In the answer by Reroute (thank you, Reroute!), he references a very active 253 page EEVblog topic -- $20 LCR ESR Transistor checker project that probably includes exactly what I am seeking. I googled upgrade accuracy precision in the blog, and it looks like this information exists. If any of you electrical engineers have found out an answer to this quesion because you've worked on this actual open source project, I sure would like to hear it. Examples of found text that looks like this is a real question and answerable are below:

...the more accurate the resistor, the more accurate the calibration.

upgrade to a 0.1% voltage regulator if you want accuracy

I will accept any answer where you have specifically been active on this referenced blog, or this open source project, and tried out something and it improved the precision of any readings.

Lacking someone with actual experience with this actual (or derivative) project, I will eventually accept an answer done by research alone.

Awhile ago I purchased one of these kits and then fried it by adding one too many AA's in an attempt to replace the 9-volt so the battery would last longer:

Transistor tester at link above

I just bought another one because I liked it so much, and was hoping to change a voltage reference / regulator and/or change out some resistors or other components for more accurate ones. A friend of mine told me this is an open source project, but no documentation came with this product, and I couldn't find it. I think this is some kind of Arduino, and there is a seemingly infinite body of knowledge to search as soon as you type in "Arduino". Does anybody know how to modify this to improve it? In particular, I am interested in a relatively inexpensive inductance + ESR tester for my students for some classes I am planning. I want something they can use, and I would like to give them decent quality. (If you know something better and affordable by hobbyists/kids/students, please also let me know). Thanks ahead of time. Below is the circuit board itself (again, from the link given earlier):

Picture of a nice, unpopulated circuit board with component values listed.

  • \$\begingroup\$ how many cells did you connect when the device fried? \$\endgroup\$
    – jsotola
    Commented Jun 28, 2020 at 0:03
  • \$\begingroup\$ I pretty much doubt a beta of 294, and you can only get more accurate results on that if you use a collector current that is at least 25% of the maximum allowed. \$\endgroup\$
    – Janka
    Commented Jun 28, 2020 at 0:23
  • \$\begingroup\$ It could be a 2N5087 . The accuracy is adequate for hFE \$\endgroup\$ Commented Jun 28, 2020 at 1:10
  • \$\begingroup\$ Questions on stack exchange sites must be specifically answearble. It sounds like you want instead to have the sort of discussion for which a traditional Internet discussion or user forum is intended, but this site is very intentionally not a discussion forum but something uniquely else. \$\endgroup\$ Commented Jun 28, 2020 at 2:13
  • 1
    \$\begingroup\$ It uses a TL431 for a Vref, so more accurate resistors is a low cost option. \$\endgroup\$
    – user105652
    Commented Jun 28, 2020 at 3:43

1 Answer 1


The project it is based apon "$20 LCR Transistor tester" is open, but people then took that design and modified it to suit there own end goals


Main improvement on these is to replace the resistors with lower tolerance ones, e.g. 1% or better, as that is where most of the errors come from,

  • \$\begingroup\$ Yes, but I would like a specific example from an electrical engineer that has already tried and verified this (if possible) -- see my edit of the question that clarifies what answer would be acceptable in the light of this new source of information. Thank you for your answer. +1 for the link! With that 253 page topic on EEVblog, surely someone here has checked this out and tried to improve it. (I hope) \$\endgroup\$ Commented Jun 28, 2020 at 13:31
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    \$\begingroup\$ One of the people that have tried it would be myself, that is why I immediately knew about it. for capacitance, ESR and transistor beta, they all directly rely on the tolerance of the resistance to determine an accurate reading, the calibration routine where you short out the 3 leads mainly removes the micro-controllers contributions, but struggles with mismatches between the 3 channels passive components. The people who designed the first version and firmware are contactable through there. \$\endgroup\$
    – Reroute
    Commented Jun 28, 2020 at 13:37
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    \$\begingroup\$ here is the exact post from the projects creator eevblog.com/forum/testgear/… \$\endgroup\$
    – Reroute
    Commented Jun 28, 2020 at 13:41
  • \$\begingroup\$ So did you use better tolerance resistors? Or a better tolerance regulator? \$\endgroup\$ Commented Jun 28, 2020 at 15:28
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    \$\begingroup\$ I used better resistors and updated the firmware to the correct regulator voltage. You may not have the firmware option. As ut may be a custom varient. \$\endgroup\$
    – Reroute
    Commented Jun 28, 2020 at 20:31

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