DIY capacitance meter


Electro-Labs created new open source hardware project,  a DIY capacitance meter:

This is a capacitance meter which can measure capacitors rated from picofarads to millifarads. The principle of operation is simple. Just apply voltage to the capacitor and measure the elapsed time to charge it. The circuit is based on Atmega328P and it is Arduino IDE compatible. It includes the voltage regulators which output 5V and 3.3V from 9V input. A Nokia 5110 LCD is used to display the measured information. Thanks to the 4mm banana jacks, various kinds of probes can be used such as SMD probe, crocodile probe etc.

More details at Electro-Labs project page.

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  1. under what circumstances is the 0.01 pF readout resolution justified? I have a cheap ebay C tester with that resolution, but it is never stable at that level, to say nothing of repeatable, and of course not accurate.

    1. Seconded. Also he is doing the demo with a pF SMD capacitor part using SMD chopsticks test leads… It would be nice if he could just stick to 3 digits.
      For a capacitance meter project with some example measurements where the author attempts to test accuracy on a casual basis, see elm-chan’s project, google the following oldie but goodie:
      Digital Capacitance Meter – ELM by ChaN

  2. Low Pf measurements by charge time is not ideal in a little thing like this. Frequency domain techniques are far better and allow for higher source frequencies to scare out parasitic and self resonant effects. The drawback however with frequency domain is the usual requirement of one or more calibrated inductances, not to mention code complexity.

    1. Ha ha, calibrate the inductance… yeah, right. Measurement by charge time is the best hobbyist-simple-circuit method. Superprobe does this too. But I wonder what other method can be done in a simple way? Don’t think there are that many options for hobbyist circuits.
      A capacitance meter is nice to have, but for one I end up never using it for essential tasks. You see, for projects where I use high quality parts, the parts are new and should work within the spec’ed tolerance. So I use a capacitance meter only for checking very old parts or scavenged parts, mostly electrolytics, and those I use in less important boards or prototypes.

      1. While we’re talking about capacitors, I’d say an ESR meter would be orders of magnitude more useful considering that at least 90% of failures in modern electronics are caused by one or more dried-out caps (and they aren’t always visibly busted). Then again of course that whole site is basically a big ad for their own PCB software suite so don’t expect much…

  3. I wonder what makes your expectations high? Isn’t it enough for such a hobby site giving basic information about capacitance measurement, a piece of code which may be helpful for a hobbyist looking for something similar to that, providing a weekend project option, etc.?

    1. Of course it’s a hobby project but for me the general rule is that when a meter provides an output digit, it means something. I suspect that the last digit of this meter is not meaningful, it just provides a distraction as it updates randomly due to noise, and it would be better to have 1 or 2 fewer digits and use a larger font on the LCD screen. Just my opinion.

  4. Max, on the other hand, “component testers” aka “transistor tester” exist on ebay.

    I have bought 181861077271 for about £8 and even in my drunkest state the lcd display is easier to read than decoding color rings with my old dull eyes… Of course results are questionable, but a good guidance anyway.

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