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Bench power supply Ground levels

Bench power supply Ground levels

Bench power supply Ground levels

I'm guessing I already know the answer to this but I better ask anyway to be sure.

If I buy a dual channel bench power supply, will the two channels be totally independent or will they share the same Ground level?

Taking it one step further, will the DC Grounds have any connection with the mains earth or is everything isolated?

I realise the chassis will be grounded to the mains earth point, but am curios if two DC channels are totally isolated and independent.


RE: Bench power supply Ground levels

No can say. It can be either way.

All they need to do is use isolated windings on the transformer side and they could be entirely independent, but often they don't bother using instead a center-tapped transformer and then the two channels will share a common.

Sometimes if the supply has a 5V and then +/-15V outputs the 5 will be isolated on its own winding and the +/-15V will share.

You have to see the supply's actual specs.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Bench power supply Ground levels

Completely independent channels will probably be harder to find and cost more. As a reality check, I would compare the price of a power supply with independent channels with the price of two single channel supplies.

"Why not the best?"
Jimmy Carter

RE: Bench power supply Ground levels

Thanks for your replys.

I just read the spec' on a Siglent which states:

3 independent high precision output?30V/3A*2,2.5V/3.3V/5V/3A*1,total 195W power

4 digits voltage and 3 digits current display, min resolution: 10mV, 10mA

Three output modes: independent, series and parallel

Does that seem to describe what I am looking for, or does that independent term mean something different?


RE: Bench power supply Ground levels

Give us a model number.
Independent and isolated are not always the same.
However the possibility of series connection may imply isolated.

"Why not the best?"
Jimmy Carter

RE: Bench power supply Ground levels

The number and colour of the output terminals (5-way binding posts) is often a clue, but you'd still have to double check.

With a current limited power supply, one can safely run an experiment to quickly check. Start with zero current and slowly adjust it up to see if anything is flowing in an unexpected direction.

RE: Bench power supply Ground levels

@waross It's a Siglent SPD3303C

@VE1BLL I can't really test anything yet since I haven't bought it. I'm trying to make sure before I buy it, so as I don't buy the wrong thing.

I suppose the best answer would be a confirmation from someone who already has one.
It's quite easy for me to misinterpret the specifications.

RE: Bench power supply Ground levels

Most dual power supplies have Qty 5 of the binding posts on the front.

Typically: Red & Black, Green, Black & Red.

The two internal power supplies typically have to be completely isolated from ground because the user is entitled to connect either Red (+) or Black (-), for each supply side, to the Ground. The supplies are designed and intended to be used as (for example) +5VDC and +12VDC, *or* +/- 15VDC. It's a design intent that both sides are isolated from ground until the user plugs in the banana plug cables.

The small risk is that a given example might not be typical.

So: Pick one, and post the model number. Somebody here will know.

edit: Ah, you did. 'Siglent SPD3303C'. I think yes they're isolated, but wait for others to confirm.

RE: Bench power supply Ground levels

Mrs. Spock already posted her answer:

"Three output modes: independent, series and parallel"

Which, from the power supply's datasheet states:

Series and parallel functions allows two channels to be easily combined into one output with more power output ability, doubling the supplied voltage or current. http://www.siglentamerica.com/USA_website_2014/Doc...

I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers

RE: Bench power supply Ground levels

That's great.

I'm just a bit dyslexic when it comes to datasheets, so it's good to get some reassurance before coughing up the money.

I'm happy to buy it now.

Thanks everyone.

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