Ground & references
Because voltage is always a difference, every circuit needs an agreed zero point to measure from. That point is called ground: the common 0 V reference that every other voltage in the circuit is compared to. There’s nothing physically special about it. No exotic charge, and no actual connection to soil required. It’s a convention, like using sea level for altitude.
The word covers a few related ideas. Signal ground is the reference node on a board. Earth ground is a literal rod in the dirt, there for mains safety. Chassis ground ties a metal enclosure in. They’re often connected to each other, but not always, and mixing them up causes real trouble in mains-powered equipment.
The classic beginner mistake goes like this: power two boards from separate supplies, run a signal wire between them, and forget the ground wire. Each board measures its “3.3 V” against its own reference, so without a shared ground the signal means nothing and the receiver sees noise. When two circuits talk, their grounds have to be connected.
Key points
- Ground is the agreed 0 V reference point, not a special kind of charge.
- Node voltages on a schematic are all implicitly measured against ground.
- Signal ground, earth ground, and chassis ground are different things that share a name.
- Two circuits exchanging signals need a shared ground, or the signal has no meaning.
Practice
0 of 2 answered · Not startedWrong answers just let you try again, and hints are there if you want them. Answering every question first time, without hints, is what earns mastery.
- 1
What does "ground" actually mean on a schematic?
- 2
Two boards each work alone but misbehave when wired together. What is the first thing to check?
