Because it was a one off I cheated and used a 4040, made life way easier.
I dont see any reason why you couldnt dump the frequency into a timer i/p, you could use the capture/compare and timer 1 module on a pic, timer1's good for 50mc's.
I have built one, mine uses the comparator within the '628 so theres less comps.
Its very good and very accurate well worth the bother to build.
I've never used the 13k50, does that device have slew rate control
...it sounds like you know more than me on that front.
Next, no I didn't use the caps to make an LC RF oscillator.
Re the Fluke multimeter inbuilt cap meter, I have a few Fluke meters and the cap meters are not great. It reads within about 5% of the real cap value and are best used as a "cap ok/broken" test.
Part of the problem with a LC type cap meter is the relationship of cap under test to frequency is not linear. I think the formula then needs square roots to determine the cap value (or the L value) from the measured frequency. That takes a lot of processing and will hurt accuracy compared to a nice linear C=period RC osc like in my meter. I would expect my cap meter to outperform that LC meter in measuring capacitance, although of course mine won't measure inductors.
If you want a good LC meter, this link is about the nicest I've seen, and is also available as a kit or just as a programmed PIC. Personally if you want to get into RF I would get his kit as it looks quite well designed and laid out, it is a refinement from his first LC meter so it has been well optimised over time;
http://www.rfcandy.biz/communication/imp_lc.html
That page also covers some of the math required for that LC osc.
...essentially you are counting the elapsed time of the period over and over again(essentially "method 2" in post 3), adding that time up into an accumulator until a certain threshold is exceeded. Then you divide the accumulated by the number of elapsed periods(averaging the result)? Which should essentially be the number of times you have added to the accumulator (times 16 for the prescaler).
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The last part may be getting past me, but I think I generally understand otherwise. The accumulator bit is quite interesting, I hadn't thought of doing anything like that.
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... what I think I would rather do instead is measure the frequency and measure the drift, so I can simultaneously display the average frequency(part value) and the Min/max(tolerance). Hypothetically this will reveal a parts 'Q' factor, as changes in value may appear when the leads are moved, temperature drifts, micro-phonics, and so forth. All very important things to account for when making a realistic radio circuit as I understand.
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(re using the tested caps in RF) That's unfortunate. I would really like to see demonstrated if a low frequency measurement of a cap/inductor faithfully represents it's high frequency value. I just shuffled through my locally saved schematic archives and found the link that I remember reading about HF/LF measurement discrepancy.
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As for accuracy, I don't see how you expect the accuracy to suffer very much. He states that the mathematical accuracy is better than 1% with the 24 bit float routines. Compared to his version, I plan on using the full 32 bit routines plus having larger numbers to work with.
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Not to ruffle your feathers. But that meter is virtually a carbon copy of the meter I linked to in post #1. Yeah, it's details are different, but it's... the... same... meter... Same comparator based parallel oscillator, same maths, about the same MCU.
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