Resistive conductive-type temperature

The conductive-type temperature sensor (RTD) uses a metal element to measure temperature. The resistance of most metals increases with temperature thus, by measuring resistance, one can determine the temperature. Platinum is used where very precise measurements are required and where high temperatures are involved. Platinum is available in highly purified condition it is mechanically and electrically stable and corrosion-resistant. Most of the RTD sensors have a wound wire configuration although for some applications, metal-film elements are used. 

The list of materials which displayed such type of behaviour contains amorphous Mo Gei j, [1] and Moa,Sii a [2] films, amorphous InOx films [3, 4], ultrathin films of Be [5], crystalline films of Nd2-a Cea Cu04+y [6, 7]. Two typical examples of such sets of curves relevant to different limits are presented in Figs. 1 and 2. In Nd2-a Cea Cu04+ / (Fig. 1) the growth of the resistance with decreasing temperature on the non-superconducting side of the field-induced transition was below ten percent so that it reminded more a metal with quantum corrections to its conductivity than an insulator. In amorphous InO (Fig. 2), typical for insulator exponential temperature dependence of the resistance resulted in almost tenfold increase of the resistance. 

Based upon the experimental data it was deduced that the chemical bonding in Zintl phases should be a mixture of covalent, ionic and metallic contributions ". As metallike systems the B32-type compounds Aj Bj possess a distinct phase width in the range of approximately 0.45 < x 0.55 . Furthermore one finds a metallic conductivity in these systems and as in metals the electrical resistivity increases with temperature . ... 

If a filler is used it should be a non-conductive material and may be treated with a coupling agent appropriate to both filler and resin type. The filler should be highly moisture resistant, should withstand temperatures up to 120 °C without degradation, and should have a maximum particle size of 0.1 mm. 

Temperature can be measured with resistive temperature sensors, thermocouple temperature sensors, and radiation pyrometers. There are two types of resistive temperature sensors the conductive type and the semiconductor type. Both operate on the principle that the resistance of sensor material changes with temperature. 

A dense and electronically insulating layer of L1A102 is not suitable for providing corrosion resistance to the cell current collectors because these components must remain electrically conductive. The typical materials used for this application are 316 stainless steel and Ni plated stainless steels. However, materials with better corrosion resistance are required for long-term operation of MCFCs. Research is continuing to understand the corrosion processes of high-temperature alloys in molten carbonate salts under both fuel gas and oxidizing gas environments (29, 28) and to identify improved alloys (30) for MCFCs. Stainless steels such as Type 310 and 446 have demonstrated better corrosion resistance than Type 316 in corrosion tests (30). 

In the described techniques, the contact resistance-related issues usually are more typical in the through-plane measurements than in the in-plane measurements. However, surface conductivity measurements are also affected by the contact resistance. These types of experiments are sensitive to undesired electric noise (Tong 2011). Also, the qualities of all electric connections are of great importance. Preconditions for reliable results are careful construction of the measuring unit and sample preparation and quality management of testing procedures with reference probes. The environment has effects on the conductivity values and temperature, but humidity in particular may cause inaccurate results (Boudenne et al. 2011). 

Silicone elastomers are heat, aging, and chemical resistant. They are characterized by having unmodified mechanical properties over a wide temperature range from -70 to 200 ""C. Standard types are available in a hardness of 20 to 90 Shore A. Electrically conductive types, fluorosilicone types, oil-bleeding, fast cross-linking, and hard modified types are offered. 

Figure 4 shows the temperature dependence of the molar conductivity of AMPS, PAMPS, and a PAMPS gel. In general, unlike electron conductance of metals, carriers of ionic polymer gels are ions. Hence, electrical resistance decreases as temperature increases. This trend shows an Arrhenius-type temperature dependence as seen in semiconductors. 

Plastic materials should not be selected solely on the basis of published chemical resistance data. The type of test conducted, test temperature, media concentration, duration of exposure, type of loading, and additives used in the base polymer must be considered, since each of the above-mentioned factors can have a significant effect on the chemical resistance of plastics. The risk potential of premature failure can be minimized by conducting the test under anticipated end-use conditions and media (5). 

The electrical resistivity at room temperature is about 10 Q-cm. The conductivity increases with rising temperature according to the exponential law valid for semiconductors. The temperature coefficient indicates p-type conductivity, Gerasimov et al. [12]. Deviations from the stoichiometric Se content immediately lead to semimetallic behavior, Bozorth et al. [15]. Values Q = 3 X10 and 1.2 x 10" Q cm at 20 and 300°C are given by Yarembash et al. [17]. An appreciably lower resistivity q = 2.4x10" Q-cm at room temperature, a negative Hall coefficient, and a carrier density of 3x10 cm" are reported by Miller etal. [18]. 

---