To enhance the accuracy and dynamics of air temperature measurement, especially for applications in interferometry and machine calibration, a new highly dynamic temperature sensor has been developed. Most of the demand for this development came from the area of machine tool calibration and other application areas of laser interferometry where the need for accuracy is always growing. The limiting factor for the accuracy of laser interferometry in air is having exact knowledge of the airs refractive index, which strongly depends on the air temperature. In addition, there is an emerging desire to temperature sensors on moving parts, such as measuring reflectors on moving tables. To follow temperature changes with moving sensors especially in non air-conditioned rooms is a very challenging task for the sensor dynamics.
The newly developed sensor is based on Pt-wire made from ceramic substrate. Due to its symmetrical construction there is no directionality in the sensors dynamic properties. The surface is passivated so that the sensor can be calibrated in a wet media.
Because of its low mass and the very thin cylindrical ceramic carrier substrate the sensor is can be fragile. To prevent accidental damage a protective cover is available. The sensor can be used both with or without the protective cover. The protection cover makes the sensor take up more space but has very little influence on its dynamic properties.
To enhance its accuracy the sensor is usually equipped with integrated measurement electronics (wired or wireless) which allows the calibration of the whole measurement chain at the same time. A climate station with connectivity for up to 15 wired and 15 additional wireless sensors is also available.
The following performance has been achieved with the sensor:
The above graph shows the performance of the new sensor (blue) in comparison to a conventional sensor with a flat measuring resistor in a slotted protection cap (green). To provoke a realistic temperature change a table with the sensors mounted on it was moved over a heat source and removed again after some time. It is clearly visible that the newly developed sensor is significantly faster. This also allows the detection of turbulent air flow where the conventional sensor only outputs smooth values.
The newly developed high dynamic temperature sensor also has many fields of use besides interferometry. The ealuation of the quality of climatized rooms and monitoring surveillance of measurement chambers or climate chambers are examples of this.
The new temperature sensors were the result of a joint research project between the TU Ilmenau, Institute for Process Measurement and Sensor Technology, and SIOS Meßtechnik GmbH. The project was funded by the German Federal Ministry for Economic Affairs and Energy.