DC Programmable Load advice needed - Page 1
Forum section: electronics / testgear

author: sstepane
author_rank: Regular Contributor
timestamp: May 01, 2018, 11:11:53 am
content: Hi,I would like to ask for an advice on DC Programmable electronic loads since there's not much information or discussion on these. Sometimes there's not enough info even on manufacturers sites or in docs.I'm working with vaping devices and need to test these periodically, so I need robust and precise Constant Resistance mode. Vaping devices work with resistances from 0.01 Ohm to 1.5 (or a bit more) and are, actually, boost converters producing up to 300W (or up to 30-40Amp). It measures resistance before actually starting to sink current and use some frequency measurement involving a shunt resistor, INA199 amplifier and an ARm microcontroller.Why am I asking for an advice - because I've already tried couple of loads (Applent AT8612 and Rigol DL3012) and these do work occasionally - some devices do recognise the resistance configured, some - don't, sometimes the resistance is a bit off, sometimes - by a big amount off. I'm pretty sure - it has nothing to do with wirings (used remote sense and awg10 short wires), but rather with DC loads schematics and how they work. I should say that Applent's load did it much better than Rigol, but none of them was perfect. And this is what I'm looking for - fast CR mode response, precise and with some reasonable readout speed (at lease 1/10 second via usb or lan).Those loads are not that expensive to experiment with, but other brands are way more expensive and I don't want to end up with the same problem spending quite an amount.If anyone has some experience in this field - please advice me!

author: sstepane
author_rank: Regular Contributor
timestamp: May 03, 2018, 08:39:00 am
content: Hi,No replies. Either I'm asking something wrong or there's no experience available.I'll try from another point - which DC Load to choose - Chroma 63003-150-40 or BK Precision 8601 and why? Might there be someone experienced in this?

author: ogden
author_rank: Super Contributor
timestamp: May 03, 2018, 09:12:19 am
content: Quote from: sstepane on May 03, 2018, 08:39:00 amYou described what you want quite well. I bet there's no experience in lowresistancerange of DC loads, honestly I don't have such as well. Problem is that most DC loads are based on programmable current sink topology and CR mode is simulated using some analog feedback or what's worse - software. For vaping device which (somehow) probes resistance first, then applies load, such "emulated resistor" with limited response time could be problem. Limited speed of CR regulation is most likely source of problems you experienced.QuoteBK precision are good loads, no idea about Chroma. I can suggest Maynyo as good price/performance choice. I know that Maynuo M9712C in "usual" power supply testing CC mode works well. Make sure to have extra current handling capacity for your load. If you say that your source can put out 30 Amps, then you would want to get 60A-capable load, not 30A.Disclaimer: no idea how mentioned DC loads will work with vaping devices, sorry I would try to get load from reputable seller of testing gear, tell them my application - that I am interested in fast CR mode. Then I would have option to return instrument if it does not work.

author: BillB
author_rank: Unknown
timestamp: May 03, 2018, 11:02:32 am
content: Quote from: ogden on May 03, 2018, 09:12:19 amExactly this. I don't have any experience at the very low resistance level testing, but agree that the BK loads are decent. Depending on your interface requirements, that is if you don't need USB/GPIB, then you could look at the older series (8500). Maynuo and ITech are essentially clones of the BK for much less money, that work just the same.

author: sstepane
author_rank: Regular Contributor
timestamp: May 03, 2018, 11:16:09 am
content: ogden, BillBThank you very much for your replies - it is a bit clearer for me now - what to ask.Another questions - is Maynuo and Itech good clones? Since there might be even slight difference in reaction speed - a bit slower mcu/firmware from clones might be just enough to not work the way I need. Or there might be other mfg's with different resistance topology? (I think - hardly. DC Loads are not very common devices and its variety is even less probable).

author: ogden
author_rank: Super Contributor
timestamp: May 03, 2018, 12:14:42 pm
content: Quote from: sstepane on May 03, 2018, 11:16:09 amBoth are good. Do not consider those DC loads asclones. There's "white room" design approach and engineers happen to leave one company to get hired by another - you knowQuoteHard to tell. For < 1KW loads they all use more or less identical approach, even power stage circuits look surprisingly similarTry to carefully read specifications and/or contact "official distributor" in hope to get direct comment from manufacturer.You need DC load for characterization/review or repair purposes? Could you tell more what/how you are doing with vaping devices? I'm curious casual vaper / EEengineerconsultant

author: sstepane
author_rank: Regular Contributor
timestamp: May 03, 2018, 12:26:27 pm
content: Quote from: ogdenFrom what I see on web-sites (Maynuo and Itech) - there's barely some info and unknown software performance. Having experience with Rigol support - it's a dead end and for the moment I can afford something with a name on it and more-less reputable. So except for price - I see no advantages (Rigol has nice display and somewhat working software, but fails for this purpose a bit more than even Applent).Quote from: ogdenI do repairs/testing of devices for 1.5 yrs now. Actually - it's more a hobby. Learning electronics in practical way and, of course, such an equipment for this task is absolutely overkill, but I like to mess with it and I love nice equipment =) It warms my heart more than any kind of muscle car or whatever =)

