mmmmmmBacon12345: They aren’t any different. In both cases you’re just establishing a common point to reference voltages against
For AC your signal will vary between above and below ground regularly. For DC your signal will either be above or below ground and stay there
torpedoguy: Unlike a typical household protective earth ground (AC), in a DC circuit, the “ground” is often somewhat of a misapplied but extremely common term for what’s a reference point in the circuit. You’ll notice your multimeter usually says COM where plugging in one of the probes; that’s what it’s for.
Voltage is measured as a *difference* in potential, so you need a 0 to base it from. This is that reference point, and everything else measured-from and returning-to there in the end.
It gets more complicated with AC/DC coupling setups where noise is an issue; in this case AC grounds refer to grounds with a capacitor which blocks the DC signals.
ObserverOfTheNight: For AC, you are actually connecting to an earth ground through a cable or rod. For most low volt DC, you just connect to a reference ground. Think negative battery terminal in a car. In both cases you are just completing the circuit, so current can flow.
TBNecksnapper: The confusion may be between actual ground for safety and the neutral wire, in AC, which should also be at 0 voltage. While DC is usually using calling the neutral as ground, I think this is mainly because DC is low voltage and doesn’t really need the safety ground.
With DC you normally just have your positive voltage wire and then you have ground, which is have you define as 0 volt and measure potential differences against, and wherever your device uses power, it’s doing so by connecting back to the ground to get the voltage difference, *so the consumed current is lead back in the ground wire*. This ground may not even be connected to the earth, DC is usually used low voltage devices which don’t need grounding.
With AC, you have 3 wires, phase, neutral and ground. When you use power you use the potential difference between phase and neutral, *so neutral is what’s leading back the current* (although it’s AC, so it’s not really going in any direction in this case. Ground is not supposed to lead any current at all! **except when something goes wrong**, then it should shortcut the phase so the current it down into the ground instead of into you, this also quickly blow a fuse (or activate the ground fault switch if you’re more modern) to stop the phase altogether.
So basically, ground in DC rather corresponds to neutral in AC, while ground in AC is strictly an added safety wire that has no other functionality. This difference is not really because of AC vs. DC, but rather between high vs low voltage. (I immagine that a high voltage DC device would have a separate ground as well, and a separate neutral which, at the very end may still be connected to the ground)
i_manufacture_drugs: Electricity = angry pixies that want to go home.
AC = angry pixies who want to get back in to the earth (home) we are using the neutral that is bonded, connected, to the earth to get them there.
DC= angry pixies want to get back to the negative terminal (home). Some people say the pixies go from negative to positive but we will ignore them for now. Some times you will have a DC power supply that has the negative terminal bonded to the earth, this is for safety.
In both AC and DC you ground the system to provide a path home for the pixies and that path should be a Low resistance path so it is easier for the protection, fuse/breaker, to trip and stop the pixies.
manInTheWoods: It “grounds” only high frequencies. Probably to removes high frequency noise, but at the same time avoiding ground loops.
If you have two electrical appliances with metal chassis connected with a wire, you normally don’t want a ground current flowing in the cable.
whitcwa: “Ground” has multiple definitions depending on the context.
In AC power it is the protective earth connection. It’s there for safety, and normally carries no current.
In cars or electronics, “ground” is the zero volt reference. It is technically just a very convenient circuit common point. It is not a true ground reference since there is no connection to earth. It is often connected to a metal chassis, but doesn’t have to be. It is often connected to the negative terminal of the power supply, but if the supply has more than one output, it can be an intermediate voltage. So a supply with two outputs could have +12v and +5v with respect to common ground, or it could have +12v and -12v outputs.
TheCowardBobFord: What prompted the question? Was it something you saw/read? Might give us a clue to help answer
hoser89: There really isn’t a difference between AC and DC grounding.
The point of grounding is to create a 0v point of reference for your system
And to create a safe path for fault current to dissipate.
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