I have experienced extreme levels of EF fields (800-1000) when charging the device from a USB charger. At first I got alarmed because I thought it was the geographic location that had the fields, but the disappeared if I disconnected the charger.
Has anybody has similar experience? If I charge from a powerbank this phenomenon doesn't occur.
Is this explainable in any way? I have a theory that I actually gave the field in the power cables a path directly into the circuit, like an antenna which was interpreted by the device as an external field. Is there anybody qualified (which I am not!) to explain to me what just happened?
When you connect the device to a power supply, what happens is that you place the ground plane of the device at an electrical potential which is that of the power supply ground. The ground plane of the device will therefore generate an additional electrostatic field with its environment which you will see appear on the measurement taken. You can effectively model this by an antenna effect, it's not very far. But it's not the device that no longer works, it's the electrostatic field near the device that changes.
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It's probably the potential that becomes different. It's annoying though, because it's practical to be able to use a charger, but the powerbank solved it also.' Thanks for your reply!