Bench Power Supply - Page 1
Forum section: electronics / testgear

author: Majorbob
author_rank: Regular Contributor
timestamp: November 28, 2020, 08:53:46 pm
content: Hi all, sorry if this is the wrong place,I'm wanting a bench power supply for xmas. Ideally I'd like dual channel, up to 30V, up to 5A and linear. I've scoured ebay for second hand ones and it seems to be very thin on the ground. Budget is quite low, I'd like to keep it under £100 if possible. And I'm in the UK. Can anyone shed any light on my search? Most of what's on ebay seems to be low-quality chinese crap.Thanks.

author: Jeroen3
author_rank: Super Contributor
timestamp: November 28, 2020, 10:34:23 pm
content: Quote from: Majorbob on November 28, 2020, 08:53:46 pmYes, sad times. Turn on "used" for the good brands. There are some HP's on it now.Although, the Korad K3005 ones and rebrands are good enough for their price I would say.Best of the worst,I guess.

author: de_light
author_rank: Regular Contributor
timestamp: November 28, 2020, 11:57:57 pm
content: I have a Wavecom PS-3005D (Korad rebrand) SMPSUPretty happy with this for the price.Did a quick scope of the unloaded power supply at the output set to 9V.20M filter on

author: radiolistener
author_rank: Super Contributor
timestamp: November 29, 2020, 11:42:54 am
content: Yes, KORAD KA3005D is the best choice for a universal lab PSU.But don't expect very clean output, it has a little noise. Probably from dynamic LED indication.Pulse appears with about 120 Hz (8.3 ms) period and consists of about 34 MHz oscillations

author: tggzzz
author_rank: Super Contributor
timestamp: November 29, 2020, 11:49:22 am
content: There are a couple of Ramco auctions coming up, with many PSUs. Some of those might meet your needs, and hence be worth considering - but don't bid too high!There's no guarantee with any of the items, so you have to look at the photo carefully and take a chance. Usually, but not always, it is OK.They ship for £15. Don't forget to add 15.5% and 20% to the hammer price!

author: nctnico
author_rank: Super Contributor
timestamp: November 29, 2020, 08:38:06 pm
content: Quote from: de_light on November 28, 2020, 11:57:57 pmDave did a teardown of the Korad KA3005P PSU which looks similar to the PS-3005D.At least this isn't a switching PSU.I Strongly recommend against a switching power supply for doing electronics development because of the noise they can/will inject into your measurements. Don't get me wrong here; switching PSUs are great for delivering lots of power but not for use as a primary bench supply while making (sensitive) measurements.

author: Majorbob
author_rank: Regular Contributor
timestamp: November 29, 2020, 09:10:44 pm
content: Linear is the only way to go in my view. The Ramco auction was a great shout, seen some great power supplies on there and hoping to win an Metrix AX503.

author: tggzzz
author_rank: Super Contributor
timestamp: November 29, 2020, 09:30:00 pm
content: Quote from: Majorbob on November 29, 2020, 09:10:44 pmMake sure you are registered well before the auction starts. That process is not instantaneous.See also the Peaker Pattinson auctions, but beware that at Aunby they store some stuff in a farm barn.There will be another auction along soon, with more PSUs

author: nctnico
author_rank: Super Contributor
timestamp: November 29, 2020, 09:46:39 pm
content: Quote from: Majorbob on November 29, 2020, 09:10:44 pmThat Metrix AX503 doesn't look very compelling to me. Voltage is shown with 1 decimal only. That is pretty much useless for electronics work.

author: uski
author_rank: Frequent Contributor
timestamp: November 29, 2020, 11:59:43 pm
content: Quote from: nctnico on November 29, 2020, 09:46:39 pmI wouldn't say that... many people just need a stable 5V or 12V with some intermediates in between, sometimes.And with a 100 GBP budget, you can't do miracles.I would focus on getting a linear PSU with a stable and low-ish noise output.Then, you can add an external voltmeter. My concern is more about current display, I like to get a precise measurement of the current. But again that can be done externally.I got myself a Keithley 2280S PSU... 6.5 digit readings straight from the PSU. It's maybe too much. I have an Agilent which reads only 2 digits and I found it is not enough especially for the current.So a reasonable ground is probably 3 decimals (i.e. down to the mA) and most cheap PSUs don't do that (but there are optons, see my post below). Adding an external meter is probably the way to do it cheap.

