RTD Two-Wire Transmitters: Introduction, Construction, and Working Discussed

RTD Two-Wire Transmitters: Introduction, Construction, and Working Discussed

There are several types of industrial temperature sensor devices in the market. Thermocouple transmitters, RTD transmitters, temperature controllers, etc., are a few popular temperature sensing devices. RTD sensors are one of the most popular types of temperature detectors out of many available. RTD stands for Resistance Temperature Detector. The device measures the temperature by measuring resistance in electric current flow. The RTDs are further classified according to different configurations or constructions. Depending on the wire configuration, RTDs are classified as 2 wire transmitter RTD, 3 wire transmitter RTD, and 4 wire transmitter RTD. The simplest yet commonly utilized type of RTDs is the 2 wire RTD sensors. This post discusses the configuration/construction and working principle of 2 wire transmitter RTD.

An Introduction to 2 Wire RTD Configuration An Introduction to 2 Wire RTD Configuration

Amongst all types of RTD configurations, 2 wire configuration is the simplest one. It is also known as the 2 lead RTD configuration. The construction features a single lead or wire that connects two ends of the RTD elements to the temperature monitoring devices. The two ends of the wire act as two leads in the series configuration. The series configuration of 2 lead RTD is an open loop circuit. It can only be used for marginal temperature measurement due to the absence of eliminating lead wire resistance.

For the series 2 wire configuration, it is important for the wire leads to be short so that their resistance can be considered without major error. This type of RTD is suitable for 100 meters of cable for a balanced bridge system and fixed bridge system.

This type of RTD configuration is rare yet is used for specific applications. It features a closed-loop by connecting an additional lead or wire as eliminating resistance lead. This closed-loop configuration works similarly to 3 wire RTD configuration but the additional third lead works as compensation ambient changes in the resistance.

A Brief Discussion on Working of a 2 Wire RTD

Similar to the construction, the working principle of a 2 wire RTD is absolutely simple. The following activities only take place while the operation of a 2 wire RTD.

  1. From the input source, the electric current is passed through the RTD element unit.
  2. Generally, short length copper (Cu) wires are utilized for 2 wire RTD configuration. Being electrical conductors, these wires let the electric current pass through but copper (Cu) offers thermal resistance.
  3. Due to the offered resistance, the slight temperature rise takes place inside the lead wires.
  4. The ambient temperature rise is sensed by the RTD.
  5. The leads are connected to temperature monitoring devices which act as temperature detectors in the setup.
  6. This way, the two-wire RTD transmitter operates.


Now that the 2 wire RTD transmitters and introduced and their working is explained, you may want to source RTD sensors for your industrial applications. However, you must source these RTD sensors from trusted manufacture like Therm-x. The company has been manufacturing and supplying premium quality 2 wire RTDs and other types of temperature measurement/control devices like thermocouple transmitters since, 1983.

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