Well, Im just trying to figure out how every little piece of a power supply works exactly. Right now, I am curious about the term "bi-polar power supply". What little understanding I have of these is they they have both a positive polarity and a negative polarity, in addition to a ground, as compared to what I suppose would be called a "uni-polar power supply", which would presumably have only a ground and either a pos or neg.

So, both linear bench power supplies I use have both pos and neg outputs, in addition to ground, so would I be correct in assuming that those are both bi-polar?

As far as design, would, for example, my 0-36V variable power supply actually in some sense be a -18V and +18V power supply? I also have to ask at what design stage this comes about, I am thinking it begins with the transformer, but basically Id like to understand the entire design.

If my assumptions are correct, this means that on, for example, my Power Designs 3650 (0-36V), I could use the pos and ground to achieve a max output of 18V, or neg and ground for -18V. I am not entirely sure of the motivation to do such a thing but by all means Id love to learn some appropriate uses.

Thanks for teaching me

-Chris P

A 0-36 variable suppy mans you get a max. supply of +36V.
Your bench power supply probably has three knobs. Red, Black and Green(?)
Red for positive voltage, green for negative and black for ground. In this case the voltage varies from the negative maximum voltage to 0 to positive maximum voltage.

My one I have here at home is a Power Designs 3650. The pos is red, and both the neg and gnd are black. Its voltage is adjustable between 0 and +36V. My one at work may have green for negative, I cant remember at the moment, but that one too adjusts between 0 and about +31V.

On both, their advertised voltage range is achieved by using pos and neg, and leaving ground unused. Actually none of us at work really know what the ground terminal is used for... So far every use I have had for a power supply is the equivalent of using it in place of a battery.

Oh is it? Well, its always safer to use the ground. There is a meter(indicator for voltage) right? Does the scale vary from 0 to the max. value or does it include negative scale?

Well I just physically tested a DC fan using the pos and gnd, no power. So...

Originally Posted by Cobalt60

Well I just physically tested a DC fan using the pos and gnd, no power. So...

U mean the fan didn't run? Funny! Well here(in India) we've always used Red and Black. Infact the lab attender threatened us and asked us not to touch the green knob

The one I have here has an analog gauge, 0 through 36V, as well as 0 through 5A. My one at work has a digital display, I dont think Ive ever seen it show a negative reading, and at work we all use the neg and not ground. So far I have not noticed much of a functionality difference between the two power supplies.

Check out the meter range. It'll give you an idea if your supply is 0-36V or -18V to +18V

Originally Posted by Cobalt60

The one I have here has an analog gauge, 0 through 36V, as well as 0 through 5A. My one at work has a digital display, I dont think Ive ever seen it show a negative reading, and at work we all use the neg and not ground. So far I have not noticed much of a functionality difference between the two power supplies.

Hmph.. well you sure the two knobs are black? My friends and I were getting confused with the colours in school... sometimes they use a very dark bottle green-blackish colour for the green knob

As far as I know.. when the black and the green knobs are used then your supply provides you with negative voltage...

My bench supply has ground, negative, and positive terminals, but is only advertised as a 0 through +36V supply, is this a bi-polar supply?

And yes, the fan did not run. To get power on this supply I must use the pos and neg terminals. However, the power supply is old and I am not 100% sure that it is fully functional.

Originally Posted by Cobalt60

However, the power supply is old and I am not 100% sure that it is fully functional.

Now you didn't mention that one!

So are my bench supplies bi-polar or uni-polar? Somewhere internal to the design is there indeed a -18V and +18V?

And indeed the fan did not work when connected to pos and gnd. I suppose if the grounds are isolated that would make sense. And my supply here is definitely a red and 2 black, at work I just cant remember.

So how exactly would I use a "reference ground"?

I really can't work out the range!!! (I've very poor practical knowledge, sorry). I really hope someone helps you Try this... (I hope its safe) Turn your voltage varying knob to its maximum, use a DMM and check its voltage... repeat this with red-black, green-black combinations.