author: uski
author_rank: Frequent Contributor
timestamp: November 30, 2020, 12:06:51 am
content: OP, please consider that your instrument will probably last you for a decade or more. At least that's the experience I have with my instruments.So it makes sense to "invest" a bit, if you can afford it at all.With that in mind, have you considered a Siglent PSU such as theSPD3303X-E?It is around 300 GBP. You can parallel the 2 outputs for up to 6.4A, or put them in series for up to 64V.Seems like a very capable power supply, that would probably last you for a while. And having 2 outputs is very useful and it also has a third 2.5/3.3/5V output which is convenient.There is also theSPD3303Xwhich is sigificantly more expensive, for a higher resolution reading (1mV/1mA instead of 10mA/10mV on the -E)Some people have hacked theSPD3303X-Eto become aSPD3303X. If you are really on a budget, that could be an option...Rigol also makes theDP832for instance, I had one and didn't really like the user interface, but it is an option. More expensive however. Can be hacked too.You know the saying "poor people pay twice". You are probably going to put 100 GBP in a power supply, and unless you are able to find a bargain (which I hope you do !), you might end up buying another more expensive one in a year or two.Finally... used instruments are fun... but sometimes it is frustrating to spend more time fixing the instrument itself than working on your projects, especially if it is your primary instrument and you don't have another one. Most of the time you can fix it but sometimes you can't and it's frustrating. Getting a new instrument will ensure that you get an instrument you can rely on. I know this from experience, my very first power supply was faultly. I was a student at the time and got a brand new one for christmas... but it was a cheap one... and it was real crap. Now I could afford an expensive power supply and that's what I did. No regrets. So take a look at these Siglents units

author: radiolistener
author_rank: Super Contributor
timestamp: November 30, 2020, 12:16:35 am
content: Quote from: nctnico on November 29, 2020, 08:38:06 pmYes, it has very low noise, much better than very good SMPS. But you can catch some rare small pulses, see my picture above. These pulses are always present on the output even when output is OFF. It disappears when you power off PSU. I didn't find this noise on the spectrum, but you can catch it with oscilloscope. I suspect it comes from the dynamic indication of 7-segment LED.The LED indicator is very bright, so I'm thinking about reduce LED brightness. Does anyone tried to reduce brightness?

author: uski
author_rank: Frequent Contributor
timestamp: November 30, 2020, 12:21:26 am
content: Quote from: radiolistener on November 30, 2020, 12:16:35 amHave you done your measurement with any load on the output ? I suspect it could be very high impedance noise. Still not perfect, but it's likely your lab has electrical noise from other things.In addition if the oscillations are 34MHz, they should be easy to filter out by adding a small LC filter on the line.But I wonder if it is not oscillation or ringing in your probing setup.

author: Stray Electron
author_rank: Super Contributor
timestamp: November 30, 2020, 12:25:55 am
content: Quote from: Majorbob on November 28, 2020, 08:53:46 pmGo to Ebay and put in your location and then search for HP or Lambda or other GOOD quality power supply, then tell E-bay to only show USED items, then tell E-bay to show the nearest ones first. Find one that you want and ask the seller if they will allow local pickup (and not charge for it). Find one that you like, buy it and then go pick it up. Used power supplies don't sell for much on Ebay, particularly linear supplies because they're so heavy to ship, so buy one locally and save yourself a ton of money. I recommend the HP supplies because they're GOOD, they're reliable and service info is available for most of them. But choose what you want.PS Don't waste your time on some of the ridiculous priced items on Ebay. I start with the lowest priced items and then work my way up to the higher priced ones until I find something that will do what I want. Buy USED only, don't waste you time on anything non-working unless service manuals for it are available and you WANT a challange. Or buy NEW, but be ready to pay the price!If you don't find a suitable one right away, you can save the search and have E-bay E-mail you when one shows up.I typically pay between $10 and $20 for olderworkingHP supplies. If you want one with digital displays, expect to pay considerably more but they won't work any better than an old linear supply with analog meters. I have HP supplies from the 1960s that still work fine. One of the nice thing about the HP supplies is that they used GOOD capacitors and I've never seen a cap fail in one.

