3 ms·

Thank you very much for the elaboration. > ...the voltage at the top of the thermistor is always 5 volts, and the voltage at the bottom is always zero by defin

Thank you very much for the elaboration. > ...the voltage at the top of the thermistor is always 5 volts, and the voltage at the bottom is always zero by definition. (Because we're defining it as ground -- ground means "the point which we define as zero voltage in this diagram", although sometimes it also means "a point which we literally attach to the earth" -- darned EEs with their crazy terminology!) Isn't what you're referring to rather a "common" than a ground?

blackguardx 18y ago
Technically that is true, but any common reference point is usually referred to as a ground. If it does indeed connect to the earth, then it is usually called an earth ground.
- mechanical_fish 18y ago
  Yeah, in an ideal world we would all use "common" for the one concept and "ground" or "earth ground" for the other. But in practice we use "ground" to mean "common" and "earth ground" to mean "earth ground". I remember, when I was a beginner, being completely confused about what all those ground symbols meant. That was one of my first big stumbling blocks in electronics. The answer is that they're usually nothing but notational: They save you drawing some wires (every ground symbol is assumed to be attached directly to every other ground symbol by a very-low-resistance wire [1]) and more importantly they define your reference voltage (once you've drawn a ground, you can say things like "this point in the circuit is at 3.2 volts", instead of "this point in the circuit is at 3.2 volts relative to Point X".) --- [1] There are times when the connections from ground to ground have too high a resistance, or when you pour so much current into ground that the ground-lead resistance can't be ignored anymore. Those are called ground loops, and are topics for advanced class. I have a nasty ground loop when I connect my stereo system to my cable TV. It manifests as the sixty-hertz hum from hell. http://en.wikipedia.org/wiki/Ground_loop_(electricity) http://en.wikipedia.org/wiki/Ground_loop_(electricity)

blackguardx 18y ago

Technically that is true, but any common reference point is usually referred to as a ground. If it does indeed connect to the earth, then it is usually called an earth ground.

mechanical_fish 18y ago
Yeah, in an ideal world we would all use "common" for the one concept and "ground" or "earth ground" for the other. But in practice we use "ground" to mean "common" and "earth ground" to mean "earth ground". I remember, when I was a beginner, being completely confused about what all those ground symbols meant. That was one of my first big stumbling blocks in electronics. The answer is that they're usually nothing but notational: They save you drawing some wires (every ground symbol is assumed to be attached directly to every other ground symbol by a very-low-resistance wire [1]) and more importantly they define your reference voltage (once you've drawn a ground, you can say things like "this point in the circuit is at 3.2 volts", instead of "this point in the circuit is at 3.2 volts relative to Point X".) --- [1] There are times when the connections from ground to ground have too high a resistance, or when you pour so much current into ground that the ground-lead resistance can't be ignored anymore. Those are called ground loops, and are topics for advanced class. I have a nasty ground loop when I connect my stereo system to my cable TV. It manifests as the sixty-hertz hum from hell. http://en.wikipedia.org/wiki/Ground_loop_(electricity) http://en.wikipedia.org/wiki/Ground_loop_(electricity)