Journal Archive

Platinum Metals Rev., 1964, 8, (4), 146

Platinum Films as Temperature Probes

French Studies on Aviation and Rocketry Applications

Increasing efforts by the French aviation industry to develop new aircraft and rockets have led to a considerable volume of research on all aspects of engine design.

Powder propellants present special probems of ignition and to monitor the ignition of powder composites by shock-waves a probe with fast temperature response is needed which also can resist the high temperatures and chemical conditions which may occur.

M. Scagnetti and J. Crabol have described such a probe in La Recherche Aerospatiale, 1963, (November-December), 23-30. It consists of a platinum film deposited on a silica support which then is incorporated in the wall of the shock-tube so that it is exposed to the same heat flux between powder and ignited gas as the rest of the tube. It is necessary to allow for the difference between the materials which make up tube and probe and the article explains how this can be done.

The probes are part of a modified bridge circuit and register changes in heat flux as small changes in voltage. These can be converted easily to temperatures in degrees Centigrade and show how the temperature varies continuously over the first millisecond after ignition. A series of probes is used along the length of the shock-tube to study variations at different distances from the orifice.

C. Vautier and A. Colombani (Compt. rend., 1964, 258, (19), 4706-4709) also report that platinum films act as fast and accurate resistance thermometers over the range from o to 500°C. Their films were different in that they were deposited on tungsten filaments but their work confirms that there is considerable scope for further developments in the use of platinum films for temperature measurement.

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