TOPRO Launches Temperature Transmitters as a New Product Category

Temperature Transmitters

A temperature transmitter is an electrical instrument that interfaces a temperature sensor (e.g. thermocouple, RTD, or thermistor) to a measurement or control device (e.g. PLC, DCS, PC, loop controller, data logger, display, recorder, etc.). Typically, temperature transmitters isolate, amplify, filter noise, linearize, and convert the input signal from the sensor then send (transmit) a standardized output signal to the control device. Common electrical output signals used in manufacturing plants are 4-20mA or 0-10V DC ranges. For example, 4mA could represent 0°C and 20mA means 100°C. 
TOPRO Electrical Technology launches four types of temperature modules: TW-01 Rail Mounted Thermocouple Temperature Transmitter, TW-02 Head Mounted Thermocouple Temperature Transmitter, TW-11 Rail Mounted RTD Temperature Transmitter and TW-12 Head Mounted Thermocouple Temperature Transmitter.

Temperature Transmitter Inputs

A thermocouple sensor is a pair of dissimilar metal wires joined at one end. The junction produces a low level voltage proportional to the difference in temperature between the open and closed ends. 

An RTD or Resistance Temperature Detector is a passive circuit element whose resistance increases with increasing temperature in a predictable manner.

A temperature transmitter works by connecting to it some form of temperature sensor. For example a RTD (Resistance temperature device) or Thermocouple. In the case of a RTD connected to the transmitter the transmitter measures a change in resistance of the RTD proportional to the change in temperature measured. The transmitter then derives a current output (generally 4-20mA) which can be measured by an instrument, such as a PLC, loop indicator ect. In the case of a thermocouple a Milli voltage is produced at a junction of two dissimilar metals, this change in Milli voltage again proportional to the change in temperature and the transmitter again derives a current output measurable by a instrument. The transmitter will be ranged by a programming device, say for example an application where process temperatures need to be measured between 0-100 degrees, the transmitter will be ranged 0-100 degrees and thus give an output proportional to the temperature measured by the sensing element. 0 degrees = 4mA, 100 degrees = 20mA. A excitation supply will be connected to the transmitter and the 4-20mA will flow in this loop back to the measuring instrument. It is necessary to use the correct type of sensor for the application to get the best accuracy when measuring. RTD's are generally used for measuring lower temperatures where as thermocouples are used for measuring higher temperatures. There are several types of RTD's such as 2 wire, 3 wire and 4 wire and an even greater range of thermocouples depending on the temperatures and measuring environment.