author: radiolistener
author_rank: Super Contributor
timestamp: November 30, 2020, 01:38:21 am
content: Quote from: uski on November 30, 2020, 12:21:26 amIt was measured through 1 meter coax cable RG58 with BNC connectors and BNC to banana adapter. There is no load. When I short output terminals with 1 meter cable it doesn't affect this noise. Output ON/OFF also doesn't affect this pulse.It looks like a little interference from dynamic LED refresh currents. Because when I power off PSU, the pulse disappears.I tried to connect the same cable to HY1505D PSU and there is no pulses.On the radio receiver, I don't see any noise on 34-35 MHz.Just tested KORAD KA3005D and HY1505D output with soundcard input and it looks that KORAD has less noise floor. But it has some noise at about 600 Hz with about -90 dBm (soundcard input is calibrated with 50 Ohm generator).The first screenshot is KORAD KA3005D output spectrum (the switch moment is pressing ON button).The second screenshot is HY1505D output spectrum (the switch moment is putting BNC-banana adapter into PSU).Both PSU are configured for 1.0 V output.

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2020, 09:14:31 am
content: Quote from: uski on November 29, 2020, 11:59:43 pmBut you don't know whether 5.0 is actually 4.9 or 5.1 by definition. Nowadays lot's of circuitry works on much lower voltages where 0.1V makes all the difference.

author: radiolistener
author_rank: Super Contributor
timestamp: November 30, 2020, 09:41:32 am
content: I don't use 5V, almost all my circuits working from 3.3VMicrocontrollers, modules - almost all needs 3.3 V.The main goal for 5V is to feed 3.3 V regulator.

author: Datman
author_rank: Regular Contributor
timestamp: November 30, 2020, 11:03:20 am
content: Why do you need a dual supply? Do you really need high current on the negative voltage?...If not, you could buy two different power supplies beginning from the one you need more. They could be a primary powerful one and a secondary little one for negative voltages or other, i.e. 0~15V 500mA. The secondary one could also be a dual 0~15V 500mA.For 5V and 3.3V you could use a common USB PS, a USB cable and a little box with a simple filter (a common-mode coil salvaged from an old CFL lamp and a capacitor) and an integrated low drop 3.3V regulator.

author: nctnico
author_rank: Super Contributor
timestamp: November 30, 2020, 12:06:51 pm
content: Quote from: Stray Electron on November 30, 2020, 12:25:55 amI prefer digital meters. With analog meters I usually pull out a DMM to check the voltage. It might be worth checking out how accurate the meters on the Korad supply are. Recently I bought a bunch of Gophert PSUs (these are switching ones) from Aliexpress but their meters are shockingly accurate. Especially given the price.QuoteI'd check the wiring in those. Especially when wires are soldered into boards directly. Over the years I have owned several older HP power supplies and in some I could pull the wires from the boards. Two of them needed replacing the electrolytics. In other words YMMV and I wouldn't recommend someone buying such old supplies.

author: Yansi
author_rank: Super Contributor
timestamp: November 30, 2020, 03:57:58 pm
content: Quote from: nctnico on November 30, 2020, 12:06:51 pmThe Korad voltage meter/preset is and was almost spot on on all PSUs I've put my hands on. If you set i 5.000, you can bet you'd be where you need to.The current meter is a completely differet matter, but one does not expect much accuracy there, right?

author: Electro Fan
author_rank: Super Contributor
timestamp: November 30, 2020, 04:26:21 pm
content: I have found the Korad to be be consistently accurate on voltage and current. If you ever need it there is a calibration routine that is accessible with the outside controls (no need to open the power supply). I made some very small calibration adjustments when I purchased the PS years ago and it continues to perform consistently and reliably. After accumulating a TEA-worthy bench full of test equipment I would have to say that the Korad KA3005P is very possibly the best value on my bench when I consider how often each piece of equipment is used along with how accurate, reliable, and enjoyable it is to use, plus what it cost. If you don’t need the computer control feature I’m sure the same or even better could be said about the KA3005D - in fact it’s probably an even better value and arguably one of the best values among not only linear power supplies but among any entry level piece of test equipment you can buy new for about $110.

