DP832 Rigol power supply question. (Sharing a common)

[Plasmateur]

My question is in regard to channel 2 and channel 3 of the power supply found here: https://www.tequipment.net/RigolDP832A.html

In the bottom right corner you can see the negative terminals of ch.2 and ch.3 of the power supply share a common - and in another thread on here someone had said they share the same ground.

But I didn't think these channels were referenced to ground until those terminals were physically connected to ground.

So if ch.2 was set to 10V, that should be the potential difference between the terminals of ch.2 - and if the positive terminal of ch.2 was measured with a an oscilloscope probe tip, there would be some oscillating voltage measured until the negative terminal was connected to earth ground - at which point the scope should read 10V flat.

Is this correct?

 
 

[ledtester]

In the bottom right corner you can see the negative terminals of ch.2 and ch.3 of the power supply share a common -  and in another thread on here someone had said they share the same ground.

I think they were saying the same thing. Often "ground" is used to refer to the negative terminal of a power supply, and it doesn't necessarily mean it is connected to earth ground. Channel 2 and 3 share the same negative terminal.

The point is that ch 2 and ch 3 are floating but not isolated from each other. Ch 1 is isolated from the others, so you can put, for instance, ch 1 and 2 in series by connecting ch 1's + terminal to ch 2's - terminal. However, if you connect ch 2's + to ch 3's - you'll short circuit the supply.

Since they are floating, ch 2 and 3 are not reference to ground by the supply. But once you ground, say, ch 2 you are also grounding ch 3.

[Plasmateur]

In the bottom right corner you can see the negative terminals of ch.2 and ch.3 of the power supply share a common -  and in another thread on here someone had said they share the same ground.

I think they were saying the same thing. Often "ground" is used to refer to the negative terminal of a power supply, and it doesn't necessarily mean it is connected to earth ground. Channel 2 and 3 share the same negative terminal.

The point is that ch 2 and ch 3 are floating but not isolated from each other. Ch 1 is isolated from the others, so you can put, for instance, ch 1 and 2 in series by connecting ch 1's + terminal to ch 2's - terminal. However, if you connect ch 2's + to ch 3's - you'll short circuit the supply.

Since they are floating, ch 2 and 3 are not reference to ground by the supply. But once you ground, say, ch 2 you are also grounding ch 3.

Okay, that's exactly how I thought it worked.  Thanks for taking the time to reply.

[rstofer]

Which means that when you need +15V, -15V and +5V, Ch2 MUST be the +15V output.  There a wiring diagram for this in the User Manual.

This might be used for some dual rail op amps feeding into a single rail low voltage op amp before feeding into a uC ADC input.