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Comment by spongeb00b | Hacker News Reader

Ok so this literally happens to me! There’s a desk behind my back. When the guy there stands up, roughly 10% of the time my Dell monitor will go blank and reset.

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Seems like this is a relatively common bug. Some months ago, in the HN thread for a blog post by the Lunar app developer and weird bugs people sent him, a commenters posts how this is a known bug and, for example, it's in DisplayLink's support database, and they even suggest some fixes:

"Surprisingly, we have also seen this issue connected to gas lift office chairs. When people stand or sit on gas lift chairs, they can generate an EMI spike which is picked up on the video cables, causing a loss of sync. If you have users complaining about displays randomly flickering it could actually be connected to people sitting on gas lift chairs. Again swapping video cables, especially for ones with magnetic ferrite ring on the cable, can eliminate this problem. There is even a white paper about this issue."

HN Thread: https://news.ycombinator.com/item?id=32631017

DisplayLink support: https://support.displaylink.com/knowledgebase/articles/73861...

Lunar app bugs: https://notes.alinpanaitiu.com/Weird%20monitor%20bugs

Edit: Looking around I've found this funny/interesting short paper from 1999 called "Unusual Forms of ESD and Their Effects". They refer to a Japanese paper already in 1993 pointing to chairs ESD disruption, and also to using a ziplock bag with a bunch of coins to test ESD protection...

Short and interesting! : https://www.emcesd.com/pdf/uesd99-w.pdf

Edit 2: Interesting 2006 research about one of the researchers for the 93 paper:

"ESD noise radiated from walkers was observed in the 5-GHz-band to study the influence on the quality degradation of radio communication. We determined that the radiated ESD noise in the 5-Gk-band is originated by "Collision ESD" and "Induced ESD" when people walk while wearing metal objects."

https://ieeexplore.ieee.org/document/5256785

So, out of curiosity, how do you think the signal was taken in from the antenna in that paper?

I would like to do EM scans around my house just out of curiosity, and the graph is nice.

Is this an application for a cheap usb software defined radio, or is this the output of a several hundred dollar oscilloscope?

My EMI knowledge is almost zero, but I think you can see a couple of examples and projects with interesting information (and cheaper options) about it here in the RTL SDR blog with the 'emi' tag: https://www.rtl-sdr.com/tag/emi/

In fact I'm going to read it later

When someone stands up from an office chair, they also create the ideal conditions for static electricity. If the air is fairly dry, and they have sat and squirmed in that chair for a while, then they will have built up a little bit of charge. However, their body and the seat of the chair act as a capacitor, as they are effectively two objects (plates, in a capacitor) separated by an insulator. So, as they stand up and the distance between the two "plates" increases, the capacitance decreases, but since the charge held remains constant, the voltage must correspondingly increase.

It can be a neat trick to stand up from an office chair and then point your finger at your co-worker's ear.

It's also one reason why I am extra-super-careful to ground myself when digging around the guts of any computer systems when I'm sitting on an office chair.

Haha. Our team has about 10 or so "talking buttons" with sounds of various crassness recorded on them for comedic relief. On a particularly dry day someone noticed that static electricity does not only mess with half of the monitors, but spontaneously triggers a random button.

We found that when one of our engineers sat down on a chair which triggered a button with an obscenely wet fart sound.

Needless to say, our productivity went through the roof that day.

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