RTD Sensor 3000 Series – Maltec-T MT 3001

Dpstar is one of the largest manufacturers of Temperature sensors / Thermocouple / RTD in Malaysia. We offer custom Thermocouple / RTD / Temperature Sensors that are tailored to your unique specifications. RTD’s are temperature measuring sensors that use the resistance/temperature relationship of material to measure the temperature of a body. RTDs have higher accuracy and stability as compared to Thermocouples usually in the below 600 °C range. Resistance temperature sensors are composed of realizing material generally Copper, Nickel, or platinum, which shows resistance at a specific temperature. If we want to measure temperature with high accuracy, an RTD is an ideal solution, as it has good linear characteristics over a wide range of temperatures.

What are RTD temperature sensors?

RTDs or Resistance Temperature Detectors are temperature sensors that contain a resistor that changes resistance value as its temperature changes. The most popular RTD is the Pt100. They have been used for many years to measure temperature in laboratory and industrial processes, and have developed a reputation for accuracy, repeatability, and stability.

Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core. The element is usually quite fragile, so it is often placed inside a sheathed probe to protect it. The RTD element is made from a pure material whose resistance at various temperatures has been documented. The material has a predictable change in resistance as the temperature changes; it is this predictable change that is used to determine temperature.

The pt100 is one of the most accurate temperature sensors. Not only does it provide good accuracy, but it also provides excellent stability and repeatability. Pt100 is also relatively immune to electrical noise and therefore well suited for temperature measurement in industrial environments, especially around motors, generators, and other high voltage equipment.

How Does an RTD Work?

An RTD consists of a resistance element and insulated copper wires. The most common number of wires is 2; however, some RTDs have 3 or 4 wires. The resistive element is the temperature sensing element of the RTD. It is usually platinum because as a material it is highly stable over time, it has a wide temperature range, it offers an almost linear relationship between temperature and resistance and it has a chemical inertness. Nickle or copper are also other popular choices of material for the resistive element.

An RTD works by using a basic principle; as the temperature of a metal increases, so does the resistance to the flow of electricity. An electrical current is passed through the sensor, the resistance element is used to measure the resistance of the current being passed through it. As the temperature of the resistance element increases the electrical resistance also increases.  The electrical resistance is measured in Ohms. The resistance value can then be converted into temperature based on the characteristics of the element. The typical response time for an RTD is between 0.5 and 5 seconds making them suitable for applications where an immediate response is not required.

What types of RTDs are available?

Resistance Temperature Detectors (RTDs) available today can generally be categorized into one of two basic types of RTDs, depending on how their temperature sensing element is constructed.

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 extends outside the insulator body. This type of sensor is longer in length and are more delicate compared to Thin Film. Wire wound RTD has good accuracy over a 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 performs better in vibration application and for spot temperature measurement. Thin-film sensors are the most widely used sensor type due to their 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.

Benefits of using RTD Temperature Sensors

RTDs are used within different industries including; automotive, white goods, marine, and industrial applications. The benefits of using RTDs over other temperature sensors are;

• Highly accurate
• Consistent
• Offer long term stability
• High repeatability
• Suitable for extreme environments
• Have a high-temperature range (depending on resistance element material)

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.

Nickel elements are less expensive compared to Platinum elements, they have higher resistance at 0 °C and are offer higher sensitivity due to the high resistance ratio. However, they have a limited temperature range of -80°C to 260°C, and they 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 a temperature range of -200°C to 260°C.

Applications

• It is widely used in furnaces for automatic temperature measurement.
• Due to its compactness, it replaces conventional thermometers as well as thermocouples thus eliminating the use of lots of wires.
• Used in medical and chemical laboratories to detect very low temperatures (like dry ice and liquid nitrogen).
• Due to electrical output, it is used wherever a feedback system is required and corrective action is thus taken in an automated system.

Wide choice of sensor type, element materials, and configurations can sometimes be intimidating for you to select the right product, our team of experts is always at your disposal to help you chose the right product for your measurement needs. For more info, Get in touch with us!