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| Unexpected LCR meter behavior change - dependent on measurement lead positioning |
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| TERRA Operative:
--- Quote from: maelh on January 11, 2024, 10:18:09 am --- --- Quote from: TERRA Operative on January 11, 2024, 04:57:29 am ---Are the leads shielded? If not, it might be worth replacing the test clip cables with thin coax and terminate the meter end of the shield to a banana jack to plug into the guard terminals. --- End quote --- I am unsure if they are shielded, see my post above (manual doesn't specify). I wanted to make a test setup with banana plug cables, but not sure how to attach them correctly and where the guard cable would come into play in this setup. I assume your approach would mean I need to make my own cable out of thin coax and then solder banana plugs onto one end, and aligator clips on the other end? It would become a 2-wire measurement setup only though, so I am not sure it would be compatible with my 4-wire (plus guard cable) LCR meter. --- End quote --- Nah, use four lengths of coax, one coax to each side of each kelvin clip, four banana plugs terminated to each center conductor at the meter end of the cables and then tie the shields together per kelvin clip, using two banana plugs for the shields, one per kelvin clip and plug both in to their respective guard terminals. The shields stay unterminated at the kelvin clip end. Using dual banana plugs for the signal wires would make a neat arrangement less prone to tangling too. |
| chilternview:
Your meter spec says it has an accurary of +/- 1% on its 20uH range at 100kHz. That's 200nH. Although the meter resolution may be 1nH on that range, the last 3 digits are likely to be noise and/or test lead effects. Consider the impedance you're measuring - a 200nH inductor has Z = jwL = 2*pi*1e5*2e-9 = 0.001 ohms. As iMO says, you need to be measuring it at a frequency at least 2 orders of magnitude greater, using something like a VNA. |
| maelh:
Thanks all for your insightful replies. I actually do have a NanoVNA and was trying to validate the measurements of the LCR against the VNA. Another issue is that when using Kelvin leads to measure, you can put a coil into plated throughholes, then attach the ends of a coil to a meter, and fine tune it the coil (by squishing/expanding it). With the NanoVNA you need to keep it in the test fixture, and cannot measure it in the final board. |
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