[PLUG] UPS shopping (pure sine ...)

Keith Lofstrom keithl at keithl.com
Sun Dec 31 01:51:40 UTC 2023


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          keithl at keithl.com


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