Advantages of four probe method

In summary, in four probe method, you measure potential drop between the center 2 terminals. You can't alter the distances between the probes which measure voltage, but you theoretically could change the function of the probes.
  • #1
ruchika
3
0
how does contact resistance and sprearding resistance gets in eliminated in four probe technique for measuring resistivity in comparison to two probe technique where we encounter these resistances?
 
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  • #2
It should be fairly obvious if you draw a circuit diagram.
In the ideal case (perfect current source and voltmeter with inifinite input impedance) the series/contact resistance is eliminated simply because the current is the same in the whole circui (no current flows into the voltmeter) and the voltmeter is only measuring across the sample.
Since you know the current and the voltage you then calculate the resistance from Ohms law

Note that there are of course instances where non-ideal effects come into playl; e.g..when measuring samples with very high (several megaohms) or low resistance (milliohms); so it is important to understand how the technique actually works.

Edit: I just realized that I assumed you were referring to "through" measurements (e.g. a resistor), but since you are referring to resistivity you might actually be asking about van der Paw measurements (of e.g. thin films)?
 
  • #3
May I come to know that how the current remains constant throughout the resistance.
f95toli said:
It should be fairly obvious if you draw a circuit diagram.
In the ideal case (perfect current source and voltmeter with inifinite input impedance) the series/contact resistance is eliminated simply because the current is the same in the whole circui (no current flows into the voltmeter) and the voltmeter is only measuring across the sample.
Since you know the current and the voltage you then calculate the resistance from Ohms law

Note that there are of course instances where non-ideal effects come into playl; e.g..when measuring samples with very high (several megaohms) or low resistance (milliohms); so it is important to understand how the technique actually works.

Edit: I just realized that I assumed you were referring to "through" measurements (e.g. a resistor), but since you are referring to resistivity you might actually be asking about van der Paw measurements (of e.g. thin films)?
 
  • #4
Well, the current MUST be the same as long as all the components are connected in series, right? That's one of the basic laws of circuit theory; current in=current out.
Hooking up the voltmeter won't change the way the current flows in the circuit, since we can assume that its input impedance is infinite (i.e no current is flowing in the leads going to the voltmeter).
 
  • #5
thanks for such a kind reply
 
  • #6
query regarding four probe method

In four probe method, do we 'have' to mearure the potential drop between the center 2 terminals, or, could we swap the functions of the probes...
Also, can we, (theoreticaly), alter the distances between the probes which measure voltage, instead of all the probes being equidistant, that is...?
 
  • #8
@ Studiot:
I would be referring to the series method... thanks!
 

Related to Advantages of four probe method

What is the four probe method?

The four probe method is an electrical measurement technique used to determine the resistivity or conductivity of a material. It involves applying a current through two outer probes and measuring the voltage drop between two inner probes, allowing for more accurate measurements than traditional two probe methods.

What are the advantages of using the four probe method?

The four probe method eliminates errors caused by contact resistance and allows for precise measurements of electrical properties, even in highly resistive materials. It also minimizes the effects of temperature and sample geometry, making it a more reliable method for determining resistivity.

How does the four probe method compare to other measurement techniques?

Compared to the traditional two probe method, the four probe method yields more accurate results by eliminating the effects of contact resistance. It also outperforms other techniques, such as the Van der Pauw method, in terms of accuracy and reliability.

What types of materials can be measured using the four probe method?

The four probe method is applicable to a wide range of materials, including semiconductors, metals, and insulators. It can also be used to measure the electrical properties of thin films, multilayer structures, and nanomaterials.

Are there any limitations to using the four probe method?

One limitation of the four probe method is that it requires precise positioning of the probes, which can be challenging for small or irregularly shaped samples. It also requires specialized equipment and may not be suitable for in situ measurements.

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