Bench power supply recommendation - Page 1
Forum section: electronics / testgear

author: thanasisk
author_rank: Regular Contributor
timestamp: March 26, 2020, 08:51:42 pm
content: Hi,I am researching the purchase of a bench power supply for powering low power uC projects and transistor/jfet/op amp designs for audio. My requirements are as follows:At least 3 fully isolated channels with current limitingVery low rippleTwo channels should have at least 15V output, no high output current requirementsSilent fan operation when idle and when not under heavy load (or fanless operation)Programmability for automated testingWell behaved outputs without nasty spikes or troublesome limitingSufficiently accurate low voltage and low current meteringNew products only as I do not have the capacity to repair or construct from scratchReasonable build quality (I see this as a long term investment)I am also wondering whether remote sensing terminals/4W would be of any use on such low current applications.I have found the Keysight E36312A, R&S NG103 and some AimTTI models from their PL series which tick most of the above boxes but some aspects above are not reported in their reviews online - and I would appreciate your ideas and experience.Budget is ideally below 1000E but if I want to stretch it even more I must be 100% confident of my choice.

author: nctnico
author_rank: Super Contributor
timestamp: March 26, 2020, 08:59:16 pm
content: The E36312A ticks all your boxes. There is a thread with several reviews:https://www.eevblog.com/forum/testgear/e36300-series-programmable-dc-power-supplies-(e36311a-e36312a-e36313a)/msg1233841/#msg1233841. The first batch had start-up issues but these have been recalled and fixed. I have a E36313A myself.Hopefully others will chime in with other options. The thread I linked to also contains some alternatives.

author: tautech
author_rank: Super Contributor
timestamp: March 26, 2020, 09:20:48 pm
content: 3 units SPD1000X, either the 15V or 30V model for a 750 Euro total.Good luck measuring the ripple on these, I've tried and it's down in the noise well under 500uV.Fits all your other requirements.

author: thanasisk
author_rank: Regular Contributor
timestamp: March 27, 2020, 04:16:19 pm
content: Thank you for your ideas.Unfortunately with 3 separate supplies there is no automated tracking (important for bipolar op amp configurations).I am following up with some questions specific to the e36300 in the relevant thread.Also looked at the gw instek gpp4323 which however has no remote sensing and according to a review by electrobob it is very inaccurate for low power (less than e.g. 10 mA).

author: Alti
author_rank: Frequent Contributor
timestamp: March 27, 2020, 06:34:04 pm
content: Quote from: thanasisk on March 27, 2020, 04:16:19 pmWhat if 3 supplies come with SCPI interface? It is a matter of executing the commands through SCPI in those cases where you require tracking.

author: tautech
author_rank: Super Contributor
timestamp: March 27, 2020, 06:54:42 pm
content: Quote from: Alti on March 27, 2020, 06:34:04 pmI suspect the capability of achieving 3 device tracking will hinge on the remote control software used but yes it's certainly worth researching more.The SDP1000X models use the NIVISA software for USB and LAN connectivity and do support a OUTPut:TRACk command.

author: nctnico
author_rank: Super Contributor
timestamp: March 27, 2020, 08:42:10 pm
content: Quote from: thanasisk on March 27, 2020, 04:16:19 pmOther PSUs in the same price range won't be more accurate than that.

author: apblog
author_rank: Regular Contributor
timestamp: March 28, 2020, 09:42:53 am
content: I have an E36313A and highly recommend it. It definitely won't disappoint. I assume the E36312A is similar. I especially like that it can measure current down to microamps.But it's a bit expensive and the logging is clunky.I also just picked up an AIM TTI PL303. It's quite nice, and the feature that lets you limit the voltage range is nice for safety. Personally I think I would have been happier with one of their all-digital models.i haven't really tested it yet for noise, ripple or spikes.

author: jpb
author_rank: Super Contributor
timestamp: March 28, 2020, 10:15:12 am
content: I have an E36313A as well as a TTi PL320QMD, a Keithley 2303 and a Hameg HM7042-5 and I use the last 3 all the time rather than the E36313A - this is not because the E36313A is not very good electrically, it is because it has a fairly noisy fan. Some people have replaced the fan in their units but I'm reluctant to do so as it is a fairly new unit but then I find myself not using it at all.Actually, the Keithley fan is pretty noisy as well, I did replace this which quietened it a bit. I use the Keithley when I want a very accurate current voltage measurement.My favourite is the TTi as it is totally silent, nice bright display which is pretty accurate and it was also the first supply I got so I'm rather fond of it!I should perhaps add that I don't use my supplies for logging or automated measurements - the TTi and the Hameg aren't capable of this anyway - I just use them as manual bench supplies.EDIT: I realise that I have an E3631A, not an E36313A SORRY - WRONG SUPPLY! (I wish Keysight/Agilent/HP would be less confusing with their numbering!)

