Advice on a low noise precision programmable power supply? - Page 1
Forum section: electronics / testgear

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: July 05, 2024, 08:35:35 pm
content: I am currently running two pretty cheap switching power supplies and have added some common mode filtering to them, I have been able to significantly reduce the amount of output noise and there great for things like battery charging, testing high voltage Zener diodes, digital work etc... but I am experimenting with low noise analog pre amp type of circuits and my currents PSUs cause the power rails to swamp the the incoming signal.What I am looking for is a dual channels, configured in bi-polar, that can be adjusted by at least 10mV/1mA, at least 24V and 2A, low low noise like 5mVPP but lower is better, and lastly it MUST have binding posts that have standard spacing and fit banana to BNC! A tracking dual channel supply would be nice along with 1mV/1mA adjustment, but even two single channel supplies are not a deal breaker.I've been looking at all kinds of options from new to used, I'm not that picky either way. Originally I was going to buy a Siglent SPD3303X since all my other gear is Siglent, but the banana plug spacing kills this option! I have also looked at theKorad suppliesandthis one from circuit specialists. The problem is there is no one out there showing the ripple and common mode noise that come out of these power supplies, not even the Siglent. I dont mind buying some used Keithley or Keysight supplies, but are they any less noisy or even that much better than a newer Siglent/Rigol etc?

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 05, 2024, 08:56:13 pm
content: Why is the banana plug spacing so important? That seems like it would be the easiest thing to work around. I dunno if they changed the spacing for the SPD4000X, it might be worth a look.

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: July 05, 2024, 09:12:10 pm
content: I didn't realize there was a 4000x. I use BNC a lot and i don't want to make a janky adapter, its kind of a point... make your shit compatible with the same adapters we have been using for over 50 years..

author: tautech
author_rank: Super Contributor
timestamp: July 05, 2024, 09:46:13 pm
content: Quote from: rwgast_lowlevellogicdesin on July 05, 2024, 09:12:10 pmIt's very new.4 channels and if following the single channel SPD1000X models terminal layout will be 3/4"/19mm spacing.https://int.siglent.com/products-overview/spd4000x/

author: nctnico
author_rank: Super Contributor
timestamp: July 05, 2024, 09:51:50 pm
content: Look at Gw Instek Gpp 4000 series. These also have a dc load function and 4 fully controllable channels.

author: Someone
author_rank: Super Contributor
timestamp: July 05, 2024, 10:24:08 pm
content: Quote from: rwgast_lowlevellogicdesin on July 05, 2024, 08:35:35 pmPossibly not better (at some given condition, with the unit on hand), but if they provide guaranteed noise specifications then you won't get any worse than that.

author: tautech
author_rank: Super Contributor
timestamp: July 05, 2024, 10:30:43 pm
content: Quote from: Someone on July 05, 2024, 10:24:08 pmExactly.Siglent PSU's do clearly provide a ripple and noise spec in datasheets, generally ~350uV and just try to measure this with a scope.Not as easy as one might think.......

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 05, 2024, 10:35:12 pm
content: Quote from: rwgast_lowlevellogicdesin on July 05, 2024, 09:12:10 pmI hear that. If I had to choose between specs, and the spacing of the banana plugs, I'd choose the specs. No adapter needed. If you're using banana plugs on both sides, use the standard on one side, and two loose banana plugs on the PSU side. Then nobody's spacing will bother you. 😉

author: Electro Fan
author_rank: Super Contributor
timestamp: July 05, 2024, 10:35:20 pm
content: Quote from: rwgast_lowlevellogicdesin on July 05, 2024, 08:35:35 pmDepends on your priorities (budget, specs, etc.) but regarding Korad, here are some links that show some ripple tests.There are some links within the third link post below that will provide some useful parts info. One of the keys to measuring ripple with a scope probe is to get a proper BNC to probe adapter - see attachment. (Note the Korad uses standard binding post spacing.)Another thing to consider is how well a unit can be adjusted. Korad provides a test and adjustment procedure. I did it years ago and knock on wood everything continues to run well. I'm pretty confident that the Korad is reasonably close to within about .01V and .001A. Along the way I purchased a 2nd KA-3005; the first was a P, the second a D. Not much difference in price but if you don't need the P you can go with the D.https://www.eevblog.com/forum/testgear/korad-kd3005d-bench-supply-power-on-spike/msg3515618/#msg3515618https://www.eevblog.com/forum/testgear/korad-kd3005d-bench-supply-power-on-spike/msg3521224/#msg3521224https://www.eevblog.com/forum/testgear/korad-kd3005d-bench-supply-power-on-spike/msg3529898/#msg3529898Edit: Added Korad adjustment procedurehttps://www.eevblog.com/forum/testgear/korad-3005p-calibration/msg4172746/#msg4172746

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: July 05, 2024, 11:25:22 pm
content: Is 350uV a pk to pk, or an rms measurement. Most everything I see says under 1mv rms... which doesn't always mean a lot based on how fast the peaks are.Its already been stated the new Siglents are 3/8th's spacing which is fine, i feel like connector standards are important.. it isn't like Siglent are the only game in town and I cant get the same performance from Rigol or Instek or dozens of brands, most brands use standard spacing so in the end it should be easier to find a PSU with 3/8 posts than some other weirdness. We all find different things important.The Insteks actually look pretty nice and there about the same price as the 4000x, ive been looking at some used Kiethly too. 500+ is a lot for a PSU i just dont want to hook it up and see 10mv of differential noise and common mode shit everywhere if I spend that kind of money.

author: tautech
author_rank: Super Contributor
timestamp: July 05, 2024, 11:35:53 pm
content: Quote from: rwgast_lowlevellogicdesin on July 05, 2024, 11:25:22 pmBoth are stated on P4 in CV and CC modes:https://int.siglent.com/u_file/download/24_06_13/SPD4000X_DataSheet_EN01A.pdf

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: July 05, 2024, 11:43:59 pm
content: Ok so the 4000 looks pretty damn nice! The sheet says 5mV pk2pk ripple which is a bit more than the specs on the Keithley and measurable on a scope. The 4000s features are so much nicer than an old Kiethly though! It is a pretty PSU.

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 05, 2024, 11:46:56 pm
content: Quote from: rwgast_lowlevellogicdesin on July 05, 2024, 11:25:22 pmPersonally, I would choose between the Instek with LAN, or the 4000X series (but pay attention to specs- one opts for lower voltage and higher current).I don't recommend getting a used PSU. Get one with a fresh warranty.

author: Someone
author_rank: Super Contributor
timestamp: July 06, 2024, 01:20:06 am
content: Quote from: tautech on July 05, 2024, 10:30:43 pmSome competitors are using "typical" or "supplemental" specifications for the same, nice to see Siglent being a leader with guaranteed specs.