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Why you measure resistivity and not resistance in four probe method?
Wiki User
∙ 13y ago
Resistivity is a constant for a material as opposed to resistance which is dependent on size considerations. This is analogous to specific heat capacity and heat capacity. It can be said that resistivity is more useful for comparison because other factors (size) have been accounted for.
In the case of using the four-probe method to measure the thickness of a thin film:
ρ = (V/I) x (thickness of film) x (correction factor)
We measure the current and voltage using the four-probe method, from which we can get the resistance between the probes. Knowing the resistivity, which is constant for the material and can be obtained from sources such as books, will enable us to relate the resistance to the dimensions of the film.
Wiki User
∙ 13y ago
Wiki User
∙ 11y agoFour probe method for measuring resistance is also known as Four-terminal sensing or 4T sensing. It is a technique to measure electrical impedance. It uses separate pairs for current carrying and voltage sensing electrodes. This method is capable of making more accurate measurements than two terminal sensing.
In this method, current is supplied via a pair of current leads. The voltage drop across the impedance is measured by a separate pair of leads. Thus, the voltage drop in the current carrying wires is prevented from being added to the actual value.
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The last color code on the resistor is the tolerance marking it can be from zero up to 10% and higher , then there is other resistances that will influence the measurement, like meter probe tips and even the resistance in the probe wire especially on lower value resistors one can test it by connecting the two probes it is almost impossible to get a zero reading
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volume of material used
Why two probe method is better than four probe method?
the question is wrongfour prob is better than two prob method as it eliminates the effect of wire imbedance as well as contact resistance
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What is the advantage of four probe method over other conventional methods?
I assume you are referring to methods of measuring small value resistances, as in locating short circuits on a PC card. Two probe is the method used by standard ohm meters. This works OK for most resistance values, as the resistance of the leads & probes is much lower than the resistance being measured. But when the resistance being measured gets very tiny (e.g. a few milliohms) it fails as the resistance of the leads & probe are of the same order of magnitude and are in series with it. Four probe solves this problem by using two probes connected to a current source to drive the resistance and a separate two probes connected to a precision voltmeter calibrated in milliohms. The voltage drop in the leads due to the test current does not get measured by the calibrated voltmeter, as it does in two probe method. There is no voltage drop in the measurement leads as the voltmeter is high impedance.
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You cannot determine band gap by four probe method.
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In general, line resistance = resistivity * line length / (line cross-sectional area). Check the unit consistency: for the right-hand side, [ohm-m] * [m] / [m^2] = [ohm]. The resistivity of the material should be given. You can measure it with a large chunk of the material using a four-point probe, simplistically speaking. You can also look up the value online.
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Air Probe.
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A temperature probe is a digital thermometer.
