I have APC's surge protector and it can, according to the manufacturer, detect if power socket is earthed.How reliable are these detectors?
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\$\begingroup\$ Include a link to the actual product. What would be needed to detect a proper earth connection ? I would say: Stick a long metal pin in the earth, ideally connecting to ground water level and measure the resistance between the earth you just made and the one from the socket. Does this product do that ? Nope. Then how can it ever detect a "proper" earth connection. The whole concept of surge protectors is moot anyway, most sensitive equipment has some overvoltage protection/mains filtering build-in already. Surge protectors are useless when it really matters like a lightning strike. \$\endgroup\$– BimpelrekkieCommented Sep 7, 2017 at 8:40
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\$\begingroup\$ Here's the link If earthing doesn't work then can the equipment even be protected (lets say a PC power supply, they have many protections but are they useless without earthing?). \$\endgroup\$– user3711671Commented Sep 7, 2017 at 8:42
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\$\begingroup\$ What the SP can do is block voltage spikes from the mains. Like 240 V briefly become 300V. Which does not happen a lot. Also that's pretty useless as a PC's power supply will have a similar filter build-in that does the same. That protection is more a "psycholigical" protection (I paid good money for this so now I'm safe) than that it actually protects anything. I do not know of any examples where such a device actually protected anything and prevented the other device from damage. This can only be tested in a lab with special equipment so it is difficult to do and verify the claims. \$\endgroup\$– BimpelrekkieCommented Sep 7, 2017 at 8:50
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\$\begingroup\$ It might protect something like monitors, right?Could something like PC PSU's protections be useful if it isn't grounded?As far as I know they should cut the power in case of external surges so earthing doesn't seem to play any role here, but what if the PSU itself causes a surge? \$\endgroup\$– user3711671Commented Sep 7, 2017 at 9:00
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1\$\begingroup\$ Grounding is only needed to protect humans. If there's 240 V AC on a PC's metal case, the PC does not care. But humans do. So connecting the case to ground forces the case to be 0 V and safe. It is OK not to ground in case the floor has sufficient isolation. So in a bathroom/kitchen grounding is a must. In bedroom or office: grounding is not compulsory. The spurious signals are not "send to ground" ever, even when grounding is present. These signals are just blocked and stay inside the device. Signals travel in loops so feeding it to ground (one way) is impossible. \$\endgroup\$– BimpelrekkieCommented Sep 7, 2017 at 9:28
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The most likely method of checking the grounding is to pass a very small current from live (hot) to ground, while monitoring the voltage. At it's simplest, this could be an LED or neon lamp, with a very high series resistor, connected from live to ground.
If the measured voltage is very close to the line voltage, the ground is probably good. If the voltage is close to zero, there's probably no connection to ground. If it's about half the line voltage, then you're most likely detecting leakages through capacitors (for instance the filter capacitors in power supplied), and the ground is still unconnected.