author: nctnico
author_rank: Super Contributor
timestamp: March 28, 2020, 10:40:11 am
content: That doesn't sound right. The E36313A is very quiet for low power loads.

author: jpb
author_rank: Super Contributor
timestamp: March 28, 2020, 12:03:17 pm
content: Quote from: nctnico on March 28, 2020, 10:40:11 amI don't think it would be noticeable in a commercial lab or workshop, but in my home setup it sounds like a powerful desk fan - so not super loud but definitely noticeable.To be a bit more scientific I measured the noise level with it off ~40dBa about 30cm in front (with several other instruments on) and when I turn it on the noise level rises to 48dBa.It is probably a matter of individual sensitivity but I'm not the only one who finds it noisy:https://www.eevblog.com/forum/testgear/agilent-3631a/msg1042076/#msg1042076EDIT: I realise that I have an E3631A, not an E36313A SORRY - WRONG SUPPLY! (I wish Keysight/Agilent/HP would be less confusing with their numbering!)

author: nctnico
author_rank: Super Contributor
timestamp: March 28, 2020, 12:08:34 pm
content: Quote from: jpb on March 28, 2020, 12:03:17 pmI think we are talking about 2 different power supplies here. The E3631a is an older model (which could be loud since HP/Agilent didn't seem to care about noise at all in the old days). The newer E36313A is quiet. I can't hear it (except for the transformer humming every now and then) and I'm super annnoyed by test equipment making noise.

author: thanasisk
author_rank: Regular Contributor
timestamp: March 29, 2020, 03:14:56 pm
content: Quote from: nctnico on March 27, 2020, 08:42:10 pmIndeed. Any other recommendations for a power supply in the next price accuracy tier? It seems that the aim of more expensive equipment is always more Watts and Amperes and do not put much focus on accuracy at low currents (after having browsed through the R&S and AimTTI catalogues)

author: thanasisk
author_rank: Regular Contributor
timestamp: March 29, 2020, 03:19:35 pm
content: Quote from: apblog on March 28, 2020, 09:42:53 amI was initially considering the PL series but they have vent openings on the top so you cannot stack them without sufficient spacers (I suppose they were designed with specific rack cooling geometries in mind).I saw some short comments online that their all digital models (QL series?) have noisy fans.

author: thanasisk
author_rank: Regular Contributor
timestamp: March 29, 2020, 03:22:51 pm
content: Quote from: tautech on March 27, 2020, 06:54:42 pmWhile worth researching that means that a computer functioning as a controller must be used all the time and then you lose the simplicity and ergonomics of an all in one single physical knob solution..

author: nctnico
author_rank: Super Contributor
timestamp: March 29, 2020, 04:13:47 pm
content: Quote from: thanasisk on March 29, 2020, 03:14:56 pmTektronix (Fluke / Keithley) may have something in their assortment.

author: thanasisk
author_rank: Regular Contributor
timestamp: March 29, 2020, 05:10:10 pm
content: Quote from: nctnico on March 29, 2020, 04:13:47 pmThanx for the tips. Also read many complaints about the build quality and fan noise of Keithley supplies, perhaps someone can share their experience.(Btw. I am also thinking whether a combination of two supplies: a 2 output and a single output 30V with such accurate metering, would make sense in terms of total cost versus enabling the testing of most use cases.. any recommendation on as single supply with very accurate metering?

author: nctnico
author_rank: Super Contributor
timestamp: March 29, 2020, 06:31:12 pm
content: An older unit from Agilent is the 66311B (or one of it's brothers). It is near SMU capability but it needs a fan replacement; I have put a Noctua fan in mine to make the noise level acceptable. These can be found on Ebay for little money.

author: tautech
author_rank: Super Contributor
timestamp: March 29, 2020, 07:37:30 pm
content: Quote from: thanasisk on March 29, 2020, 03:22:51 pmYes however you do end up with a dedicated control for each channel.Just what the right solution for your requirements is not immediately apparent without a very deep pocket and the risk of a physically noisy installation. I do know from experience these units are quiet, electrically and fan too.And these are stackable.There's a thread about them here:https://www.eevblog.com/forum/testgear/new-spd1168x-siglent-psu/

author: pipe2null
author_rank: Regular Contributor
timestamp: March 29, 2020, 07:58:43 pm
content: Just a thought from a non-expert:If you're satisfied with the output regulation, but trying to get much higher accuracy/resolution of the measured output, perhaps you might consider the GPP-4323 or some other PS(s) plus a small stack of bench meters. Obviously it is not ideal compared to a clean all-in-one(or two) solution, but then your PS requirements would be somewhat uncoupled from your more restrictive measurement requirements. If you consider the GPP-4323, keep in mind the LAN option is factory installed only (China), but I think the USB is standard? I ordered mine w/LAN in February and I still have many more weeks to wait for delivery, not complaining though, they have a really good excuse for shipping delays. IF I recall correctly, and that is a big "IF", I thought ElectoBob's criticism was primarily about the measured output for display being one digit less accurate (basically, ignore the lowest digit), but that didn't have anything to do with the output settings or actual regulation.

