Re: A stable and repeatable low value capacitance meter
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The example .pdf went AWOL on the first pass!
PeterS???????????? G8EZE
-----Original Message-----
From: swallowp via groups.io <swallowp@...>
To: [email protected]
Sent: Sat, 3 Sep 2022 9:29
Subject: [Test Equipment Design & Construction] A stable and repeatable low value capacitance meter
A while ago I came across a really simple capacitance meter at ?? https://wordpress.codewrite.co.uk/pic/2014/01/21/cap-meter-with-arduino-uno/index.html
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.? It puts the DUT and a reference capacitor in series, applies a DC step voltage and measures the resulting voltage across the reference capacitor.? A? disadvantage is that the DUT is floating, the reference capacitor being the input capacitance of the Arduino.? The article is the start of a thread which has links to notes on resolution and expanding the measuring range.
The original scheme uses a PC to display the results, but it is fairly trivial to add an LCD or OLED to make a small self contained bench meter using an Arduino Pro-Mini module or similar - example attached.? Ditto to add an offset calibration mode to compensate for different test lead capacitances.
I have tried a number of capacitance meter circuits over the years and tested several devices of the AADE/LC100 self-oscillating type, which although they use sound principles and theoretically offer good accuracy, in practice suffer from drift when measuring small values of capacitance (and sometimes huge errors when measuring larger capacitors).? This circuit is both sensitive and stable, even on the plugboard I used to try it out.
Peter S ??? ??? G8EZE
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