author: Yansi
author_rank: Super Contributor
timestamp: November 30, 2020, 04:44:12 pm
content: But beware, there were many different versions of the very same Korad supply. For example, at least one of my units came with Nippon Chemicon capacitors - I have no idea how that happened. Others reported cheap material PCBs n the power section - I have green standard FR4 there.Also, in the past, some of the early units had wrong or incorrect power transistors mounted, so the supply could easily die.

author: masterx81
author_rank: Frequent Contributor
timestamp: November 30, 2020, 05:03:52 pm
content: I have the Korad ka3305p dual psu, spot on. Not precise at the very milliampere, but it's good enough for most uses.Take always in mind that this type of psu have some capacitance at the output. Never "hot connect" something. Use always the on/off button.

author: Yansi
author_rank: Super Contributor
timestamp: November 30, 2020, 05:37:14 pm
content: Well, you can "hot connect", but you need to be aware of what may happen.Cranking the PSU to 30 V (or even much less) and setting the current limit to 10 mA to test a LED hot connecting it, will definitely blow shit up.Also, using the output on/off button is a good practice anyway.

author: Majorbob
author_rank: Regular Contributor
timestamp: November 30, 2020, 06:34:16 pm
content: A few comments to reply to, sorry but I'm not going to add in multiple quotes.At the moment only having 1dp isn't a massive issue and not a big concern, as someone else says I can use a separate voltmeter to get more accuracy (and I'm not adverse to adding a voltage divider if finer adjustment is required)The PSU is going to be an xmas present (hence the limited budget). If my usage of it increases greatly then I'll invest in a brand new supply with more programming abilities etc.Searching ebay has shown very few PSUs available in the budget that fit my requirements at all.Thanks for the help and suggestions, this thread will definitely be referred to if/when I'm looking at upgrading.Edit:I did look at separate single supplies for the same job as a dual, but with the cost and functionality of the one I've chosen I've decided going for 2 singles isn't worth the worry.I try not to hot-connect where possible at any voltage or current.

author: Electro Fan
author_rank: Super Contributor
timestamp: November 30, 2020, 07:41:31 pm
content: fwiw,Here is a current measurement showing a Korad KA3005P reading as it powers a simple DUT vs readings from an Aneng 8008, a Fluke 179, and a Keysight 34465A. (They were all strung together in a circuit.)Edit: a couple observations. 1) I think the Korad is good to within about a milliamp, 2) might have to tune up the 34465A(To be square, I think by the time I got to the 34465A the current had been drifting/settling slightly downward which pulled the average down a tad - but now we are talking about my ever changing air conditioned temperature and we are getting into volt nut, temp nut, etc nut territory.) Bottom line: If you want a power supply and your budget is ~$100, just buy a Korad KA3005D and keep moving toward whatever your goal might be.