author: nctnico
author_rank: Super Contributor
timestamp: March 29, 2020, 08:08:49 pm
content: If you add up the costs + bench space then getting a more expensive PSU is well worth it. Another problem is that DMMs have a high series resistance for current measurement. Last but not least the 66311B (which even has a high speed sampler to study power surge events) is the cheapest option by far.

author: tautech
author_rank: Super Contributor
timestamp: March 29, 2020, 08:19:33 pm
content: Quote from: nctnico on March 29, 2020, 08:08:49 pmYes well that depends on individual circumstances......say you have a 150mm slot on your bench or shelving.....perfect for stacking small PSU's.

author: apblog
author_rank: Regular Contributor
timestamp: March 29, 2020, 08:34:16 pm
content: Just get the E36312A. I have the E36313A, and it's fan is audible in my quiet office but not loud or bothersome.A good power supply is the foundation for everything else that you do. You don't want to be questioning your power supply or your brittle multi-supply setup every time something seems to be wrong with your circuit.Don't underestimate the value of convenience. Having it all in one unit, with metering built in, means you are free to focus on the fun parts of your hobby. And if you are pro, the high cost is well worth it for the productivity improvement.In my 30+ year career I have never regretted the purchase of a good tool. Usually I kick myself for not having done it sooner and having wasted money on junk.Also, call the dealer and see what they can do about the price. I got a couple hundred off the E36313A just for asking.Edit:Just saw colorado.rob's post. I'd be very tempted by the Aim TTI that he mentioned, it honestly seems like a better deal than the Keysight, if you think you might want more than 1 amp and don't care about very low current measurment.

author: colorado.rob
author_rank: Frequent Contributor
timestamp: March 29, 2020, 08:40:02 pm
content: I have an AIM-TTi MX100TP which I use when designing or working on battery-powered microcontroller circuits. I recommend it. The ability to go down to 0.1mA on the first channel is helpful. I use it with a Siglent SDM3065X to characterize power usage on circuits drawing under 1uA.It's not silent when under no load. It is still quieter than most of my other lab equipment. In fact, I only ever hear it when everything else is off.I do a lot of lab automation stuff. It has a good LXI interface. The monochrome display is a bit old-school, but it is fully functional and easy to read.

author: thanasisk
author_rank: Regular Contributor
timestamp: March 30, 2020, 01:29:11 pm
content: Thank you all for your recommendations!I could not get any significant discounts on the E36312A or the E36313A in Europe (the best price I was offered was around 1471E inc VAT and 1776E respectively). And keysight doesn't seem to have promotions on these products anymore (unless you know something)The MX100TP can be found for approx 900E at rapid (uk) and is so quite tempting.

author: thanasisk
author_rank: Regular Contributor
timestamp: March 30, 2020, 02:19:33 pm
content: Quote from: nctnico on March 29, 2020, 08:08:49 pmCan you compensate for this using remote sensing at the power supply?

author: nctnico
author_rank: Super Contributor
timestamp: March 30, 2020, 02:49:45 pm
content: Quote from: thanasisk on March 30, 2020, 02:19:33 pmI don't think so because the control-loop of the supply will be too slow to take care of narrow peaks. If you power a microcontroller through a DMM set to the mA range then a sudden change in current draw will make the supply voltage drop far enough to cause trouble.

author: thanasisk
author_rank: Regular Contributor
timestamp: April 02, 2020, 01:07:05 pm
content: Quote from: nctnico on March 30, 2020, 02:49:45 pmHave been thinking about this and wondering whether or not the bench power supplies with integrated metering actually suffer from the same problem. An integrated solution such as in the keysight E36312A I suppose pre compensates for the burden voltage of the internal shunt resistors but would the power supply auto ranging/meter shunt selection work fast enough were a sudden increase from nA current draw to 10ths of mA or vice versa were to occur?

author: alm
author_rank: Super Contributor
timestamp: April 11, 2020, 08:47:13 pm
content: The power supply will use something to limit the voltage drop across the shunt. Like a simple parallel diode, or this more elaborate solution that they used in the 66311B, which was a predecessor that had a similarly wide dynamic range for current measurements: