Highly reliable temperature measurement

With Sitrans TH320/420 and TR320/420, Siemens have introduced a new generation of reliable WirelessHART (Highway Addressable Remote Transducer Protocol) temperature transmitters for a wide range of sensor types suitable for mounting in sensor head and rail mounting. These new transmitters offer a clear and precise measurement signal and ease of use. The temperature transmitters have attained safety integrity level (SIL) 2/3 certification according to IEC 61508, so they are particularly suited for safety-critical applications. The devices also have a large number of nation specific explosion protection certificates for all zones. They provide reliable results even under extremely tough conditions up to -50°C. Main application areas include the chemical, oil and gas, marine and power generation industries.

With fast and accurate sensor and transmitter tuning, the use of the Callendar-van Dusen method or 60-point-curve ensures highest measuring accuracy. Deviations can be detected and monitored through the drift detection with dual-channel transmitters, for scenarios such as preventive maintenance. Electronic device descriptions (EDD, DTM and FDI) allow the new transmitters to be used in all current distributed control systems. A quick start wizard is just one example of their user-friendly features. Measurement values, device functions and visual alarm signals can all be displayed and operation planning and implementation is very convenient using special visualisation components for Simatic PCS 7 (Sitrans Library).

When a sensor fails in operation, in situations such as disconnection or short circuit, measurement failures may result in loss of control or halts in production. To avoid this and ensure high measurement availability through reliability and long term stability, maintenance planning is essential. The Sitrans TH420 and TR420 sensor backup function, drift detection and alarm system make this possible. Using the 4 wire connection for both sensors increases data accuracy and reliability as it allows a seamless transition to the second sensor in case the first sensor fails. The continuous balancing of the two independent sensors measuring in parallel, while detecting and monitoring measuring value deviations, allows the scope of maintenance to be planned as needed, in the event of sensor failure thus avoiding production stops. Balancing the sensors using the Callendar-van Dusen method also overcomes the problem of sensor inaccuracy caused by individual deviation from standardised Pt100 curves or by aging. Outstanding transmitter accuracy and sensor balancing enable simpler calibration of the sensors directly in the transmitter and provide for highly precise individual values.