Wrap about 20-30 turns of wire around one leg of the AC power line and connect both sides to a scope and you have an inductive powerline oscilloscope. Much safer than resistors and capacitors.
Also: $32.00 off Amazon: MINIWARE Pocket Oscilloscope DS211, Portable Oscilloscope Mini Size Handheld, Built-in Rechargeable Battery, 1 Channel, 200Khz Bandwidth, Entry Level Oscilloscope for Beginner And it even comes with a probe Ted -----Original Message----- From: PLUG <plug-boun...@lists.pdxlinux.org> On Behalf Of Keith Lofstrom Sent: Saturday, December 30, 2023 5:52 PM To: Chuck Hast <wch...@gmail.com> Cc: Portland Linux/Unix Group <plug@lists.pdxlinux.org> Subject: Re: [PLUG] UPS shopping (pure sine ...) Many laptops have some sort of stereo audio input jack. I can imagine a resistor+capacitor kludge that attenuates the "hot" and "neutral" legs of a power cord down to the stereo input levels. A program on the laptop captures hot and neutral voltage waveforms, differences them, and (somehow) uses the digitized audio signal to characterize the voltage waveform quality produced by the device the cord is plugged into. Perhaps logging the waveforms to disk on the laptop, for long term monitoring. Sub-sampling at 600 samples per second and 16 bit resolution, that is 40 gigabytes per year, more than enough to capture "rare but too-interesting" power glitches over time. If someone wants to write the program to do the differencing and logging, I can put together a few cord-and-resistor-and-stereo-plug kludges, and trade hardware for software. The result would be a portable setup for evaluating the waveforms produced by a UPS in service, or a candidate UPS in the store. Besides evaluating UPS waveforms and behavior, it might also be interesting to look for time correlations in power waveforms between different locations around the Portland area. An office in an industrial area might see subsecond line voltage sags when a nearby factory is arc welding. I can imagine those driving some computer power supplies and UPS units batty. Keith L. -- Keith Lofstrom kei...@keithl.com
