![]() In one version of this technique a conductive sheet under test is placed between two coils. ![]() This method measures the shielding effect created by eddy currents. For a rectangle an appropriate geometric factor is added. ![]() Resistance across a square area will be measured in Ω/sq. Measurement may also be made by applying high-conductivity bus bars to opposite edges of a square (or rectangular) sample. For more details see Van der Pauw method. Two common arrays are square and in-line. A geometry factor needs to be applied according to the shape of the four-point array. Typically a constant current is applied to two probes, and the potential on the other two probes is measured with a high-impedance voltmeter. can be found using Irvin's curves, which are numerical solutions to the above equation.Ī four-point probe is used to avoid contact resistance, which can often have the same magnitude as the sheet resistance. Sheet resistance is invariable under scaling of the film contact and therefore can be used to compare the electrical properties of devices that are significantly different in size. The utility of sheet resistance as opposed to resistance or resistivity is that it is directly measured using a four-terminal sensing measurement (also known as a four-point probe measurement) or indirectly by using a non-contact eddy-current-based testing device. Examples of these processes are: doped semiconductor regions (e.g., silicon or polysilicon), and the resistors that are screen printed onto the substrates of thick-film hybrid microcircuits. It is commonly used to characterize materials made by semiconductor doping, metal deposition, resistive paste printing, and glass coating. It is usually a measurement of electrical resistance of thin films that are uniform in thickness. Sheet resistance, is the resistance of a square piece of a thin material with contacts made to two opposite sides of the square. Resistor based on the sheet resistance of carbon film
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