What are the Uses and Types of RTDs?
Resistant Temperature Detector (RTD) is a type of temperature sensor, often referred to as resistance thermometers. Its works on the basis of change in resistance of metal due to change in temperature.
RTD is used in a variety of applications and is preferred over other types of temperature sensors for its accuracy, ease of use, repeatability, and cost. Temperature sensors are used across different domestic and industrial applications.
Resistance thermometers are most commonly used for temperature measurement from -200C to 600C, some sensors are designed to operate as high as 1000 C. Resistant Temperature Detectors are available with a variety of resistance element materials.
Two Most Widely Used Sensor Types Are:
1. Wire-wound RTD
This type of RTD has a small diameter wire, most commonly of platinum that is wound in a coil placed inside a ceramic/glass insulator.
Extension wires are welded to this platinum coil that extend outside the insulator body.
This type of sensor is longer in length and are more delicate compared to Thin Film. Wire wound RTD have good accuracy over wider temperature range.
2. Thin-film RTD elements
Thin film elements are made by depositing a very thin layer of resistive platinum metal on a ceramic base. This film is then coated with an epoxy or glass that helps protect the deposited film and also acts as a strain relief for the external lead wires.
This type of RTD perform better in vibration application and for spot temperature measurement. Thin film sensors are most widely used sensor type due to its versatility and cost effectiveness.
RTD can also be differentiated based on the resistance element material. They are commonly referred to as Pt100, P1000, Ni120, Cu100 etc.
Here the letters denote the material of element and the numbers indicate the resistance value at zero degrees C. So, a Pt100 element has Platinum resistance element that has a resistance of 100 Ω at 0°C and a Ni120 has Nickel element with resistance of 120 Ω at 0°C.
Each material element has its own advantage and limitations.
Platinum elements are most widely used, it has excellent resistance to corrosion, long term stability and a wider temperature range from -200 °C to 1000 °C. However, platinum being Nobel metal these sensors are more expensive compared to others.
Nickel elements are less expensive compared to Platinum elements, they have higher resistance at 0 °C and are offer higher sensitivity due to high resistance ratio. However, the have limited temperature range of -80°C to 260°C and the age quicker.
Copper elements have excellent resistance to temperature linearity compared to the other elements and is a low-cost material. However, it is less resistant to corrosion and its use is limited to temperature range of -200°C to 260°C.
Wide choice of sensor type, element materials and configurations can sometimes be intimidating for you to select the right product, our team of experts are always at your disposal to help you chose the right product for your measurement needs. For more info, Get in touch with us!