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| Capacitive & Inductive Impedance Plots with SDS2104X Plus Bode Function |
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| TopQuark:
Cool stuff :-+ Do you mind attaching the Bode plot raw data file so that I can play with the data a bit? |
| mawyatt:
Just measured a 2uF Polypropylene, but data file is too large. Sent a PM note with my email, respond so I can send data file. Here's the 2uF Plot using the Diff Amp Setup with 1K sense R. Cap measures 1.9135uF (-90.00 degrees), and with TH2830 1.9745uF (-89.990 degrees), with IM3536 1.9745uF (-89.999 degrees) at 1KHz. The nice thing about using the Diff Amp approach is most folks will likely have such and no additional probes or equipment necessary. With this Diff Amp approach, we're going to abandon the Transimpedance Amp approach and just work on getting a good setup fixture. We'll add a few more plots hopefully today. Edit: Added a 10nF Polystyrene Type (#47), using 10K (9.96783K) sensing R, and measures 10.857nF (-89.991) with TH2830 & 10.0853nF (-89.996) with IM3536, and computes as 10.074nF (-89.40) at 10KHz from Bode Plot. Best, |
| mawyatt:
Technique works well for inductors also. Here's 470uH Inductor measured with a 100 ohm & 1K sense R. #49 is with 100 Ohms R #51 is with 1K Ohms R Edit: Added #52 which is a 100uH Inductor with 100 ohm sense R. Also later added these: #53 1mH with 100 Ohm R, 1.101mH (measured with TH2830 1.0417mH) #55 2.2mH with 1K R, 2.354mH (measured 2.2816mH) Best, |
| trobbins:
Nice to see those plots and that code is advancing on providing an ideal model representation of the part. With a good soundcard, the REW software in widespread use introduced that impedance plot and part modelling function a year or two ago. The frequency span is obviously limited to the soundcard, so typically circa 2Hz to 96kHz, but can get down to about 0.5Hz. The REW three measurement calibration setup using say a 0.1% resistor was able to better 1% tolerance of reference cap and air-core inductor values that I had back then (I only had circa 0.5% accurate reference parts then and no better calibrated LCR meter). For my audio related projects, the impedance plots contain an extra wealth of insight into DUT operation compared to just the 4 spot frequency measurements from my LCR meter, especially below 100Hz for inductive/transformer parts. Having a component modelling feature, with the ability to automatically use some second order modelling circuits when applicable, and overlaying the modelled response to the measured response is a good goal imho. |
| mawyatt:
Agree that graphs of impedance and other parameters vs. frequency are more useful than the usual "spot frequency measurements of typical LCR meters", especially true when DUT resonances are involved. The quality LCR meters that have built-in plotting capability are quite expensive and likely out of reach for most, and why we took on the endeavor to see if the popular SDS2104X + Bode Function could be coached into providing a decent impedance graphing capability over a useful frequency range with reasonable accuracy. Using an inexpensive Differential Probe that many may have (like the Micsig DP10007), with the DSO provides a useful solution without too much effort. Hopefully Siglent is watching and will consider providing some helpful Bode Plot enhancements which will expand the Bode Function capability for this type usage. Best, |
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