Electrical resistance changes

The sensation of warmth or coldness is caused by temperature. Adding heat to a substance not only raises its temperature, but also produces changes in several other qualities. The substance expands or contracts its electric resistance changes and in the gaseous form, its pressure changes. Five different temperature scales are in use today Celsius, Fahrenheit, Kelvin, Rankine, and international thermodynamic. 

Acid copper sulphate test t 16 wt.% H2SO4 -1-100 g/l CuSO, (-1- metallic copper) 72 h exposure to boiling solution 1. Appearance of sample upon bending 2. Electrical resistivity change 3. Change in tensile properties -1- 0-30 to -1- 0-58 Chromium-depleted area... 

Sensors following the principle of heat of reaction , so-called Pellistors , see Fig. 3.17, serve as indicators for flammable gases. With the catalytic conversion of fuel gases on the surface of a heated sensor, its electrical resistance changes proportionally to the concentration of the gas. 

For this reason an apparatus for determining thermal stability on the basis of electrical resistance change (3) was designed, and an automatic device for exposing PVC strip specimens to a gradient increase of heating time at the test temperature was built. 

All metals have the characteristic that their electrical resistivity changes with temperature. For most materials the resistivity increases with temperature, and for most metals and alloys that are used as bridges in hot-wire initiators, this relationship is linear. 

A bolometer has a conducting element whose electrical resistance changes as a function of temperature. Bolometers are fabricated from thin strips of metals, such as nickel or platinum, or from semiconductors consisting of oxides of nickel or cobalt the latter are called thermistors. 

Enzyme thermistors, where the thermal effect of the chemical or biological reaction is transduced into an electrical resistance change. 

Transducers Many measurements cannot be used for control until they are converted to physical quantities (such as electric voltage or current, or a pneumatic signal, i.e., compressed air or liquid) which can be transmitted easily. Transducers are used for that purpose. For example, strain gauges are metallic conductors whose electric resistance changes when they are subjected to mechanical strain. Thus they can be used to convert a pressure signal to an electric one. 

Data of the relative electrical resistance changes from the 18 sensors can combine with every sample to form a matrix (see Fig. 2 The library data base) and the data is without preprocessing prior to chemometrics analysis. The sensor response is stored in the computer through data acquisition card and these data sets are analyzed to extract information. 

Simultaneous contact potential differences (CPD) and electrical resistance changes of an Sn02 sensor (operated at 300°C) with stepwise increasing amounts of oxygen (100,300,500,1000,2000 and 2500 ppm). 

Todoroki A, Omagari K, Shimamura Y, Kobayashi H. Matrix crack detection of CFRP using electrical resistance change with integrated surface probes. Compos Sci Technol 2006 66(11—12) 1539—45. http //dx.doi.Org/10.1016/j.compscitech.2005.l 1.029. 

Iwasaki A, Todoroki A. Statistical evaluation of modified electrical resistance change method for delamination monitoring of CFRP plate. Struct Health Monit Int J 2005 4(2) 119-36. http //dx.doi.org/10.1177/1475921705049757. 

Hirano Y, Todoioki A. Damage identification of woven giaphite/epoxy composite beams using the electrical resistance change method. J Intell Mater Syst Struct 2007 18(3) 253-63. http //dx.doi.0rg/lO.l 177/1045389x06065467. 

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