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I was looking at a print today and noticed that the feed 24v and the "return" was 0V. Anyone know why they list it that way?
 

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Generally the negative side of the power supply is grounded so its saying your feed is 24V to ground and your return is 0V to ground.
I know I was getting caught up in the semantics, I've just never seen 0V on a print before. Wanted to see if there was anything more to it.
 

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simply comes down to "who drew the prints"?

You may see +24 and 0 (as you are now), +24 and -24, 24 and 0, or even nothing but wire numbers without a voltage call-out. Like 74325KLS and maybe 74101KLD.

I personally prefer +24 and 0, but thats how I draw them.
 

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I was looking at a print today and noticed that the feed 24v and the "return" was 0V. Anyone know why they list it that way?
Quite common here in oz.... common to see positive wire from power supply marked +24vdc and the common marked 0vdc...

Frank
 

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simply comes down to "who drew the prints"?

You may see +24 and 0 (as you are now), +24 and -24, 24 and 0, or even nothing but wire numbers without a voltage call-out. Like 74325KLS and maybe 74101KLD.

I personally prefer +24 and 0, but thats how I draw them.
having a -24 would lead me to believe it is an AC circuit, since DC is either a positive number or zero.
 

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having a -24 would lead me to believe it is an AC circuit, since DC is either a positive number or zero.
Dc can and does have negative voltages all the time. For example +/-10V is a very common arrangement for analog DC signals.

On a related note "0v" certainly does not necessarily mean 0v to ground. It simply means it is the zero volt reference point for that DC system, not necessarily with respect to ground. Sometimes that point is bonded but even if it is floating relative to ground, 0v is still valid.
 

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I wanted to clear up some misleading information in this thread. Remember that voltage is a relative difference in charge. 0V in fact may mean just that the point is considered the origin or relative common for the circuit. In some cases it can be deadly to assume that 0V is grounded, especially in circuits using high voltage isolation.

An interesting use of 0V I have come across is in a negative logic system. The system took a standard 24V power supply and tied the + lead to ground. That wire was labeled 0V. The other wire was labeled -24V.

I have also seen P24 N24 used for +24V and a grounded common. I believe that notation is more Asian than North American or European.
 

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I wanted to clear up some misleading information in this thread. Remember that voltage is a relative difference in charge. 0V in fact may mean just that the point is considered the origin or relative common for the circuit. In some cases it can be deadly to assume that 0V is grounded, especially in circuits using high voltage isolation.

An interesting use of 0V I have come across is in a negative logic system. The system took a standard 24V power supply and tied the + lead to ground. That wire was labeled 0V. The other wire was labeled -24V.

I have also seen P24 N24 used for +24V and a grounded common. I believe that notation is more Asian than North American or European.
Yep, that's why many PLCs and other industrial electronics with 24VDC inputs will have the ability to be used as "Sink or Source" by simply changing which side of the 24V you connect to it. It's mainly the Japanese that do that, but because they dominated the Asian marketplace for so long, it's still a convention used over there quite a bit.
 

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Yep, that's why many PLCs and other industrial electronics with 24VDC inputs will have the ability to be used as "Sink or Source" by simply changing which side of the 24V you connect to it. It's mainly the Japanese that do that, but because they dominated the Asian marketplace for so long, it's still a convention used over there quite a bit.
Its most of the other side of the globe, a lot of places use NPN rather than PNP.
 

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You already have some great responses here, but I'll weigh in just for the heck of it: I've also seen +24VDC and 0VDC, as well as +24VDC and -24VDC. In college I grew accustomed to using +24VDC and -24VDC, but at my place of employment we always use +24VDC and 0VDC.

In most cases the notation typically depends on the established practice by your immediate company or organization. The logic behind the notation, however, is based on your chosen reference node. If your reference is +24VDC, then you'll measure a negative voltage because the conventional flow of current is positive to negative. On the other hand if your reference is real ground (in the case of a floating ground, a real ground may be assumed for the sake of consistency in nomenclature), then you'll measure 0VDC. To summarize, the notation is intended to illustrate the potential difference between two points, a reference node and a source node. The reference and source nodes are often assumed based on known or inferred polarities, but it is very dangerous to make this assumption.

As Jabberwoky pointed out for everyone :)thumbsup:), 0VDC can be misleading, which is why I still personally prefer the + and - nomenclature. +24VDC and -24VDC tells me more about the system, which is more useful information, especially in complicated power distribution.

I don't believe either nomenclature is wrong, but it would be interesting to know if IEEE, UL, IEC, or NEC guidelines address this question. If any of them do, I suspect it would be a recommended best practice.
 

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P + m

:rolleyes:My German machines use P + M for plus and minus
 
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