Electronics > Metrology

Fluke meter lightning bolt? Dangerous?


my meter shows the lightning bolt (dangerous voltage present).   I was troubleshooting a Bass Amplifier which had 30v rails and the bolt appeared.  I work on tube amps usually having a B+ supply in excess of 400 vDC.  I guess I am not being careful enough aroubd solid state amps. is 30vDC in a solid state bass amp deadly?

Many audio amps use dual supply. A single 30 V supply is usually safe, though in principle can become dangerous when really wet.
It it's a dual +-30 V supply you should be more careful - that's about the legal limit from which on DC voltages are considered dangerous. So don't tough things on purpose, but not yet really dangerous - as long as you only touch one side.

There are solid state amps with higher voltages (e.g. +- 60 V) too, if this is high power.

The warning of the meter might come early, just in case, especially if it is AC voltage present at higher frequencies.

The general rule is when you get over 24VAC, or maybe 30VDC, you should start worrying about shocking yourself. This is based on how much current might pass through you body under worst conditions at this voltage. These are guidelines, nothing more. A 9V battery might kill you if you puncture your skin and pass the current from one hand to the other. Perfeclty dry and thick skin hands might be able to withstand 220VAC without killing you. It all depends.

If a Fluke meter shows a danger symbol. it is best to start thinking about how you managing your safety. Nobody died from not touching the wrong thing.


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