Power supply for home lab - do I really need a R&S?

[mhsprang]

Thanks to everyone for all the analysis and comparison.  As I mentioned above, I've already communicated all of this to the power supply team in Munich and we are investigating.  It would also be very helpful if the OP could contact our technical support about this and/or contact their R&S sales representative as well.

One (potentially ignorant) question:  has the behavior of the NGE (or other manufacturers' supplies) been outside of its published specifications? 

I've seen lots of test results for lots of supplies (and again, many thanks for those), but I haven't seen any comparisons of experimental results to published specifications.  That would have been one of the first things I checked - is a given supply "in spec"? 

My apologies if that's a dumb question.

Yes, I sent an email to R&S support yesterday about this.

And yes, I feel this is outside the specifications for exactly the reasons ArdWar just stated in his reply #73, just above.

[blackdog]

Hi, :-)

KungFuJosh asked for some explanation of what scope probe I was using, which can be seen below in the picture.
Cost about 1850$ *grin*
The comment above is a hint to the major measuring instrument manufacturers who regularly charge outrageous prices for all kinds of probes.

Probing setup
The tests I did with current limiting around 10mA required a 50 Ohm resistor and about 1-Watt.
I used 2x a 100 Ohm resistor in parallel with a 1M Banana Crock cable from GW Instek and to the scope I used one 1M BNC to Crock cable.
One and all can be seen in the photo below.

I have been thinking about running the measurement setup “HF”.
But on reflection this was not really necessary, this because the LAB power supplies tested have between 100uF and 680uF across the terminals.
This does not allow fast rise times in the measurements.

I use two already older scope probes on my test benches from Micsig for commonmode measurements and current measurements, which are the DP10007 and the CD2100B.
For my work these probes are satisfactory and they are very affordable.
But Micsig also has faster probes available and still affordable prices.
In my measurements, however, these Micsig probes have not been necessary, K.I.S. was a good mindset here, so i used basic cables.

First the pictures


The used probe

.

Scoop setup
In this photo, I left the settings for channel-1 on, so it is easy to see what I worked with.

Coupling
The coupling is DC

Bandwidth
Bandwidth is 20MHz, otherwise too much noise is visible.
These measurements are about waveform and level and not because I want to see everything that happens while measuring.
I do always start with the “window wide open” when making measurements.
Then I have an impression if there are things that also come into play that I need to take into account.

Pressentation
Most measurements I show on forums are “without” noise, so that the attention goes as much as possible to the measured signal of interest.

Scale factor
So the next setting is the scale of the channel used, and this is set by using the “User1” setting of the Siglent scope.
Here the setting is 50V per ampere.

Input impedance
This should be set to 1M Ohm so as not to blow up your scope. 

Unit
This should be set to Ampere unit, this because we are measuring the peak current behavior of a LAB power supply.


.

And now for some comments on LAB Power Supply's.
I've tested a lot of different circuits and I've developed a fondness for the “Harrison Consept.”
That is that the reference section has its own floating power supply and the control current for the power section usually comes from a current source.

Then there are two control loops one for current and the other for voltage.
Which then control the current through two diodes to the Power section.

Nowadays it is a whole lot easier to make a fast responding LAB Power Supply.
The advantage is that it is then possible to keep the capacitor across the output terminals low and still have a fast responding loops with good dynamic behavior.

This has not yet caught on with many manufacturers,
a thick capacitor across the output terminals and slow opamp/power transistors is much cheaper.

Better loop contro en component choices
Furthermore, a current source that always draws current from the output(when the channel is turned on) helps well for excellent dynamic behavior.
There are also opamps available these days that have a large phase and gain margin, look at the ADA4625 models from Analog Devices.

This opamp series has low noise, little bias current, fast and little offset, but above all a phase margin of 88 Degrees at 100pF capacitive load, which is excellent!

Everything I have written here is mine no AI, but translated by deepl.com
And I'm a dyslexic Monkey, which can lead to pretty crooked sentences. 

Kind regards,
Bram