Temperature transmitters

High-quality temperature transmitters from WIKA

Temperature transmitters are a fundamental component in the industry. These temperature transmitter devices convert the input signal from a wide range of temperature sensors, such as resistance thermometers, thermocouples, and potentiometers, into a standardized analogue or digital output signal. The WIKA standard analogue outputs for temperature transmitters are 0…10 V or 4 … 20mA. 4…20 mA is the predominant output signal as many industries have adopted this standard for current loop communication. WIKA also offers standard digital outputs of HART, FOUNDATION™ Fieldbus protocol and PROFIBUS® PA (Process Automation).These Smart temperature transmitters are a two-way communication platform resulting in enhanced diagnostics for the device(s), free configuration of the sensor and measuring range, error signalization or measuring point identification.

What is a temperature transmitter?

Temperature transmitters convert the temperature-dependent change in resistance of resistance thermometers or the temperature-dependent change in voltage of thermocouples into a standardised output signal (e.g. 0 ... 10 V or 4 ... 20 mA). With these standardised signals, measured temperature values can be transmitted easily and reliably.

Until the introduction of the temperature transmitter, the raw measured values of the sensor were only transmitted to the control room via cable and then converted and processed there. These days, this form of transfer is only used in specific cases, for example, if the ambient temperature is too high or the installation situation is too restricted. For tasks of this type, rail-mounted transmitters also offer a solution. In almost all standard applications, however, head-mounted transmitters have prevailed.

What are the advantages of temperature transmitters?

With the help of a temperature transmitter, not only can users collect measured values digitally via fieldbuses or different protocols, such as HART® or company-specific systems that work parallel to the 4...20 mA output loop, but they can also completely configure the instruments. The relevant elements here are, primarily, the selection of sensor input and measuring range, the storage of measuring location identifiers such as TAG numbers and M&C descriptions as well as the adjustment of the measuring signal by an offset or a specific characteristic curve of the sensor.

A further feature of the modern temperature transmitter is the diagnostic functionality: The instrument not only measures the value from the sensor and converts it into the desired temperature unit, it also checks many relevant parameters in the background, e.g. lead resistances, the internal electronics temperature and the supply voltage. If errors occur, the temperature transmitter immediately sends a corresponding signal. In this way, errors such as sensor breaks and short-circuits, effects of the lead and, when using dual sensors, even the drift of a measured value can be detected.


What should be considered when measuring temperature with thermocouples?

For temperature measurement using thermocouples, a reference value is always needed and/or a compensation must be made. Thus, there is a sensor built into the digital transmitter (Pt100) which measures the terminal temperature (ambient temperature) ...


What is galvanic isolation?

An isolation of the signal between the signal side and the output side (e.g. through coils).