TMT71

The core principle of a temperature transmitter is to convert the non‑electrical quantity (temperature) sensed by temperature sensors into standard electrical signals. It interfaces with sensors such as thermocouples (TC) or Resistance Temperature Detectors (RTD). For thermocouple signals: cold‑junction compensation is implemented (to correct the effect of cold‑junction temperature variation), weak thermoelectromotive force is amplified, and linearization is performed (as thermoelectromotive force exhibits non‑linearity versus temperature). For RTD signals: typically powered by a constant‑current source, the change in resistance is converted into a voltage variation, which also undergoes linearization (due to the non‑linear resistance‑temperature relationship). The circuit also filters signals to suppress interference. The conditioned voltage signal is fed into a voltage‑to‑current conversion circuit (V/I converter), which accurately converts it into the industry‑standard 4‑20 mA DC current signal (or other standard signals). The magnitude of this current signal corresponds linearly to the measured temperature range. With strong anti‑interference capability, it is suitable for long‑distance transmission to control systems.

Mid‑range Application

It delivers unmatched reliability, measurement accuracy and long‑term stability when deployed in critical process sections across all industries. This configurable transmitter accepts not only RTD and thermocouple (TC) signals but also resistance and voltage signals, and converts them into output signals. Standard 4 … 20 mA output signals are used for process measurement. Commissioning, operation and maintenance are fast and straightforward; the transmitter can be operated via configuration software on a PC or through Endress+Hauser SmartBlue utilizing the integrated Bluetooth® technology.