Aim TTi EL302RT PSU : understanding the specs, and comparing
Have you thought of asking TTi Directly?

Email: info@aimtti.com

They usually respond very quickly and will pass the question onto the design engineer if nobody in sales is sure of an answer.  I used to work for them and have designed some of the power supplies on that data sheet though not this particular model.

But to answer your questions directly.


  Are all the 3 channels isolated, have their own ground? Even that middle one which goes up to 5V?


Yes each output is independent and floating.  The front panel shows the level of isolation from earth (to either 0V or output) which is 300V.  It is not obvious from the specification but this also applies between any two outputs. This may not be relevant in this case as its max output is 30V.


  The measured or displayed voltages, spec says resolution is 10mV, but the output regulation performance I'm not sure I understand it is spec'ed : it says, Line regulation "&lt; 0.01% for of maximum output for 10% line change". So does this mean, for a 30V line (max V output), if I do a 10% change on the dial knob(s) , the output V will change by 30000 mV * 0.001 = 30 mV ..? It doesn't , it seems, say anything about the smallest change I can make - can I make only a 1% change with Fine knob ? If 30mV is 10%, I hope then if I can change by 1% that's a 3mV change..?


Regulation and metering are separate things.

Metering:
Resolution 10mV simply because that's the value of the lowest digit.
Accuracy: 0.3% &pm; 3 digits

To understand what this means let's say the output is actually 30.00V

30V - 0.3% = 29.91V minus 4 digits is 29.87
30V + 0.3% = 30.09V plus  4 digits is 30.13

The display can show anything between 29.87 and 30.13 and still be in specification.

Lets say the output is actually 0V, &pm;0.3% is still zero volt so in theory the display can be between -0.04 and 0.04 and still be in specification. This model does not display negative values however so will never show &lt;0.00.  The bottom end is calibrated in the factory using a small positive voltage so it displays a very small number to allow for this.

Line regulation and load regulation are a measure of how much the output is allowed to change as the mains and load change but the display is based on what is actually being output.

Setting resolution is purely analogue so you can change the output by less than a mV if your hands are steady enough.


  And also I wanted to ask for your experienced opinion, do you think EL302RT is much better than Rigol DP-832 or other way? ...


No comment, I have never used this Rigol supply.  I can personally vouch for the TTi model but Rigol also make nice products.  On this site we are also not supposed to make shopping recommendations.