How it works
The core principle of a temperature transmitter is to convert the non‑electrical quantity (temperature) detected 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‑end temperature variation). The weak thermoelectric voltage is amplified and linearized, as thermoelectric voltage exhibits non‑linear characteristics versus temperature.
For RTD signals: powered by a constant‑current source in typical operation, the resistance variation is converted into voltage variation, which also undergoes linearization owing to the non‑linear resistance‑temperature relationship.
The circuit further filters signals to suppress interference. Conditioned voltage signals are fed to the voltage‑to‑current conversion circuit (V/I converter), which accurately outputs the industry‑standard 4 to 20 mA DC signal (or other standard signals). The magnitude of this current signal has a linear correspondence with the measured temperature range. With strong anti‑interference capability, it is suitable for long‑distance transmission to control systems.
Key features
• High reliability, excellent long‑term stability and high measurement accuracy, equipped with diagnostic functions.
• Installed in Class B heads of industrial and sanitary thermometers.
• DIN rail‑mounted instrument for control‑room installation.
• Inputs for RTD or thermocouple thermometers.
• Parameters or pre‑configuration can be set at factory.
• Push‑in terminals enable fast installation and maintenance without tools.
• CvD sensor‑transmitter matching function for optimized measurement accuracy.
• Diagnostic information complies with NAMUR NE107.
• Explosion‑proof certified for enhanced safety.
Typical applications
The iTEMP TMT31 is a 4 to 20 mA temperature transmitter, designed for users across various industries who require easy selection, convenient installation and simple operation. This single‑channel 4 to 20 mA temperature transmitter delivers reliable measurement with excellent long‑term stability. The modular instrument can be optionally mounted directly in Class B heads or on DIN rails inside control‑room cabinets. The iTEMP TMT31 supports connection to various Pt100 and Pt1000 RTD sensors, as well as thermocouple sensors of different calibration types.
