EEVblog #521 – Picoscope 5000 USB Oscilloscope TeardownPosted on September 18th, 2013 3 comments
An impromptu teardown on the Emona stand at the Electronex trade show, of the Picoscope 5000 flexible resolution USB oscilloscope, with a small crowd of EEVblog viewers watching on.
Also uses the Tagarno HD ZIP 40x digital magnifier.
I remember there was a video that talked about grounding but can’t remember which one so I’ll just ask this here:
How’s it possible that after measuring 0.3V AC and 8 microamps current between my ungrounded computer (Apple aluminum keyboard heater metal), while doing the volt measurement I accidentally touched both the keyboard and the water heating battery (ground), I got shocked so it felt in the heart. Everything I’ve read to date said one needs a bit more volts than 0.3V with 8 microamp to feel a thing.
The reason I started probing was because both a friend and I had noticed that touching my computer case has this gritty feel to it when sliding finger across it with power connected. Same with this new Apple keyboard with alu surface.
Another thing I’m wondering is if connecting the computer ground to the metal exposed at the water heater/battery thermostat could cause galvanic corrosion. The gritty feel is gone with the power supply grounded. I didn’t remember having this gritty feel problem (atleast as noticeably) before upgrading my computers gpu and psu.
I found a thread about Apple’s Shocking keyboards with this link. (though the gritty feel existed on the steel PC case before I got the keyboard and one site suggested that it has to do with ATX psu design. I’m quite sure this gritty feel started after I upgraded the psu and gpu recently)
“Electrovibration, cutaneous sensation of microampere current” Acta Physiol Scand 1983 118: 19-25
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