No Voltage Reading to Ground

Also known as an ESO fault.

_{^{Equipment Superior to Operator.}}

verify you have a ground

For sure, floating power supply. So often people confuse common with ground. To avoid ripple and ground noise you typically don't connect a regulated supply common to ground.

This reminds we of waaaay back when I was a humble test engineer (ok I've never been all that humble).

We had a graduate who couldn't wire two bench power supplies together to give a plus and minus 15v supply.

When I told him to connect the + of one to the - of the other and then wire those to the ground post he thought I was winding him up.

Once you have the concept of a completely floating supply which can have either terminal referenced to ground (or some other supply) it's easy.
Del

A guy I once worked with had a sign on his desk that read "It's hard to be humble when you're as great as I am."

LOL!

Our variable HP power supplies are marked + and - on the terminals, but there is no center tap.

The HP bipolar supply we have also has a + and a -, but the center tap is marked COM.

I don't think there is a universal convention as to how power supplies are marked, so it could be any number of ways.

All it is normal because the output is insulated from GND by the output trnsformer and is called "separation" if also have a grounded screening between primary and secondary coils(else wil exist an capacitiv coupling from mains to output...)

Don't get confused with the use of the terms "ground" and "earth", particularly in the electronics field. They are not necessarily the same.

"Earth" generally, but not always, refers to the general mass of earth, or a connection thereto.

If an appliance is said to be "earthed" you can be pretty sure that it is electrically connected to the general mass of earth, and therefore should be at earth potential or zero volts.

On the other hand, "Ground" whilst regularly and confusingly used in the above manner, is more often used to denote the common point of a multi output supply as the OP seems to have, or simply one side of a single voltage power supply, and it may or may not be connected to, and thus at the same potential, as the general mass of "earth".

Many power supplies have a "ground" (usually the -ve rail) that is kept above "earth" potential for noise limitation and/or isolation purposes.

Most motor vehicles use the chassis as "ground" but it's not at "earth" potential.

In large computer systems you usually have two grounds, logic and safety. The names tell you everything......they are usually linked AT ONLY ONE SINGLE PLACE in each machine.

You can remove this link if needed by some special faultfinding techniques. Sometimes problems are fixed by removing it, sadly!!!! Though usually the house electrician can improve matters dramatically if talked to nicely.....

YES! This is why I dislike the use of the word "ground" and prefer the term "return"

and i or number "0" zero is good also.the Ground is good when you see the 0 ,+,- in an electronic circuit

Good point, many forget/do not understand this!!!

I forget sometimes....

......which is exactly as it should be in all respects including safety. The OP is worrying about nothing......

In fact he may even be worrying about something negative
Del

LOL!

The output is floating, which is normal.

The two terminals should be labeled + and -. Not +24 and -24.

Think of it like a car battery sitting on a table: measure from earth to the neg terminal, zero; measure from earth to the pos terminal, zero; measure from the neg to the pos terminal, 12V. (Or you could do the same "experiment" with an AA cell.)

Well said, its not Rocket science is it?

Just to clear my confusion. Since Voltage difference is potential between two points and the voltage at ground is considered zero. By measuring battery voltage(or any voltage)with respect to ground .Arent you completing the circuit with your multimeter. Shouldnt the multmeter give the voltage on the battery instead of 0

Well put.

No: the battery is floating.

Although the multimeter has a very high impedance: it's still very low compared to the air, so when you try to measure from earth to the positive terminal of the battery you are effectively shorting the positive terminal to earth (only half of a "circuit" has been made).

Try this thought experiment: put some AA cells on an insulated table. You expect (or at least you used to) the negative terminal of each to be at 0V (relative to earth) and the positive terminal to be at 1.5V. But what happens when you start joining them together? Does one of the -ve terminals take precedence over the others?

No.

You are misleading yourself. If there is no "path", there will be no electron flow e.g.no voltage, no current.

You must have a complete path for current to flow and voltage to be measured.

The usual reason for not grounding any part of a low voltage DC circuit is to keep electrical noise/pickup away from possibly sensitive electronics.

Maybe it was just a fluke. Sorry!

most dc industrial power supplys are non- grounded on the dc side

you have to strap the negitive to ground

....if you wish the supply to be ground referenced that is!!!! You forgot that bit.

Most power supplies are not referenced to anything except themselves, provided a transformer is in there somewhere.....

I agree completely with answer of number #5.

Your power supply is floating (not connected to ground). There are various reasons to do this. One is to prevent ground loops which can cause measurement errors.

So what is the problem? That's what is supposed to happen!

I assume that you mean there are two output terminals one marked + and one marked -. Also you have to define what you are calling "Ground". Is it the case or the ground pin on the AC plug if the plug has a ground pin.

With the power supply disconnected from the AC source measure the resistance of each terminal to the metal case of the supply and the ground pin on the AC cord. That also assumes that there is a ground pin on the AC cord.

Depending on the resistance reading you get you can determine if the either of the terminals are connected to the ground pin of the AC plug.

Marv

If you have a center tap, make sure you have a good connection from the center tap to ground.

There may be particular reasons for requiring the center tap to be grounded due to the particular design of the attached circuitry, but there is otherwise no reason for the center tap to be grounded.

Generally speaking, most "bought-in" power supplies will not have it grounded, but maybe the circuitry they attach to has a grounding to Logic ground or similar.

With your inaccurate comment you may be misleading other members here.......