author: radiolistener
author_rank: Super Contributor
timestamp: December 01, 2020, 09:07:13 am
content: Quote from: nctnico on November 30, 2020, 12:06:51 pmHere is my test for KORAD KA3005D from another thread:Unloaded output.Format is [setting voltage] = [measure output]:0.10 V = 0.10159 V0.50 V = 0.49860 V0.70 V = 0.69990 V1.00 V = 0.99695 V1.01 V = 1.00594 V1.20 V = 1.19851 V2.00 V = 1.99745 V3.00 V = 2.99477 V3.20 V = 3.19320 V4.00 V = 3.99448 V5.00 V = 4.99893 V6.00 V = 5.99988 V7.00 V = 6.9970 V8.00 V = 7.9970 V9.00 V = 9.0025 V10.00 V = 9.9969 V11.00 V = 11.0012 V12.00 V = 11.9992 V13.00 V = 12.9997 V14.00 V = 14.0037 V15.00 V = 15.0026 V16.00 V = 16.0053 V17.00 V = 17.0020 V18.00 V = 18.0143 V19.00 V = 19.0084 V20.00 V = 20.0103 V21.00 V = 21.0092 V22.00 V = 22.0081 V23.00 V = 23.0159 V24.00 V = 24.0120 V25.00 V = 25.0161 V26.00 V = 26.0132 V27.00 V = 27.0226 V28.00 V = 28.0181 V29.00 V = 29.0227 V30.00 V = 30.0234 V31.00 V = 31.0211 VLoaded output test.Format is [voltage setting] => [measure unloaded voltage] / [measure loaded voltage] @ [measure load current]3.20 V => 3.19293 V / 3.17939 V @ 4.138 A5.00 V => 4.99890 V / 4.98319 @ 4.803 A9.00 V => 9.0027 V / 8.9877 V @ 4.630 A12.00 V => 11.9991 V / 11.9808 V @ 4.703 A19.00 V => 19.0084 V / 18.9909 V @ 4.798 A24.00 V => 24.0118 V / 23.9928 V @ 4.751 A30.00 V => 30.0231 V / 30.0025 V @ 4.809 AMeasurement is done with Brymen BM867S.KORAD allows to perform calibration. And I done precise calibration when I bought it.

author: radiolistener
author_rank: Super Contributor
timestamp: December 01, 2020, 01:44:48 pm
content: KORAD KA3005D current measurement and stabilization test.Format: [current setting] => [multimeter measure current] / [KORAD measure current]0.001 A => 1.540 mA / 0.000 A0.002 A => 2.744 mA / 0.000 A0.005 A => 5.992 mA / 0.003 A0.010 A => 10.860 mA / 0.009 A0.015 A => 15.858 mA / 0.014 A0.020 A => 20.631 mA / 0.019 A0.030 A => 30.434 mA / 0.028 A0.040 A => 40.916 mA / 0.038 A0.050 A => 50.704 mA / 0.049 A0.100 A => 100.75 mA / 0.099 A0.150 A => 150.30 mA / 0.148 A0.200 A => 200.86 mA / 0.199 A0.250 A => 250.98 mA / 0.249 A0.300 A => 300.59 mA / 0.298 A0.350 A => 350.47 mA / 0.349 A0.400 A => 400.59 mA / 0.399 A0.450 A => 450.05 mA / 0.448 A0.500 A => 500.62 mA / 0.499 A0.550 A => 0.5507 A / 0.549 A0.600 A => 0.6003 A / 0.599 A0.700 A => 0.7009 A / 0.699 A0.800 A => 0.8019 A / 0.800 A0.900 A => 0.9014 A / 0.900 A1.000 A => 1.0024 A / 1.001 A1.500 A => 1.5026 A / 1.500 A2.000 A => 2.0012 A / 1.999 A2.500 A => 2.5024 A / 2.500 A3.000 A => 3.0031 A / 3.000 A3.500 A => 3.4987 A / 3.498 A4.000 A => 3.9991 A / 3.998 A4.500 A => 4.5016 A / 4.500 A5.000 A => 5.0005 A / 4.999 A5.100 A => 5.1007 A / 5.100 ABought this unit almost year ago for about 80 USD include shipping costIn comparison with Dave teardown video, my unit is almost the same. But there is a difference for power regulator module. Heatsink is now more massive with better transistors mounting.

author: Yansi
author_rank: Super Contributor
timestamp: December 01, 2020, 03:08:00 pm
content: That is some of the very newer designs. Mine is much older, also has three snap-in caps in parallel. The photo is from January 2014, when I've bought my second Korad PSU and was modifying the hilarious heatsink for a proper one, so the fan can shut the fuck up.Also I've never done any calibration to any of my Korad PSUs, would be interesting to test, have a calibrated 34401 available now so...

author: tooki
author_rank: Super Contributor
timestamp: December 01, 2020, 03:47:20 pm
content: Quote from: Yansi on December 01, 2020, 03:08:00 pmI really need to do that. I put a better, quieter fan in, but the janky heat sink makes it moot.

