For the efficient operation of industrial HVAC and refrigeration systems, accurately and reliably monitoring the temperature of refrigerants and lubricating oil at various stages of the refrigeration cycle is essential. Temperature sensors made from thermistors have become the mainstream choice due to their cost advantages and resistance to media exposure.
Platinum (Pt) exhibits a change in electrical resistance with temperature variation, along with excellent reproducibility and stability. Sensors utilizing this physical property of platinum are known as platinum resistance temperature detectors (RTDs). Platinum RTDs offer high accuracy, excellent stability, and a wide operating temperature range. When encapsulated in a metal housing, they can be immersed in any fluid medium requiring measurement, making them the most commonly used temperature detectors for low to medium temperature ranges (-200°C to 500°C). RTDs are typically used in conjunction with display instruments and computers.
According to the IEC60751 industrial platinum resistance standard, PT100 (R0=100Ω) and PT1000 (R0=1000Ω) are standardized specifications for platinum RTDs.
The sensor's resistance value is critical for determining temperature. However, the copper (or nickel, etc.) connecting wires attached to the sensor possess different characteristics-such as temperature-dependent resistance, linearity, and baseline resistance-that can affect actual measurements. Therefore, based on application requirements, RTD connections are configured as two-wire, three-wire, or four-wire systems. The two-wire configuration is significantly influenced by lead wire resistance and is only used in applications with low accuracy requirements. By introducing a third wire, the following measurement process can be implemented: first, measure and record the resistance between wire 2 and wire 1; then, measure the resistance between wire 2 and wire 3; finally, subtract this value from the initially measured resistance. The remaining value represents the resistance of the temperature element itself (excluding leads). This is the three-wire configuration. The three-wire configuration typically meets general industrial requirements and offers the greatest economy in terms of equipment simplification and cable reduction. Of course, if a four-wire configuration is feasible, it substantially improves errors caused by factors such as uneven wire lengths, different wire diameters, resistance changes due to wire oxidation, and environmental differences between wires.
Mihui Technology provides temperature sensors in various packaging forms according to on-site requirements, as shown in the figure below. For additional requirements, please contact the factory directly. For more information, please visit our website at www.mihuitec.com.
