Not sure what his particular application is, but for the benefit of others reading this thread, many manufacturers test and specify inductors in this range (1 uH to 100 uH and beyond @ 100 kHz) for use in power conversion and switching power supplies, which typically operate between 50 and 250 kHz. Examples: Buck and boost converters, noise filters, etc. Why you think this frequency would be unusual for an inductor? Even in an audio application, while the lower frequency range below 20 kHz is more of interest (such a loudspeaker crossover networks and filters), someone "might" want to understand frequency response characteristics of components across the audio spectrum and beyond. Then again, the application may be entirely something else. But considering that Agilent makes a range of precision LCR meters (e.g. E4980A and E45980AL), these cover that spectrum of interest from DC to 2 MHz and the U1733C goes to 100 kHz. I have one and find it to be a handy portable unit for a quick component check at various frequencies.
For the benefit of others reading this thread, I will say that high quality measurements with an LCR which comes with just two alligator clips as standard test leads, is not possible.
Regarding U1733C, I have review this meter and it has issues at 100kHz, it looks unable to zero-out up to the last digit after a complete self-calibration cycle. I though that Agilent will deal with that by an updated firmware, but they did nothing, possibly because this is design limitation than software bug.
My original though was that I can possibly save the day of the one who started this topic, by offering an advice if he was using a wrong test method for a specific component.
And regarding meters at the price range of U1733C, I would say that DE-5000 portable LCR is a much more successful over all design up to 100kHz.
Hmm. Interesting about the 100 kHz issue. I'll have to see if I notice anything unusual at that frequency. That said, I found a somewhat cryptic reference in the firmware revision history that says something about improved measurement at 100 kHz, but that was a couple of years ago -- and it may not be related to the same 100 kHz measurement issue on this thread. For reference, see: http://www.home.agilent.com/upload/cmc_upload/All/U173xC_release_note.txt where it states, "Improve impedance measurement at 100kHz, 100kohm" (from release 0.24 onward).
Do you have a U1733C still or do you recall what version of firmware it was that you tested? I'll need to check my version to compare as well. My unit is relatively newer, so the firmware may be more current.
The initial question was asking why when measuring a 1 uH at 100 kHz does the Q value jump around?
To make a quick 1 uH choke using readily available parts, I needed to combine two short copper wires, each with a ferrite bead in parallel. I used that old thin solid copper telephone wire, something like #24 solid. I twisted the joined ends together and separated the two halves a bit.
I got a nice solid reading of 1.11 something uH, nice averaging, all is good. I did notice the Q value was varying a bit. However, the Q value did not look correct.
I got out a micro-ohmmeter and measured my series DC R for the combined paths at about 3 milliohms. And, therein lies the answer.
If I recall correctly, Q is 2pifL/R. It is simply not reasonable to expect this otherwise beautiful low cost instrument to be able to handle 3 milliohms with two leads (a somewhat difficult measurement in and of itself). It is not always the case that, for a given accuracy, four wires are needed. However, a 4 wire Kelvin measurement is absolutely needed by several milliohms for a stable and meaningful Q reading in this case.
Beyond needing to measure milliohms for Q in this instance, 1 uH is already at the edge of the instruments operating envelope. 1 uH is below 10% bottom scale on the lowest 20 uH scale. Yet, the U1733C had no problem at all producing an accurate and stable 1 uH L measurement to 3 1/2 digits or so at 100 kHz.
I used it some years back for 10 to 30 mH air core inductors with series R on the order of a few ohms to less than 10 ohms with great success. I am very pleased with the performance of the U1733C and highly recommend it. Clearly, it will not match the performance of a $5k+ bench unit with four wire inputs. However, for many lab and field measurements, 3 1/2 digits is plenty good enough.
When it comes down to expectations, low ESR capacitors is the major application. Therefore one meter with stability issues at 100kHz, and with a display resolution which require from the user to add 40 counts in low ohm measurements, does not look as treasure to me.
Agilent needs to redesign this LCR model so to become a solid performer in all supported frequency ranges.
What is the stability issue at 100 kHz? The 1 uH L reading was solid and correct.
The Q reading at 3 milliOhms series R makes no sense from an electrical engineering perspective. In fact, it might be good that it does not average a nonsense reading. There is nothing to fix, the Q reading is not workable for this scenario.
Or which is the smart *** who told you to do that?