On a related note, does anyone know what effect a non-zero ground voltage can have on the sound quality? Thanks.
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True or False:
1)You measured this with ALL your components unplugged
2)The receptacle (where you measured 122-0-0) was on a different circuit (off a diff breaker) from the outlet that measured 122-4-4.
If 1 and 2 are both true, I have no idea why the 4 volt offset is there.
If 1 is false: In some power supplies there are diodes that are connect the chassis to ground in both directions. The chassis could be completing a strange trip back to earth ground and is causing the offset.
If 1 is true and 2 is false seek immediate shelter (just kidding)
Please let me know as much about what was going on that day
Appreciate the article. But if the ground outlet's ground is not connected to anything, should the reading give 0V instead of 4V between hot and ground and between neutral and ground?
Voltages are everywhere...if the ground is connected to a grounding rod (earth) and not to the neutral at the panel then you are simply measuring the voltage between the floating transformer from your utility and "earth" wherever your "earth ground rod" happens to be buried.
This is not a good thing - if you have a lightning storm and it hits the powerlines then these may carry very high voltages into your components within your home as lightning seeks a path to "earth"...in finding a path of least resistance it may burn something - sometimes even several items can get fried!
BTW - since a path to ground via a grounding rod may not be very good - this also bypasses the safety protection on your equipment with three prongs - the idea is that the chassis is both grounded and connected to neutral at the panel which means that in the event of an equipment fault you will not encounter high voltages when you touch a chassis and something else that happens to be grounded.
Imagine my surprise when I found that one of the receptacles measured 122V between hot and neutral, 4V between ground and neutral, and 4V between ground and hot. HOW IS THIS EVEN POSSIBLE? If hot and neutral are 122V apart from each other, they simply cannot both be 4V away from ground, right?You have an open equipment ground.
It could be caused by several things.
* Not made up on the receptacle. Wire may be broken at recept.
*No equipment grounding conductor at the recept rough-in box.
* Open joint at a feed through of another recept rough-in box, or a junction box.
4 Vac reading you are getting? Phantom voltage..... Typical with digital meters.
Connect a load like a 25 watt light bulb in parallel with the meter leads and take a reading....