THERMORESISTORS
SUPPLY OF THERMISTORS FOR EVERY APPLICATION
Resistance Temperature Detectors (RTDs) are precise and reliable temperature sensors widely used in various industrial and civilian sectors.
There are different types of RTDs, which, depending on their coating and resistance in Ohms, will have characteristics suitable for specific uses and sectors. Similar to thermocouples, RTDs are more reliable and stable, measuring temperatures up to 850°C.
THE ADVANTAGES
- Wide range of nickel and platinum resistance temperature detectors (RTDs) for various applications
- Precise and consistent temperature measurement
- Available in bulk quantities
HOW DO RESISTANCE TEMPERATURE DETECTORS (RTDS) WORK?
The operation of thermoresistors is based on the linear relationship between temperature and electrical resistance levels of a metal. By powering the thermoresistor with a constant current and measuring the variation in the metal's electrical resistance levels, it is possible to determine the temperature to which the thermoresistor is exposed.
The most commonly used metals are Platinum and Nickel, which have high specific electrical resistance and are highly stable, allowing for precise measurement over a wide temperature range.
The maximum temperature detectable by thermoresistors reaches 850 degrees Celsius, and the measurement range covers temperatures from -200/+850 degrees Celsius with high measurement precision.
WHAT TO CHOOSE BETWEEN THERMORESISTORS AND THERMOCOUPLES
Thermocouples and thermoresistors are both sensors used to measure the temperature of materials. Primarily used in the industrial sector, these two instruments have specific characteristics that make them suitable for different production applications.
Thermoresistors provide very precise measurements and are easy to calibrate, but they have a limited measurement range, reaching up to a maximum of 850°C.
Thermocouples
measure temperature with less precision but have a measurement range that extends up to 2000°C. The choice between thermoresistors and thermocouples depends on measurement needs, the required precision, and the necessary temperature range.
ADVANTAGES AND DISADVANTAGES OF THERMORESISTORS
Thermoresistors are among the most commonly used probes for precise and reliable temperature measurement, both in civil and industrial contexts.
Here are the pros and cons of using thermoresistors.
ADVANTAGES
Advantages of resistance thermometers:
- good accuracy;
- stable measurements (repeatable readings over time);
- easy to calibrate.
DISADVANTAGES
- high cost;
- renge of measured temperatures more limited;
- do not measure temperatures above 1000°.
TYPES OF THERMORESISTORS
The main way to distinguish between different types of thermoresistors is by their resistance value in ohms, measured at a temperature of 0°C. Among thermoresistors, the most common are the Pt100 and Pt1000, which are platinum sensors with resistances of 100 or 1000 Ω.
PT100 THERMORESISTORS
PT100 thermoresistors are certainly among the most widely used in various fields of application. PT100s are platinum (Pt) probes characterised by high accuracy in measuring temperature and resistance to external agents. ESAF Srl offers PT100 models with mineral insulation or traditional insulation to meet the different needs of production processes.
PT1000 THERMORESISTORS
Very similar to Pt100 thermoresistors, this model is more suitable when a longer cable is present. In fact, the higher resistance of this probe allows for compensation of measurement inaccuracies caused by a longer cable.
MATERIALS USED FOR RESISTANCE: PT AND NI
In thermoresistors, the most widely used metals are platinum and nickel, materials with high resistivity and stability, which allow for the creation of precise and small probes. Depending on the type of metal used, the thermoresistor is classified as Pt (Platinum) or Ni (Nickel).
PLATINUM THERMORESISTORS PT
Platinum resistance thermometers have a measurement range between -200 and +850°C. They are characterised by high resistance to oxidation and excellent stability.
NICKEL THERMORESISTORS NI
Nickel thermoresistors have a more limited use compared to platinum ones, due to the reduced ability of nickel to resist oxidation, which limits its measurable temperature range to -100/+200°C.
THERMORESISTORS:
TOLERANCE CLASSES
In addition to the metal used for the probe, the measurement accuracy in thermoresistors varies significantly depending on the type of connection used between the probe and a transmitter.
The most commonly used connections are two-wire, three-wire, and four-wire configurations.
Here are the differences based on the type of connection:
- Two-Wire Connection: This is the type of connection for thermoresistors that provides the least accurate measurements. Particularly in cases where the distance between the probe and the transmitter is large, the resistance levels of the metal may yield imprecise measurements. This type of connection is suitable for applications with short cables or where high precision is not required.
- Three-Wire Connection: This method is widely used in industrial sectors due to its high level of precision. The third wire allows for compensation of the resistance of the connection cable, providing a more accurate representation of the resistance variation within the probe and, consequently, the temperature measurement.
- Four-Wire Connection: This is the method that provides the most reliable measurements. The four wires compensate for almost all error margins due to the resistance of the connection cable. In class A thermoresistors with a four-wire connection, the error margin is reduced to just 0.45°C.
USES OF THERMOCOUPLES
The use of thermocouples as temperature sensors is widespread, both in industrial and domestic contexts and applications.
THERMOCOUPLES FOR BOILERS, OVENS, AND HOBS
In domestic settings, thermocouples are widely used for heating and the operation of hobs and ovens. In these contexts, the thermocouple functions as a temperature-regulating thermometer, sending an electrical signal that controls the opening or closing of the gas valve.
The thermocouple acts as a safety device for gas ovens and hobs, indicating the closure of the gas valve if the flame goes out. In this way, once the thermocouple detects a temperature drop due to the absence of a flame, it sends an electrical signal to stop the gas flow.
INDUSTRIAL THERMOCOUPLE PROBES
For measuring high temperatures or under challenging conditions, thermocouples are a crucial tool within industrial probes used in production processes. The significant advantage of thermocouples in these situations is their durability, which allows them to be used in a wide range of industrial contexts.
THERMOCOUPLES OR THERMORESISTORS: THE DIFFERENCES
Thermocouples and thermoresistors are among the most commonly used probes for temperature measurement, both in industrial and civil sectors.
When choosing which of these electrical components to use, it is essential to consider two factors: precision and the type of temperatures to be measured. Thermocouples are less precise than thermoresistors, but they are easier to calibrate and more durable.
If the measurement requires very high temperatures, above 650°C, thermocouples are the ideal measurement tool due to their wider measurement range.
