I’ve played around with a power supplies in the past and each one seems to have a safety feature preventing electrocution even when touching something which has a current running through it. How does this work? How does the power supply know that’s it’s touching skin as opposed to another conductive material.
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Human skin varies in resistance from about 1kohm (under wet conditions) to 100kohm (under dry conditions). With DC voltage about 5mA is the threshold of sensation and 300-500mA can cause heart fibrillation (AC is much lower 1mA for sensation and 60-100mA for fibrillation). You can still be significantly harmed (internally burned) by current levels below fibrillation levels, you skin may break down under higher voltages decreasing your resistance, you may not have a good idea of your skin resistance, etc. In short DO not go experimenting with this…
Under best (dry) conditions, it would take V = IR = 0.005 * 100E3 = 500V to reach a current that you could feel. It would take V = 0.3 * 100E3 = 30000V to reach fibrillation.
Under wet conditions, it would take V = 0.005*1E3 = 5V for sensation level and V = 0.3 * 1E3 = 300V for fibrillation levels.
Normal benchtop supplies typically max out around 60-100V, but usually well under 50V which is relatively safe. They probably provide a few safety warnings, but do not provide specific protection against electrocution. In short, you should not be messing around with any power supply that can produce significant voltage and current unless you know what you’re doing.
Two common safety procedures that are recommend when dealing with high current/voltage supplies are:
1) Remove ALL jewelry before working. No fun to have you fingers burned because your ring touched two points in the circuit, or your necklace dangles onto something it shouldn’t.
2) Only use one hand when dealing with the circuit. This prevents creating an easy path for the electricity to flow across your heart (your heart is located between your two arms).
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