An RTD ( resistance temperature detector) is a temperature sensor that operates on the measurement principle that a material’s electrical resistance changes with temperature. The relationship between an RTD’s resistance and the surrounding temperature is highly predictable, allowing for accurate and consistent temperature measurement. By supplying an RTD with a constant current and measuring the resulting voltage drop across the resistor, the RTD’s resistance can be calculated, and the temperature can be determined.

Different materials used in the construction of RTDs offer a different relationship between resistance and temperature. Temperature sensitive materials used in the construction of RTDs include platinum, nickel, and copper; platinum being the most commonly used. Important characteristics of an RTD include the temperature coefficient of resistance (TCR), the nominal resistance at 0 degrees Celsius, and the tolerance classes. The TCR determines the relationship between the resistance and the temperature. There are no limits to the TCR that is achievable, but the most common industry standard is the platinum 3850 ppm/K. This means that the resistance of the sensor will increase 0.385 ohms per one degree Celsius increase in temperature. The nominal resistance of the sensor is the resistance that the sensor will have at 0 degrees Celsius. Although almost any value can be achieved for nominal resistance, the most common is the platinum 100 ohm (Pt100). Finally, the tolerance class determines the accuracy of the sensor, usually specified at the nominal point of 0 degrees Celsius. There are different industry standards that have been set for accuracy including the ASTM and the European DIN. Using the values of TCR, nominal resistance, and tolerance, the functional characteristics of the sensor are defined.

Dpstar manufactures Maltec-RTDs for many industrial applications. From single- or dual-element RTDs to Pt100’s we have the right sensor. 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.

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