2 – Wire RTD
  • Low accuracy
  • Measurement errors
  • Less expensive
  • Connecting wires should not be lengthy
  • Simplest circuit design
  • A single lead wire connects to each end of the element
  • The resistance in the circuit is calculated by measuring the resistance in the lead wires and connectors
  • This results in some degree error or readout that is higher than the actual measured temperature. This can be eliminated with calibration
3 – wire RTD
  • Better accuracy than 2 -wire
  • Fewer errors
  • Less expensive than the 4 wire
  • The wires which are used should have the same length, Long connecting wires can be used
  • The three wire configuration is the most used in industrial applications
  • Two wires are connected to one end of the sensor, RL2 and RL3, and to the monitoring device. The third wire, RL1, is connected to the element
  • The three wires are of equal length, so their resistance is equal
  • The 2-wire configuration also has errors that have to be adjusted by calibration.
4- wire RTD
  • High accuracy
  • Won’t be any error
  • Very expensive
  • Long connecting wires can be used
  • The four wire configuration is the most complex
  • DC current is provided through two leads, RL1 and RL4. The voltage drop is measured by the other two leads, RL2 and RL3.
  • The voltage drop and current are known, making the resistance easy to read as well as the temperature across the system.
  • The 4-wire configuration is time consuming, and expensive to install but produces the most accurate and precise readings.