I need to measure electrical conductivity of polymer based nanocomposites using four probe method. To do this, i need to measure current and corresponding voltage drop. The current and voltage readings are not stable. In the attached digram inner probes are volatge while rest are currennt probes.Any suggestions will be helpful to get a stable reading.
Hello Imran,
I don't really understand the diagram you have currently uploaded. You may wish to annotate.
So many questions... What test equipment are you using (simple SMU or a semiconductor analyser)? What configuration are you using?(4T or S-2T)? What sort of values are you measuring (i.e. noise of attoamps is expected even in a very well tuned system). Are you using a Faraday cage? Is the humidity well controlled? Cabling can be a big source of errors, so ensure that there are no defects, if you want very accurate measurements be aware that material mismatch in the cabling connections can also lead to error.
Another simple step is to try and integrate over a longer period of time. Often these are related to the power line cycles (PLC). See this link for more information: http://www.keysight.com/main/editorial.jspx?cc=GB&lc=eng&ckey=710001-1-eng&nid=-11143.0.00&id=710001-1-eng
Your probes- are the needles of good quality? Are you making good, reliable contact with the device? Do you have a good low-resistance ohmic contact between the needle and the DUT?
If you can desrcibe your setup in a little more detail I am sure that it will be easier for myself and others to provide a more refined answer.
I have also attached some good resources from Keysight that may cover some additional points.
Hope you manage to solve the issue,
Jules
The stability depends on the factors as explained by Hammond. Establish good contact with sample by using silver paint at the tip of probe needle. EMI shielding is required. You can place your set up in metal surrounded cage/pot etc. Dehumidified chamber will be ideal.
Dear Jules Lloyd Hammond and Asit Baran Samui......bundle of thanks for quick response..... and now the problem description.
I did use digital multimeter to measure current (I) and corresponding voltage drop using four probe technic. Its a manual set-up. I dont really need to record current reading if suppying a constant current but as the amount of current is limited by material so be more precise measuring current as well. I observed a gradual decrease in current and voltage readings which should be stable to record them. The conductivity can be calculated using the formula
E. Conductivity = (I/ V). (L / w.t)
Where I, V, L, w and t is electric current ,voltage drop, length, width and thickness of sample. I use this formula because of its simplicity as the probes are not really needle probes but like a line probes to have higher probability of contact with sample. I record data with some programme and if i just calculate resistance its not much vary.
The readings are stable for trial resistance (known resistance) but not for composite materials. Another thing , For higher filler loading, readings are somehow stable and fluctuations smeems for low concentration samples.
Jules Lloyd Hammond.... yes, you are right, humidity somehow affects but , can it be really controlable, i mean temperature gradient w.r.t "time"?
PLease, do not confuse with rest of assembly (metallic copper parts)
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