In response to the growing demand for high-precision platinum temperature sensors, IST AG is launching a new RTD PW series for high-precision measurements. The new 4-wire design on-chip allows measurements in class F0.15 up to +600 ° C with very low hysteresis.
Platinum temperature sensors are characterized by a high long-term stability and high robustness, e.g. with vibrations. Also, in contrast to e.g. thermocouples, they send out an output signal in relation to the absolute temperature, which is why they are often used for reference purposes.
For high-precision temperature measurements, 4-wire constructions have proven to be efficacious as they can effectively suppress wire resistances and their temperature influences. There are various possibilities for the placement of the reference point. For two-wire sensors the four-lead extension is typically placed at the wire end – the extension point is the reference point. This design can often lead to measurement inaccuracies, for example due to possible thermal stresses when using different wire materials or due to minor position changes.
Further, the alternative attachment of the extensions directly on the welding pads has proven to be less than optimal: covering the welding points (glob-top) in favour of strain relief can lead to mechanical tension, and the installation of the sensor can result in drifts.
Innovative Sensor Technology IST AG has studied and dealt with this problem intensively and has developed a new sensor which is especially designed for the needs of high-precision and long-term stable measurements. With this new 4-wire RTD, the reference points are inside the sensor chip (see number 3 in image below). The splitting onto four extended wires already happens in the meander area and outside the glob-top. As in the entire other meandering area, high-purity thin-film platinum is used here. This suppresses the contact resistance in this area and minimizes the influence of mechanical stress due to or on the glob-top. The continuation of the four extended wires with pure platinum wire guarantees a minimal material variation from the chip side, enabling a high long-term stability and the suppression of thermal stress.
By using the already established PW technology, a very good performance on the characteristics curve is achieved (according to IEC 60751) – the class F0.15 can be guaranteed in a temperature range of -200 ° C to +600 ° C. Furthermore, the construction features reduced hysteresis, making the sensors suitable for measurements at very low temperatures as well.
For more information, please visit https://www.ist-ag.com.