why would you have the amp on and passing signal while your source device is stating up....???
yes there's a noise problem which is hard to resolve but that it's a ground loop is totally erroneous.
jitter
if when you touch the metal case the noises (a 60 Hz peak with its multiples) in REW are reduced grounding will be a good solution. I think the noisy measurement in REW or other software is due to this inductive voltage or as you said a leakage current. The problem gets worse when the leakage flux of a power supply with a transformer is coupled with the PC power supply. Is it logical to reduce it with a magnetic shield? Watch this video, please. a magnetic shield seems to have a very noticeable effect on removing the noises.
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Mu metal is a good shielding material although it wasn't introduced in this video. It seems that this transformer uses Mu metal as a shield.
https://www.jensen-transformers.com/transformers/line-input/
In summary, I think combination of a good grounding and shielding comes to removing all the noises.
Inductive to what? Your body isn't inductive.
IMHO those leakage currents are highly likely capacitive currents from the CY-caps to earth of an input filter which a PC PSU or wall wart should have (but probably not as elaborate as the example below).
And at 1 nF they have a capacitive reactance @ 60 Hz of 1/(2*πf*C) = 1/(2π*60*1n) = 2.7 MΩ resulting in a current of 45 µA @ 120 V.
You might try to shield that wall wart, but my guess is that it will not make much of a difference, maybe even no difference at all.
IMHO those leakage currents are highly likely capacitive currents from the CY-caps to earth of an input filter which a PC PSU or wall wart should have (but probably not as elaborate as the example below).
And at 1 nF they have a capacitive reactance @ 60 Hz of 1/(2*πf*C) = 1/(2π*60*1n) = 2.7 MΩ resulting in a current of 45 µA @ 120 V.
You might try to shield that wall wart, but my guess is that it will not make much of a difference, maybe even no difference at all.
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jitter
If you have a transformer connect one of the probs of your multimeter to its metal core and another to your hand (disconnect the ground wire). Measure the voltage. It is a pure inductive voltage that your body absorbs.
You could connect your simple RCA connector to an inductor and move it closer to the transformer. you will see the noises will be increased.
This is where I keep disagreeing. It is not inductive. In case of leakage between windings and core of a transformer, that too is capacitive (albeit parasitic).
Please try the shielding and find out for yourself.
Please try the shielding and find out for yourself.
There's a linquistic problem here - there is electrostatic induction (related to capacitance), as well as electromagnetic induction. Nowadays the former is hardly ever mentioned, but both were named after observing an "induced" charge or voltage.
Note that a human body often acts as a 100 to 200 pF capacitor to Planet Earth.
So holding one lead of a high impedance modern Digital Multi Meter and measuring something that is not at Planet Earth's potential will show a voltage.
Also measuring between a wire that is not connected at either end and Safety Ground/Protective will show what electricians call a Phantom Voltage.
So holding one lead of a high impedance modern Digital Multi Meter and measuring something that is not at Planet Earth's potential will show a voltage.
Also measuring between a wire that is not connected at either end and Safety Ground/Protective will show what electricians call a Phantom Voltage.
Speedskater
How do you explain induced flux near high-voltage electricity? (voltages over twenty kilovolts). Even getting close to these wires is a risk of death. Do you say that is due to the capacitance property of our body, that we receive voltage?
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I don't think that has anything to do with flux but with the fact that a dielectrcum has limits to what voltage differential (potential) it can withstand.
Air is a dielectricum that can withstand about 1 kV per mm of distance, but there are degrading factors like moisture, so in practice we must take a safety margin of 1 cm (10 mm) per kV into account.
If you get too close to (e.g.) a 20 kV source then the conductive properties of your body may create a path for an arc to form because the air ionizes and all of a sudden becomes a good conductor.
Air is a dielectricum that can withstand about 1 kV per mm of distance, but there are degrading factors like moisture, so in practice we must take a safety margin of 1 cm (10 mm) per kV into account.
If you get too close to (e.g.) a 20 kV source then the conductive properties of your body may create a path for an arc to form because the air ionizes and all of a sudden becomes a good conductor.
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Yes, and it's why there are testers and DMMs that can apply a load to identify if you're dealing with a phantom voltage.
The 36 V I measured on my laptop drops to a mere 1.5 V when I measure it with my Agilent U1232A in LowZ mode. At work I use a Benning Duspol that can load the circuit up to 550 mA @ 1000 V.
You mean a capacitive coupling flows a current in the RC circuits and makes a voltage? I mean the voltage between our body and a small transformer core.
What I meant is that the body is some sort of conductor that a high enough voltage can form an arc to should you get close enough to the conductor with the high voltage (when the earth connection is left floating). This breaks down the dielectricum, ionizes the air and strikes an arc between it and you. This has nothing to do with a transformer core. You have to become part of the circuit, though, so this would happen in a situation in which the source is connected at one side to earth, which is normally the case with mains power.
The current "leaked" by the CY caps in the mains filter part of the power adapter is what creates the voltage through a high impedance part that is you AND the multimeter. At 10 MΩ this tiny current creates an impressive looking voltage (U = I * R) but when you lower the impedance in a LowZ meter (something like 1 kΩ) then the voltage collapses.
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