author: Croby80
author_rank: Newbie
timestamp: December 01, 2020, 07:58:27 pm
content: Hello, I'm looking for a good (but not expensive) power supply unit for my personal laboratory and I'm observing by long time the following model on aliexpress store:https://it.aliexpress.com/item/1005001615696493.html?spm=a2g0o.cart.0.0.5a3d3c00R6iaCI&mp=1it is a single channel 300W programmable power supply with a declared accurancy of 0,01mA for current and 0,1mV for voltage with capability to record and graphically visualize voltage current and power . It is possible to define 100groups of timed programmed steps and also to manage battery charge slopes. RS232, analog and USB interface are available (LAN optional) to be conneted to a PC to remotly control and to visualize V,I,P,R parameters. Sense compensation is another feature with a 4,3" rgb graphical display. Price = 511euros.Brand is AB-F but I suppose could be a rebrand for eTommens manufacturer:http://www.etommens.com/dgweb_content-847183.htmlAnyone has experience with these devices? What do you think about that?(I attached datasheet of previous 5 digit version =0,1mA, 1mV)Thank you

author: tautech
author_rank: Super Contributor
timestamp: December 01, 2020, 08:15:26 pm
content: Quote from: Croby80 on December 01, 2020, 07:58:27 pmJust what are your real requirements ?Precision or raw power ?

author: Yansi
author_rank: Super Contributor
timestamp: December 01, 2020, 08:56:04 pm
content: Quote from: tooki on December 01, 2020, 03:47:20 pmThe original fan is quiet enough, if you put a resistor in series. I gues it was something like 33 or 39 ohms, what I've added there.//EDIT: 68ohms, according to my photos.

author: Yansi
author_rank: Super Contributor
timestamp: December 01, 2020, 08:58:52 pm
content: Quote from: Croby80 on December 01, 2020, 07:58:27 pmFor abotut the same price you can get a second hand 300W HP/Agilent PSU. This I'd never pay so much for, especially if it's something noname, and likely a switchmode noise transmitter.

author: Elasia
author_rank: Frequent Contributor
timestamp: December 01, 2020, 08:59:35 pm
content: I've been looking at this 1800W A-BF... only reason i havent bought it is because I fear burning the house down with ithttps://www.aliexpress.com/item/4001126735505.html?spm=a2g0o.productlist.0.0.5e891a6f9Q3V1a&algo_pvid=99b7ccc9-cb97-4a59-8de1-e2ca6a5ae7a4&algo_expid=99b7ccc9-cb97-4a59-8de1-e2ca6a5ae7a4-4&btsid=0bb0623216068558525863252ed93f&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_Any news with what Siglent is doing with that 5000 series yet tau? Been eyeballing one of those but seems like a year wait

author: nctnico
author_rank: Super Contributor
timestamp: December 01, 2020, 09:32:21 pm
content: Quote from: Yansi on December 01, 2020, 08:58:52 pmBut not a high precission one. With a weight of 7kg it seems to me there is a regular transformer inside these power supplies with a linear power stage. I don't think you can get the low noise and accuracy from a switcher so it has to be linear. Or at least have a linear power stage behind a pre-regulator.Quote from: Elasia on December 01, 2020, 08:59:35 pmYou can also look for a Gophert PSU. These seem to have a good track record.

author: tautech
author_rank: Super Contributor
timestamp: December 01, 2020, 09:53:09 pm
content: Quote from: Elasia on December 01, 2020, 08:59:35 pmNuthing to report as I've not asked but will today and post anything of interest in the SPS5000X thread.

author: Datman
author_rank: Regular Contributor
timestamp: December 02, 2020, 09:53:46 am
content: I have an ATTEN APS3005Si. It a linear PS (no switching noise at the output). I have replaced the 4 pots with 2 multi-turn, added a thermostat and a resistor and a trimmer to adjust Ammeter offset. I have replaced the 470uF output capacitor with a 10uF one, avoiding current peaks in CC mode.Look at this thread:https://www.eevblog.com/forum/reviews/atten-aps3005si-pots-replacement-and-meters-adjustment/

author: Croby80
author_rank: Newbie
timestamp: December 02, 2020, 08:03:26 pm
content: I need an accurate PSU with almost 200W of power. I attched the internal power supply composition, I suppose it could be a switching + linear regulation method as declared by custumer for the previous less accurate model SS-L3010SPL (about 360 euros).

