for measurement:
- PT100 with two wires: This is the simplest connection method, but also the least accurate, since the resistances of the cables cannot be properly compensated.
- PT100 with three wires: The most common, it allows a good compensation of the wiring resistance if the wires have the same resistance.
- PT100 with four wires: Mainly used in laboratories as it is the most accurate method. It allows complete compensation of wiring resistance, even if the wires have different resistances.
PT100 sensor standards and accuracy
It is essential to highlight that PT100 sensors are regulated under international standards, which guarantees its consistency and precision globally. The most widely used standard is DIN IEC 60751, which defines the electrical characteristics and permissible deviations for PT100 sensors. This standard ensures that sensors have a resistance of 100 ohms at 0°C and establishes tolerance margins for different classes of sensors.
There are different accuracy classes for PT100 sensors. The highest is class AA, followed by class A and class B. Generally, the higher the accuracy class, the better the sensor's ability to give precise measurements.
Advantages of the PT100 sensor over other types of sensors
PT100 sensors offer several advantages over other temperature measuring devices, such as thermocouples. The most notable ones include:
- High accuracy: PT100s can provide accurate readings with minimal drift, which is crucial in critical industrial applications.
- Long term stability: Unlike thermocouples, which can wear out and give incorrect readings over time, PT100s maintain their accuracy longer.
- Ability to measure low temperatures: They are capable of measuring very low temperatures with great accuracy, making them ideal for industrial refrigeration applications.
- There is no gradual degradation: Instead of slowly degrading and providing incorrect data like thermocouples, PT100s typically break down completely and stop working, making fault detection easier.
Mounting and installing a PT100 sensor
Proper mounting of a PT100 sensor is just as crucial as choosing the right model. improper assembly can lead to erroneous readings, which could not only compromise the accuracy of the system, but also the safety of the entire operation.
The sensor can be mounted in a variety of ways, the most common being encapsulation in a stainless steel sheath that protects it from external elements such as moisture or dust. In some industrial systems, the PT100 sensor is mounted with a connection head to protect the electrical connections from the environment.
The location of the sensor also matters. If it is placed in a location with constant vibrations, its lifespan is likely to be shortened. drastically reducedTherefore, it is always recommended to consult with a technician before defining the final location of the sensor.
Precautions and maintenance of PT100
Like any measuring equipment, PT100 sensors require proper maintenance to ensure they function properly over their lifetime. Here are some of the most important points to keep in mind:
- Avoid installing sensors in humid environments: Moisture can cause current leakage between the wires, which will affect temperature readings.
- Corrosion Protection: In harsh industrial environments, it is crucial to protect both the sensor and the cables from corrosive materials.
- Minimize vibrations: In environments with constant vibrations, it is advisable to mount the sensor on a structure that reduces its exposure to shocks and jolts.
Types of PT100 sensors
There are several types of PT100 sensors on the market, depending on the needs of the application. The most commonly used models are:
- Industrial: Encapsulated in stainless steel sheaths, they are mainly used in industrial applications where durability is required.
- Lab: developed specifically for applications where accuracy is a priority, such as calibration laboratories.
- Thin film: These sensors are cheaper, since their platinum element is located in a thin layer on a substrate.
Temperature coefficients and the PT100 formula
The temperature coefficient of the PT100 sensor defines how its resistance changes with temperature. Generally, the most common coefficient is the 385, which means the sensor has a resistance of 138,51 ohms at 100°C.
The relationship between temperature and PT100 resistance can be calculated using the Callendar-Van Dusen formula. This formula takes into account additional factors when temperatures drop below 0°C, allowing for a very accurate calculation of temperature from the measured resistance.
Common mistakes when using the PT100
Although PT100 sensors are accurate and reliable, there are certain errors that can arise if they are not installed or used correctly. One of the most common errors is the Signal loss on long cables. After a certain length, the cables connecting the sensor to the measurement system can add additional resistance, which alters the temperature measurement. In these cases, it is recommended to use three- or four-wire connection systems to compensate for this added resistance.
Another common mistake occurs due to the moisture at the connections. As mentioned above, moisture can generate small leakage currents between the cables, resulting in incorrect readings.
Main applications of PT100
Finally, it is key to understand in which sectors these sensors are most common. PT100 They find applications in numerous industrial and scientific sectors:
- Food industries: where accuracy in temperature measurement is crucial to ensure food quality and safety.
- Medicine: Used in laboratory incubators and other medical equipment where precise temperature control is required.
- Aerospace industry: used in monitoring critical systems where accuracy and reliability are vital.
The PT100 sensor is an essential component in a wide variety of industrial and scientific sectors that require high precision in temperature measurement. Its durability, accuracy and stability make it the best choice for applications where temperature changes can have major implications.