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Some projects and circuits published in Practical Electronics
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2
Volume 54. No. 4
April 2025
ISSN 2632 573X
Editorial
Equivalent Series Resistance testers are very useful
One of our projects this month is the very useful ESR Test Tweezers
tool, a handheld device that can measure capacitance (over a limited
range) but, more importantly, can also accurately measure capacitor
equivalent series resistance (ESR) down to tiny fractions of an ohm.
I was a bit surprised when I looked back over the recent history
of Practical Electronics and couldn’t find much in the way of ESR
testers until our recent LC/ESR Meter from the August 2024 issue.
Given how useful these devices are for repairing and servicing
equipment, I expected other designs to have been published.
For example, Silicon Chip magazine published Bob Parker’s ESR
Meter Mk2 design in its March & April 2004 issues. It turned out
to be an extremely popular project that was made into a kit by both
Dick Smith Electronics and Altronics.
The beauty of an ESR meter is that it can identify faulty electrolytic
capacitors that otherwise seem fine. Electrolytic capacitors are
probably the single most common source of faults in equipment
these days as they have a much shorter lifespan than any other
component, usually measured in thousands of hours.
An electrolytic capacitor might look fine, and a capacitance meter
may even give the expected reading. However, if it has developed
a high ESR (often as a result of the electrolyte drying up or leaking
out), it won’t properly perform its job of filtering or smoothing out
voltages. An ESR meter will immediately detect this and pinpoint
the capacitor(s) that need replacing.
It is not uncommon to find a large electrolytic capacitor that seems
fine on visual inspection and would normally have an ESR figure of
0.01Ω or less, that then measures several ohms! Such a capacitor is
essentially no good for anything other than decoration at that point.
Of course, if a capacitor has a bulging top or a brown stain around
its base, you probably don’t need any test equipment to tell you it
needs replacing. Unfortunately, faults aren’t always that obvious.
That’s why an ESR meter is a worthy addition to a repairer’s toolkit.
Errata
Unfortunately, some errors in the Audio Out column last month
were not spotted before it went to press:
• In Fig.15 on page 24, the 1.5nF capacitor should be 1.5µF
and the 47nF capacitor should be 4.7µF.
• In Fig.22 on page 25, the 2.2nF capacitor should be 2.2µF.
Nicholas Vinen, Electron Publishing (Australia)*
Publisher & Editor,
Practical Electronics Magazine
* a division of Silicon Chip Publications Pty Ltd.
Practical Electronics | April | 2025
