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How to measure resistivity in ohms/square with a resistance instrument?

Although the PRF-912B Miniature Concentric Ring was designed to work with Prostat resistance meters, it is compatible to work with other meghometers as long as they are able to work BNC adaptor and cable as long as you have a resistance instrument that supplies a constant defined voltage of <10, 10 and 100V (depending on resistance being measured). If this is the case then you could use the PRF-912B with a third party megger.

It is not recommended to use a simple multimeter for making concentric ring measurements through a range of 1ohm – 10kohm, as most multimeters cannot supply a constant voltage output of a defined value.


Also, the readings that you would receive by using the PRF-912B would be reported in ohms, not ohms/sq. To get readings in ohms/square, you would need to calculate this based upon the area of testing and the thickness of the material.  Therefore, please note that there is a very specific difference between resistance and resistivity measurements, with resistivity being defined by:


Commonly, people often use a “rule of ten” to “calculate” resistivity from resistance by taking the resistance measurement and multiplying the result by 10 to give an approximate value, however this is not recommended as it may not be valid for materials that are laminated, plated or metalized with conductive coating/material. This fact should be understood when users utilizing concentric rings are required to satisfy specifications given in ohms/sq.


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