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Hi all,,,,I'm looking for some help or information on what a good ''Q'' is when winding DIY PI Monocoils and also how to measure it? I bought a new reliable (and accurate,,,so they say?)DER-5000 LCR Meter because the other 3 that I have all give different readings. This DER-5000 measures 'Q' as well but I'm at a loss to what it 'Q' actually is when talking Detector coils. Any help on this will be much appreciated,,,Thanks in advance,,Regards, Marty.
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Q is the same for any inductor:Originally posted by MartyJ1963 View Post
https://en.wikipedia.org/wiki/Inductor#Q_factor -
Hi Waltr,,,Thanks,,,I visited the link and gave it a read,,I'm still finding it difficult to understand exactly what it means. I built a coil tonight for my Mirage,,just as a tester,,with 0.5mm copper enamelled wire,,it measured 303.6uh at 2.16 Ohms with a Q of 89.7,,,but I don't really know if that 'Q' is good, bad etc?,,,I only used copper enamelled as a quick tester for my new LCR Meter as I usually use 0.5mm 16 strand 600v PTFE wire for my PI Coils. All my other 3 LCR Meters must've been way out cos' they measured this coil at 400 - 440uh. The new meter has a range of frequencies at which you can test coils, capacitors and resistors at,,,I tested my coil at 100khz frequncy,,is that the correct frequency?,,It tests at 1khz/10khz/100khz/100hz and 120hz. Thanks,,Marty.Comment
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First, I like the DER-5000, I have one and find it to be good quality.Originally posted by MartyJ1963 View Post
Second, I don't find much use for knowing the Q of a coil. I'd rather know the inductance and resistance. Q relies on frequency whereas L & R do not. Your measurement, though, looks spot-on:
Q = 2*PI*f*L/R = (6.28 )*100,000*303.6u/2.16 = 88.31.
If you measure the Q at 10kHz then you should see ~8.9.
If you measure the Q at 1kHz then you should see ~0.9.
Specifying the Q of a coil without specifying the frequency is meaningless. And if you know L & R, you can calculate the Q for any frequency. Which is why I'd rather know L & R.Comment
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@Carl,,,Thank you kindly for your help with my query,,,I'm begining to understand it a little better now and it's great learning all these new intriguing things. I really like this DER 5000 and like you say they seem really accurate. I wound 3 coils, a few months ago, for my Mirage,,when I checked them all today I found that they were between 100uh and 140uh higher than the 300uh I 'Thought' I'd wound!,,,The 0.5mm copper enamelled wire 300uh coil I made earlier this evening worked far better than those 3 coils,,,so now tomorrow, I can confidently start 3 new coils, with better wire, that should be more in spec wth the new Meter. Thanks agan for the explanation about 'Q',,much appreciated. Regards,,Marty.Comment
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https://www.110volt.ru/sites/pdf/TH2821.pdf
These can be used to measure Q at 100Hz, 120Hz, 1kHz and 10kHz.Comment
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I'm at a loss to what it 'Q' actually
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Q is some kinda 'quality of coil' or 'ability of coil to work on high frequency good' or 'ability to work of coil on frequency without
of big losses or with optimal value of losses'.
ie that has a sense if you do what we call 'fastest coil'.
for certainly Foster's 'wow! gotta 5us first delay' issue we know good. if not... then no sense to measure Q.Comment
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Thanks everyone for the replies,,,that's what I love about this forum. I did the 'Upgrade' to the DER 5000 TL-21 accessory and replaced the very short, small alligator clips with some Kelvin clips,,,it's a whole lot easier now to measure coils during building. Thanks again all, Regards,Marty.Comment
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Q Factor plays a big role in VLF IB coils, with its design parameters for off resonance and temp stability etc. It also is related to the frequency response or Bandwidth of such coils. With VLF IB coils, it is quite obvious that the frequency of resonance and Q play an important role in the sensitivity and phasing of such coils (Tx and RX)
With PI monocoil, the relationship between Q and what constitutes a "fast coil" is not so obvious. The SRF in general gives a better indication of parasitic capacitance, and therefore an overall sense of how good the coil will perform in the case of short sampling delays.
I suppose with a little mathematics gymnastics, tables and plots can be developed to give some relevance to Q with respect to PI coils, especially a Transmit/Recieve type of arrangement(two seperate concentric coils).
All the formulae being related.Comment
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