Very high temperature sensors

Lubricants have a nonlinear viscosity coefficient against temperature. At very low or very high temperature this nonlinearity can create significant measurement failures. A careful analysis will show this effect within the transmission chain. Sticking is the worst case. It can happen that frozen water makes a short cut in torque sensors. In most cases damping factors are based on the electrical filter circuits (Fig. 7.12.13). 

The electrical resistivity of the implant layer (shown in Fig. 6), demonstrates two features that are important for temperature sensor applications [25]. First, the TCR of the material is very large, typically 1.0 Mft per 25 C, resulting in very high temperature resolution. Second, the 2.0 Mfl/sq resistance of typical small sensors... 

Savrun, E. (2002) Packaging considerations for very high temperature microsystems. Proceedings, IEEE Sensors 2002, Orlando, FI, 12-14 June 2002, vol. 2, pp. 1139-1143. 

Electric tube furnaces of appropriate dimensions are available from various manufacturers. A model RO 4/25 by Heraeus GmbH, Hanau, FRG is suitable. However, a very satisfactory furnace can be built by any well equipped laboratory workshop at little cost and effort. The material required consists of thin walled ceramic tubing, 3.5 cm i.d., nichrome resistance wire, heat resistant insulation, and ordinary hardware material. A technical drawing will be provided by the submitters upon request. The temperature of the furnace can be adjusted by an electronic temperature controller using a thermocouple sensor. A 1.5 kW-Variac transformer and any high temperature thermometer would do as well for the budget-minded chemist. 

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