Temperature measurement bimetallic-strip

Cantilever deflections are also caused by small changes in temperature, because the usual fabrication produces a bimetallic strip configuration. Thus the AFM arrangement could be used to measure tiny thermal changes that arise in electrochemical cells. Applications of this type are just emerging. 

Temperature measurement thermometers, thermistors, thermocouples, radiation pyrometers and bimetallic strips. 

The principle of the thermal expansion of solids is used in bimetallic thermometers, which consist of two metal strips of different materials with different coefficients of expansion firmly connected together. Temperature differences bend these bimetallic springs and they are usually wound in spirals or coUs. The useful measuring range is from —73 to - -537°C with an accuracy of +1% of full scale [4). Bimetallic strips are used for temperature compensation in mechanical instrument movements. They are also used in switching relays to indicate whether a limiting value is exceeded. 

A Tenney environmental test chamber (Model TSU-100) was used as an air bath. Temperature can be controlled to 0.1 °C. by adapting an Aminco bimetallic thermoregulator connected to a supersensitive relay. Samples were prepared in the form of rectangular strips. First, moduli were measured as a function of temperature. At least five minutes was given to each temperature increment ( 5°C.) to obtain thermal equilibrium. 

Bimetallic thermometers measure temperature by the change in physical dimension of the sensor. They have often been used [80]. The sensor consists of a composite strip of material, normally in a helical shape, formed by two different metals Differences in the thermal expansion of the two metals cause the curvature of the strip to be a function of temperature. The strip is used as a temperature indicator with a self-contained scale. Bimetallic thermometers have been used at temperatures from -185 to 425°C. The precision and accuracy of such thermometers are described in Ref. 81. 

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