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- since 1996 -

IMG ULTRASUONI SRL
Ultrasonic transducers for industrial applications (NDT) and medical (Doppler effect). Probes, Ultrasonic instruments, Special systems for NDT.

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Technical Discussions
arun kumar
arun kumar
07:37 Dec-11-2002
four point probe resistivity measurement

the following queries are regarding the four point probes used for material detection


can the four point probes be used for thick plates, large drums? if yes what is the level of accuracy? what are the correction factors to be used for differen dimensions?


    
 
 
Sean S. Franklin
Sean S. Franklin
08:31 Dec-11-2002
Re: four point probe resistivity measurement
:
Aarun,

Yes, the four point probe resistivity measurement or the MDT Automation M100A Metal Inspector can be used to measure various thick geometrical samples.

Firstly, probes are identified by the center spacing of the two adjacent pins (pins 2 and 3, two inner most pins). This spacing is measured in inches and converted to thousandths of an inch (mil). Therefore, a probe that has 0.100 (2.54mm) inch spacing between the pins is called a 100 mil probe.

The first consideration in selecting a probe is the type of measurement you plan to make. If the measurement of absolute resistivity is of primary importance, then the probe should be much smaller than the sample size. For relative resistivity measurements, you can choose any probe if you establish a reference resistivity against which measurements can be compared.

Finally, the volume of the sample bound by the probe is important for thickness measurements. Current penetration is approximately one and a half (1-1/2) times the probe pin spacing. For example, the 100 mil probe can be used for applications to a depth of 150 mil, 500 mil probes up to a depth of 750 mil, and so on. The level of accuracy is within +/- 3% without a fixture and 1% with a fixture. The fixture is designed to position and stabilize the probe to the sample surface.

For additional information and literature, please contact Sean Franklin @ 609-716-4088 or Sfranklin@NDTAutomation.com

: the following queries are regarding the four point probes used for material detection
.
:
: can the four point probes be used for thick plates, large drums? if yes what is the level of accuracy? what are the correction factors to be used for differen dimensions?
.



    
 
 

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