author: tautech
author_rank: Super Contributor
timestamp: December 02, 2020, 08:17:12 pm
content: Quote from: Croby80 on December 02, 2020, 08:03:26 pmIs 150W enough ?https://www.siglenteu.com/power-supplies/spd1000x-series-programmable-dc-power-supply/

author: Croby80
author_rank: Newbie
timestamp: December 02, 2020, 08:26:39 pm
content: Better 200W, one single output is not a problem

author: Croby80
author_rank: Newbie
timestamp: December 02, 2020, 08:44:25 pm
content: I'm comparing DP832 vs SPD series programmable supply, I see Rigol is more accurate respect to Siglent device but more expensive. I also seen that Rigol is able to generate prefixed output waveforms such as sine, ramp or steps defining their characteristic parameters: are these waveform completely analog or discrete? I mean, the 2048 (V,I) samples sets of Rigol define the maximum resolution of the output waveform?

author: Yansi
author_rank: Super Contributor
timestamp: December 02, 2020, 08:48:44 pm
content: Quote from: Croby80 on December 02, 2020, 08:03:26 pmClearly tthere is no switchmode pre-regulator, instead, in the bottom part of the photo, there are two relays marked as "group switching" (selecting the secondary voltage from 4 possible configurations).

author: tautech
author_rank: Super Contributor
timestamp: December 02, 2020, 09:22:18 pm
content: Quote from: Croby80 on December 02, 2020, 08:44:25 pmWhich model ?These ?https://www.siglenteu.com/power-supplies/spd3303x-spd3303x-e-series-programmable-dc-power-supply/

author: uski
author_rank: Frequent Contributor
timestamp: December 03, 2020, 10:32:48 am
content: Quote from: Majorbob on November 30, 2020, 06:34:16 pmWhat? If you think about a resistive voltage divider at the output, you most likely cannot do this due to the equivalent source impedance. Or were you referring to adding a separate potentiometer to the existing potentiometer for finer voltage adjustment ?Quote from: Majorbob on November 30, 2020, 06:34:16 pmThis is exactly how I got my first sh*tty power supply that I regretted purchasing.My parents bought it for my as a christmas present years ago.I'm not saying to buy something expensive, but please do yourself a favor and buy something good. See my suggestions for the Siglent PSUs.Remember, these instruments will last you for years. It makes sense to invest a bit more in the beginning and have a good instrument from the beginning, instead of suffering from a poor instrument and then having to pay for a better one later anyway. I'm trying to save you from disappointment that I experienced in very similar conditions years ago.Specifically the one I had had horrible regulation characteristics where it could not setup the current limit down to 0, there was a dead band between 0 and 200mA or so, and also, at these voltages, the voltage output changed suddenly around the current limit setting. I hated that power supply !!!An alternative if you are cash strapped is to buy a single but good quality power supply, and then make yourself an adjustable power supply with an LM317 regulator. It's a fun project, it will be cheap, and there will be many situations where you will not need much power, for instance when powering digital circuits. Or go fancy with a UA723 and add current limiting and so on.PS: regarding the Siglent PSUs, they can be hacked to get more precision, if you are really cash strapped. SPD3303X-E with 10mV/10mA precision can be hacked to a SPD3303X model with 1mA/1mV. Not commenting on the ethics/legal/warranty aspects of that modification, it's a tradeoff you have to consider yourself. But in my view, a hacked SPD3303X-E is infinitely better than a crappy PSU.

author: Croby80
author_rank: Newbie
timestamp: December 03, 2020, 06:00:14 pm
content: Yes, the SPD3303X model

author: tautech
author_rank: Super Contributor
timestamp: December 03, 2020, 06:05:31 pm
content: Quote from: tautech on December 02, 2020, 09:22:18 pmQuote from: Croby80 on December 03, 2020, 06:00:14 pmThen you need study what uski wroteQuote from: uski on December 03, 2020, 10:32:48 am