author: BillB
author_rank: Unknown
timestamp: May 03, 2018, 12:37:29 pm
content: Quote from: sstepane on May 03, 2018, 12:26:27 pmYes, the Maynuo and ITech are from the same designer, but to meet a price point those brands do make some sacrifices, component-wise. There are a few tear-down videos showing some of the differences among them. With that said, I have a lot of experience with BK devices, and was a little leery of trying the ITech at first. However, as far as I'm concerned it works just as well, and for home bench use it's more than adequate for my needs.However, the software from most of the lesser Chinese brands is horrific. The ITech software is no exception, but it does work. As you said, theonlybenefit to selecting these over BK is price.

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 03, 2018, 02:28:23 pm
content: Have you seen my thread where I'm looking for a DC load? I don't have exactly the same requirements as you have, but the excellent suggestions of forum members do paint a fairly complete picture in regards to the available options. I'm currently leaning towards an Itech, as it has SCPI and four wire sensing.https://www.eevblog.com/forum/testgear/looking-for-a-dc-load/

author: PedroDaGr8
author_rank: Super Contributor
timestamp: May 03, 2018, 03:31:30 pm
content: Quote from: sstepane on May 03, 2018, 08:39:00 amChroma is a different ballgame and tier altogether normally. They make VERY high end loads, often used in heavy lab settings (many/most computer PSU manufacturers use Chroma loads to test the power supplies). Their loads are normally VERY well characterized and also cost a pretty penny. Most are designed for automated testing of some sort, so aren't always the most user friendly (they are industrial products).Quote from: sstepane on May 03, 2018, 11:16:09 amITech is not a clone, it is a subsidiary of BK Precision. The BK Precision loads are an ITech product with BK Precision badging according to whatBK Precision told Dave(not in those exact words).Maynuo is a clone, designed by the same engineer who was originally at ITech.Quote from: BillB on May 03, 2018, 12:37:29 pmITech is a subsidiary of BK Precision. So the software is likely nearly identical or 100% identical under the hood. The ITech and BK Precision loads are 100% identical electronically, as they are literally the same part with different badging. This isn't to claim exact identicallity. It appears that ITech constantly revises their products; my older ITech PSU has notably different internal parts from the modern version that is still sold. So versioning can result in apparent differences until the BK Precision model catches up.That being said, it is not correct to put them in comparison to the Array and Maynuo loads, which were designed by the same engineer but using the "white room" format, so they share a number of similarities but also notable differences.Also just as proof to quote theAbout Us page on BK Precisionsown website.Quote

author: sstepane
author_rank: Regular Contributor
timestamp: May 03, 2018, 03:39:06 pm
content: Quote from: PedroDaGr8 on May 03, 2018, 03:31:30 pmFunny, but in my country Chroma turns out to be on a par with BK Precision in price or even a bit cheaper. What I found interesting is that their load has CZ mode in which it is also possible to control capacitance of the load - with that a bit more precise lower values operations and controls I feel like it is the best solution among others. Overall, datasheet for Chroma is a bit more informative and precise of the other brands, but I have no idea what software (if any) is available for the load. I'd lean more on this brand, but have no idea what it is apart from what You've just said - no youtube or discussions or forums reviews...Quote from: Mr. Scram on May 03, 2018, 02:28:23 pmThanks, read it. Almost any decent load has sense terminals. That is a "must" for loads above 2-5A, I think.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: May 03, 2018, 03:47:38 pm
content: Quote from: sstepane on May 03, 2018, 03:39:06 pmI ninja edited my previous post. IMHO there is no comparison between the two in performance and quality. Chroma wins hands down, that being said as I said in my ninja edit, Chroma is industrial level quality and reliability. They do not aim themselves at the consumer market. This means you don't see them reviewed much or even discussed much by consumers. Unfortunately, that can also mean that documentation isn't always easily available unless you are a larger company. That being said, they are one of the gold standards for industrial loads. Especially for the ability to fully automate a full suite of test scenarios and just let it run. From what I have seen, most computer PSU manufacturers/OEMs use Chroma loads in their environment.

author: bicycleguy
author_rank: Frequent Contributor
timestamp: May 03, 2018, 09:51:01 pm
content: I am also investigating electronic loads for more general and multiple uses. The biggest question for me is which would be the best compromise for all the different things I want to do. Also how would the loads performance complicate or effect the DUT. It sounds like you have just one low voltage, high current task.Some kind of pure resistance setup would seem much better suited to what you want to do. Do you really need the flexibility, complication and unknown performance of an electronic load?

