Author Topic: Power supply for home lab - do I really need a R&S?  (Read 11373 times)

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Offline pdenisowski

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Re: Power supply for home lab - do I really need a R&S?
« Reply #100 on: October 14, 2024, 08:21:24 am »
This is a bit disappointing. Im still set on buying an NGA102 as the problem wont bother me much in my applications. But after i saw Daves video where he showed this issue and studying the firmware notes i was convinced that they have tackled the issue. They are well aware of it. See the firmware notes:

https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/pdm/firmware/5601_9009_00/NGA100_ReleaseNotes~1.pdf

Does anyone here have a NGA100 with up to date firmware who can comment?

Here's the output of the NGA142 connected to a 50 ohm load



 
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Offline KungFuJosh

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Re: Power supply for home lab - do I really need a R&S?
« Reply #101 on: October 14, 2024, 04:19:07 pm »
Here's the output of the NGA142 connected to a 50 ohm load

Can you do some more tests that put that in the context of the other tests that have been done? For example: https://www.eevblog.com/forum/testgear/lab-power-supply-turn-on-and-off-characteristics/msg5667833/#msg5667833

I would like to see current response also, not just voltage.

Thanks,
Josh
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Offline mhsprang

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Re: Power supply for home lab - do I really need a R&S?
« Reply #102 on: October 14, 2024, 04:22:06 pm »
Here's the output of the NGA142 connected to a 50 ohm load

Can you do some more tests that put that in the context of the other tests that have been done? For example: https://www.eevblog.com/forum/testgear/lab-power-supply-turn-on-and-off-characteristics/msg5667833/#msg5667833

I would like to see current response also, not just voltage.

Thanks,
Josh
That is the current response. The oscilloscope shows that the voltage doesn't rise above 40 mA * 50 Ohm. And since this is a resistor, the current flow is idential in "shape" as the voltage across the resistor.
 
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Offline KungFuJosh

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Re: Power supply for home lab - do I really need a R&S?
« Reply #103 on: October 14, 2024, 04:31:49 pm »
That is the current response. The oscilloscope shows that the voltage doesn't rise above 40 mA * 50 Ohm. And since this is a resistor, the current flow is idential in "shape" as the voltage across the resistor.

Good point. I guess I was thrown off by how pretty it looks. I guess the OP really does need an R&S. 😉

But also, I'm curious about lower current settings too. For example, setting a 10mA or 20mA current level. Some PSUs behave differently depending on the current setting.

For example, my SPD3303X only overshoots when set below 30mA, as 29mA is the typical overshoot on power activation.
« Last Edit: October 14, 2024, 04:54:40 pm by KungFuJosh »
"Right now I’m having amnesia and déjà vu at the same time. I think I’ve forgotten this before." - Steven Wright
 

Offline mhsprang

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Re: Power supply for home lab - do I really need a R&S?
« Reply #104 on: October 14, 2024, 05:09:12 pm »
@KungFuJosh,

I agree about the lower current setting. I sort of started this by observing a huge overshoot on my R&S NGE103, which is now being investigated by R&S. That overshoot is happening at all currents below 140 mA and is always up to 140 mA.

So, maybe this NGA 142 is doing allright at 40 mA but behaving bad at 10 mA. Maybe @pdenisowski could repeat this test at 10 mA as well.
 
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Offline KungFuJosh

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Re: Power supply for home lab - do I really need a R&S?
« Reply #105 on: October 14, 2024, 05:23:14 pm »
@KungFuJosh,

I agree about the lower current setting. I sort of started this by observing a huge overshoot on my R&S NGE103, which is now being investigated by R&S. That overshoot is happening at all currents below 140 mA and is always up to 140 mA.

So, maybe this NGA 142 is doing allright at 40 mA but behaving bad at 10 mA. Maybe @pdenisowski could repeat this test at 10 mA as well.

Uh oh, don't let R&S know my little Siglent PSU is behaving better than their PSU that costs 3 times as much. Or maybe that will get them to fix it faster. 😉😉
"Right now I’m having amnesia and déjà vu at the same time. I think I’ve forgotten this before." - Steven Wright
 

Offline mhsprang

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Re: Power supply for home lab - do I really need a R&S?
« Reply #106 on: October 14, 2024, 06:45:57 pm »
Uh oh, don't let R&S know my little Siglent PSU is behaving better than their PSU that costs 3 times as much. Or maybe that will get them to fix it faster. 😉😉
They already know that  ;D
 
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Offline pdenisowski

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Re: Power supply for home lab - do I really need a R&S?
« Reply #107 on: October 14, 2024, 07:37:47 pm »
So, maybe this NGA 142 is doing allright at 40 mA but behaving bad at 10 mA. Maybe @pdenisowski could repeat this test at 10 mA as well.

I'll have to borrow another NGA to test against, but the NGA is a purely linear power supply, so I expect something very similar.
Test and Measurement Fundamentals video series on the Rohde & Schwarz YouTube channel:  https://www.youtube.com/playlist?list=PLKxVoO5jUTlvsVtDcqrVn0ybqBVlLj2z8
 
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Offline salomonander

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Re: Power supply for home lab - do I really need a R&S?
« Reply #108 on: October 16, 2024, 12:34:34 pm »
Do these spikes in current mode only happen with number small number below 20-30mA? Or does it also happen when i limit it to say 60mA? Thanks
 

Offline KungFuJosh

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Re: Power supply for home lab - do I really need a R&S?
« Reply #109 on: October 16, 2024, 05:00:54 pm »
Do these spikes in current mode only happen with number small number below 20-30mA? Or does it also happen when i limit it to say 60mA? Thanks

That depends entirely on the brand/model of PSU. My Siglent SPD3303X only spikes up to ~29mA, so anything below that will see more current for a very short spike before dropping and then going up to the current setting. For anything over 30mA it doesn't matter since the spike hasn't ever gone above that in my tests.

Different brands have shown different results. Some much better, some much worse.
"Right now I’m having amnesia and déjà vu at the same time. I think I’ve forgotten this before." - Steven Wright
 
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