RTD stands for resistance temperature detector, and it is a type of temperature sensor. These sensors change resistance as temperature changes. The resistance increases when the temperature of the sensor increases. The sensor works on a resistance versus temperature relationship. It is essential to keep in mind that these are passive sensors and do not produce an output of their own. To compensate for this issue, an external electronic device is used to measure the sensor's resistance. This is done by passing small electrical currents through the sensor to generate a voltage.
· 2-Wire
· 3-Wire
· 4-Wire
A 2-wire RTD uses a single wire to connect both ends of the RTD element. This construction is the most simplistic form of an RTD. All resistance calculations include circuit elements, meaning that there is a higher degree of error due to the wire resistance. Two-wire RTDs are best in applications that require short wires and high resistance sensors. Most importantly, high accuracy should not be the essential factor.
A common wire construction is a 3-wire construction. One side of the element has one wire connected, and the other side has two wires attached. Adding these extra connections allows the device to reduce the extra resistance created within the circuit due to the wires. A 3 wire RTD, unlike the two-wire variant, may give a more accurate reading.
A 4-wire RTD is more complex compared to the two other types. You can often find these RTD's used in laboratory applications that require the highest possible levels of accuracy. This type of RTD assembly can quickly compensate for errors created through wire resistance.
Sensor Scientific, Inc | All Rights Reserved