TMT142B

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 influence of cold‑junction temperature variation), weak thermoelectromotive force is amplified, and linearization is performed (as thermoelectromotive force has a non‑linear relationship with temperature). For RTD signals: typically powered by a constant‑current source, resistance variation is converted into voltage variation, which also undergoes linearization (owing 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. Featuring strong anti‑interference capability, it is suitable for long‑distance transmission to control systems.

High‑end Application

The single‑channel iTEMP TMT142B temperature transmitter with backlit display delivers reliable, accurate and long‑term stable measurement results under harsh operating conditions and in hazardous areas. Equipped with a built‑in Bluetooth® interface for secure remote operation via the Endress+Hauser SmartBlue app, it features a robust single‑compartment field housing. It connects to Resistance Temperature Detector (RTD), thermocouple (TC), resistance (Ω) or voltage (mV) signals, converts them into 4 … 20 mA signals with HART®7 communication.