More of a rant, this, but...
One thing that continuously bugs me is how people refer to "negative ground" or "positive ground". Ground is a reference point for zero volts, to my mind. You can't get negative zero, or positive zero. It's zero.
A better term to use would be plus nine volts, or minus nine volts. Totally accurate.
Yes, you're right.
I think what is meant by "positive ground" is that the ground state is more positive than the supply voltage (which is negative). I might be wrong about that, but it makes sense to my non-engineer brain. :)
Also, it's a legacy term. Effect pedals are traditionally battery powered, and the only way to get -9v out of a 9v battery is to connect the positive terminal to ground.
Quote from: Mike B. on October 26, 2013, 01:00:26 AM
Also, it's a legacy term. Effect pedals are traditionally battery powered, and the only way to get -9v out of a 9v battery is to connect the positive terminal to ground.
Yeah, you're probably a lot more correct about the term than me. That makes a lot of sense.
Quote from: alanp on October 25, 2013, 11:25:35 PM
More of a rant, this, but...
One thing that continuously bugs me is how people refer to "negative ground" or "positive ground". Ground is a reference point for zero volts, to my mind. You can't get negative zero, or positive zero. It's zero.
A better term to use would be plus nine volts, or minus nine volts. Totally accurate.
Aren't there effects that have a positive ground and effects with a negative ground, like say the pepper spray, or am I way off?
Quote from: jimilee on October 26, 2013, 03:52:46 AM
[...]
Aren't there effects that have a positive ground and effects with a negative ground, like say the pepper spray, or am I way off?
There are effects where the ground is positive relative to the power rail and vice versa.
I'd also guess that term comes from the battery connections. But, there's also the point that, since these are potentials, there is no absolute reference point nor is there even a preferred direction for what's positive and negative. The only thing that's really important is the relative difference between two points. Calling ground 0V is only a convention and the direction for greater potential being positive is only a convention too.
Yes. Ground is ground. It's more accurate to refer to the differently powered circuits as +9V or -9V (plus 9 volts or positive 9 volts vs minus 9 volts or negative 9 volts).
It bugs me too.
Jacob
Quote from: alanp on October 25, 2013, 11:25:35 PM
Ground is a reference point for zero volts, to my mind. You can't get negative zero, or positive zero. It's zero.
Quote from: jkokura on October 26, 2013, 04:56:06 AM
Yes. Ground is ground.
Ground is ground and still it could be anything, any potential.
Ground in a schematic could be anything, any potential. There will be other places with different potential, higher or lower than ground. To make this happen you need to hook up (a) DC source(s) accordingly. Convention has it to call the higher potential of this souce positive and the lower potential negative, meaning a 9V battery will give you +9V at the positive pole measured against the negative pole. And it will give you -9V at the negative pole measured against the positive pole. Now you
could call ground positive or negative according to how you hooked up your DC supply. (But you better shouldn't even if this terminology sadly is established.)
The confusion starts as soon as you hook up a circuit to things that somewhere touch earth, which gives you a reference point usually called 0V. Now, any potential in a schematic could be referenced to this, but most of the time this will be what is called ground in your circuit and most of the time this will also be the negative (lower potential) side of the DC supply. In this "grounded ground" situation it gets confusing speaking of positive or negative ground as nobody would call 0V negative. (It is a convention to see 0 as positive, but most wont apply this to 0V.)
Quote from: alanp on October 25, 2013, 11:25:35 PM
One thing that continuously bugs me is how people refer to "negative ground" or "positive ground". Ground is a reference point for zero volts, to my mind. You can't get negative zero, or positive zero. It's zero.
I think the main reason for this positive/negative ground can be found in the DC jack.
Usually you have this schematic where there is a - or a + sign for the inner pin.
If you look at it from a non-technical view you could refer to it as positive or negative ground.
Makes sense ?
interestingly, it's not just electronics that suffered from this positive/negative ground confusion; many cars had positive ground schemes for the starters up until, say, 1960 or so. i'm sure it made for some "interesting" situations when people needed to jump start a positive ground car from a negative ground car.
Quote from: Mike B. on October 26, 2013, 01:00:26 AM
Also, it's a legacy term. Effect pedals are traditionally battery powered, and the only way to get -9v out of a 9v battery is to connect the positive terminal to ground.
This is spot on.
I agree though. -9V, +9V operation is a much better (and more accurate) description.