You just need to be careful using one on a 2 wire system. It can OK a deadly situation. If you have a reversal of neutral and the ungrounded conductor, then someone uses the "neutral" as the ground, the tester will be happy but the user won't when they get electrocuted.
Those tester will probably show if the ground is good. But the tester uses a very small current for the test, and will indicate good if there is a high resistance in the ground path, like 100 ohms. A ground path with 100 ohms resistance is useless. A more reliable test would be connecting a 200W light bulb from hot to ground. I have a tester that tests with a relatively high current pulses. I think from a previous thread you have a similar tester.
The testers will also not catch problems that should be very rare, like if some idiot connects the ground contact to the neutral and an idiot has reversed hot and neutral. A non-contact voltage tester can be used to determine if hot is actually hot and neutral and ground are not.
IMHO it is useful to know the limitations of test equipment.
They do make better testers that will look for a resistance between <1 ohm and some smaller amount. They verify a reasonable grounding impedance and will also detect a neutral connected to the ground by the fact that the resistance is virtually zero. Ecos makes the one I have.
The one I have is also an old Ecos. I haven't had it out in years.
A GFCI will trip on a N-G short downstream. It is a feature that was added many years ago. There is a second current transformer that tries to inject a small current on the H and N. It is only possible if there is a N-G short (or reverse wired H-N and a H (which is now N)-G short.
The plug in testers do detect reversed hot and neutral.
On Wed, 10 Feb 2021 19:17:02 -0500, snipped-for-privacy@aol.com posted for all of us to digest...
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