Thin Film Thermometer MTFT
Measuring Highly Transient Temperatures
Thin film thermometers consist on a ceramic substrate of zirconium oxide on which a thin film of nickel is deposited. This sensor is a magnitude more sensitive than our thermocouples. Temperature changes of only 0.1 K can be measured. The gauges can measure static to high transient surface temperatures with response times in the range of microseconds.
Due to the open metal film these sensors are quite sensitive but also delicate. Therefore for measurements in clean conditions and moderate heat fluxes the Thin Film Thermometer are recommended, whereas in harsh environmental conditions or high heat fluxes our Coaxial Thermocouples MCT is the better choice.
The MTFT are powered by a constant current source. The change of the film resistance leads to voltage changes proportional to the temperature change. The temperature change corresponds to
ΔT = (R – R0) / R · α
For transient temperature changes the Thin Film Thermometer is connected to our MFA 1000 Amplifier and power supply. This device has a bridge amplifier and offers constant current and voltage.
To mount the sensor we recommend gluing the gauge into the wall. Alternatively we provide a wall mount adapter for easy reuse. As an advantage to competitive thin film sensors we pass two platinum wires through the substrate soldered to the film. These embedded connections eliminate the challenge of connecting wires to the thin leads and makes the wall mount much easier. Further these two wires are extended with four cables, two for current supply, and two for measuring.
There are multiple applications for this type of sensor. The gauges are suitable for measuring constant temperature over time, but transient measurements e.g. testing wind tunnel models give their superior field of application, the change of cylinder wall temperature in a piston engine or for calculations of heat flux in a re-entry phase on a rocket model in a hypersonic wind tunnel.
In the case of measuring the re-entry simulation on the space shuttle Hermes, thin film thermometers were used on the surface of the delta wings, where smaller temperature changes were expected. Our thermocouples were used in the nose of the wing due to the very high heat flux, the higher mechanical stability and the adaptive sensor head to the curved surface.
Publication on Applications
Dr. Müller Instruments
Tel.: +49 - 6172 - 380 37 27
Fax: +49 - 6172 - 177 077 4
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