I’m live, is this normal or do I have a super power?

Thread Starter

Dogfood61188

Joined Dec 14, 2019
2
Hey guys First post here just joined up because I don’t think I can go any further in electronics until I deal with this... or discover this is normal and I’m testing wrong.

I got a scope recently and have been playing...ah experimenting with it. Something I wanted to do was connect up my electric guitar and see how the wave looks for different notes. As the hairs on my arm brushed against the strings I got a little shock. Just like I always get when my arm touches the metal case of my phone when it’s charging and when my laptop touches the hairs on my stomach. Knowing that my guitar was grounded through the scope something clicked in to place, anything that’s grounded is giving me a shock, but if there grounded then I’m giving them an electric shock, and everything I touch, all the sensitive electronics I touch, the boards and chips that seem To not work when AlI I have done is take them out of the ESD bag must also be getting a jangle off me. If it was static from the cheap nasty pink carpet that came free with the house then why is it constant.
probe in mouth time. I’m getting around 10Vac @50hz (I’m in the Uk so mains is 230rms @50hz). I’m live at 10v... not a chance, Clearly I don’t know how to use a scope. But I definitely know how to use a multimeter... ok I’m live. But surely there’s no current there. Turns out I can run an LED just by licking my fingers and holding one leg against earth it’s dim but it’s definitely lit.
So I probe my mouth on Chanel 1 and the mains on channel 2 see how they compare. The 50hz in my mouth seems to be leading the 50hz mains so I think it’s an induced voltage it seems to vary depending on where I am. My carpet is horrible but not at all conductive. I’m lost, where’s it coming from? how do I get rid of it? Do I need to get rid of it? Health risk? Superpowers? I was hoping for X-ray vision or flight but I guess volt man could work people need LEDs testing right
7AF75BC6-1DE8-4CA3-B7FF-419D35E905C3.jpeg
 

MrChips

Joined Oct 2, 2009
21,112
Welcome to AAC!

Firstly, be aware that we are all being surrounded with 50Hz or 60Hz electromagnetic radiation if you live in just about any location on the planet, unless you are out in the middle of nowhere with no power lines in sight.

Because of this, if you were to touch the tip of a probe connected to an oscilloscope you will pick up this AC mains signal. The human body acts as an antenna.

If your electric guitar pickup and the amplifier is receiving this signal then you should hear a hum coming from the loudspeaker of the amplifier.

You should not be sensing any kind of tingling sensation when you touch your guitar or any electrical equipment or household appliance anywhere. If you do, it is very possible that there is a fault in your house electrical wiring. This requires immediate attention by a qualified trained electrician. Do this promptly since your life and anyone else in your house is at risk.
 

Dodgydave

Joined Jun 22, 2012
9,157
Either your scope isn't Earthed or the guitar amp isn't Earthed correctly, get a multimeter and check the earth connected to the plug to the scope casing..

It's possible that the guitar amp has a switchmode psu..
 

Audioguru again

Joined Oct 21, 2019
1,483
It is winter, the air is cold and dry. Therefore your carpet charges you with static electricity when you walk or shuffle on it.
Then of course you feel a discharge and blow up sensitive electronic parts when you touch an earth ground.
 

Thread Starter

Dogfood61188

Joined Dec 14, 2019
2
Thanks guys. My amp wasn't connected when I was getting the little shock it was just it’s just the pickups of the guitar giving power when I plucked the strings that I was measuring. It was when my arm touched the strings which were earthed through my scope. It isn’t enough to break down my skins resistance but when it touches a hair it has a path below the surface. I have metered from my scopes ground to the radiator in my room and have a good earth and my martindale says my Earth loop impedance is 0Ohm. In the pic the blue trace is the house mains supply and the yellow trace is just my mouth to earth when I’m standing on my insulating carpet. The little shocks I’m getting are when the hair on the inside of my arm touches the grounded case of my phone when it’s on charge. Things like that but I always dismissed it until now assuming it was normal. I’m sure it’s voltage is coming out of me going to earth. Now I have scoped it and seen it’s 50hz ac I’m pretty sure I can rule out static. I think it’s induced in me as though I’m the secondary of a transformer and touching earth is completing the circuit. I’m no expert with the scope but my fluke f117 is a different story and that’s saying 10v@50hz from my mouth to ground so that’s 10vRMS. That’s far more than I would ever have expected.
 

Audioguru again

Joined Oct 21, 2019
1,483
Your body picks up 50Hz or 60Hz electricity because it is all around you and there is capacitance (not inductance) between it and you. You even said that your 'scope shows your pickup leads (is ahead of) the actual electricity. Capacitive coupling leads, induced coupling lags.
 
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