author: sstepane
author_rank: Regular Contributor
timestamp: May 03, 2018, 10:02:55 pm
content: Quote from: bicycleguy on May 03, 2018, 09:51:01 pmThis one task is critical, there are others (battery testing, for example). Also when it comes to the need of testing several different resistances for several devices pure resistance is getting a bit messy. And there's another issue with pure resistance to be tied to its temperature while the load is big. Plus documenting all in one go for resistances multiplied by devices.Overall this discussion opens a bit on poorly known/undocumented well low voltage range capabilities of loads. Especially if I will finally get some data from manufacturers.

author: nctnico
author_rank: Super Contributor
timestamp: May 03, 2018, 10:46:22 pm
content: You can also opt to built a DC load yourself using resistors which can be switched parallel or not. With a few standard values you can already create a wide range of resistance values. The advantage is that the load isn't compromised by the DC load's control loop behaviour and you can make really sharp load changes.

author: Deridex
author_rank: Regular Contributor
timestamp: May 05, 2018, 07:34:47 am
content: The Gossen K853A seems to have a low resistance range of 0.02 to 2 Ohms.It might be worth to take a look at.

author: 2N3055
author_rank: Super Contributor
timestamp: May 05, 2018, 07:55:50 am
content: Quote from: Deridex on May 05, 2018, 07:34:47 amThose are Array 372X series.. Gossen sells Array loads.. for 5x money..I have Maynuo 9812 and it works well.. PC software is surprisingly useful...

author: sstepane
author_rank: Regular Contributor
timestamp: May 23, 2018, 11:37:37 am
content: Hi there,After some investigation/discussion ordered GW Instek PEL-3031E.I have been trying to communicate with different makers and as a result - BK Prcision - take a closer look at the datasheet (approx. 1-1.5 week emails), Chroma forwarded to a local distributor and in the end told me that their load unlikely to be successful with the task (that took about 2+ weeks), Aim TTI never answered my email, and only GW Instek quite fast digged into my questions, once asked for clarification and told me that unlike some other load producers which use software method for Constant Resistance mode (load calculates required current) their loads use analogue loop detection, which should be as fast as possible. Furthermore, I can see that their manual and datasheet a bit more comprehensive on Current Resistance mode, how it works and its particular parameters (0.016 Ohm lowest range).Somehow I feel that GW Instek to Kikusui is somewhat like Maynuo to BK Precision...Hope this info will help others to make a decision in the future.I'll post info when the load will arrive and how it works in this task.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 23, 2018, 04:16:10 pm
content: Have you given any though about making something yourself?A bunch of cheap ceramic resistors, mounted to a heatsink (So they can be grossly overloaded pretty safely) combined with a bunch of relays and a uC, maybe some temperature measurement, cutout, fan regulator.The big advantage here is that you do not have to "simulate" a resistor. You have real resistors.

author: maukka
author_rank: Unknown
timestamp: May 23, 2018, 04:41:28 pm
content: Quote from: sstepane on May 23, 2018, 11:37:37 amThanks for the info. I tried to dig through the specs and manual but didn't find anything anywhere about a control software. Does it exist or do you have to program one yourself?

author: sstepane
author_rank: Regular Contributor
timestamp: May 23, 2018, 04:48:31 pm
content: Quote from: Doctorandus_P on May 23, 2018, 04:16:10 pmSure, but I don't have any spare time for the moment to start such a project.Quote from: maukka on May 23, 2018, 04:41:28 pmThis model does not seem to have anything except for the USB driver. Having seen software from other manufacturers I see the only option is to make my own. Visual Basic should do it easily. Interestingly - model PEL-3000 (kinda separate line) not only have some software but also commands compatible with Kikusui PLZ3 (I believe) load.

author: sstepane
author_rank: Regular Contributor
timestamp: June 18, 2018, 07:52:41 am
content: Hi,I thought if there anyone else interested in the subject - I would post some info. Finally received GW Instek PEL-3031E DC Programmable Load. So far it works in 90% of the cases with vaping devices. It is much more precise than Rigol.The fastest rate of readback I have been able to achieve via its USB(virtual rs232 in fact) using visual basic self-written simple app is about 2 readings per second. However, it was quite easy to write software for this device.I'd say its configuration is a bit awkward (via the front panel) and I did not try GW Instek trial software for it, but in other respects - this is very good device.Another interesting thing about it that it does switch 4 wire sense automatically when detects that it is connected.p.s. GW Instek tech support was friendly and really helpful, so I would say that this is also very important.

author: LaurentR
author_rank: Frequent Contributor
timestamp: June 18, 2018, 06:17:38 pm
content: Quote from: sstepane on June 18, 2018, 07:52:41 amThanks for the post sstepane. I am considering this load. It seems to be a interesting candidate in the 300W range.If you have more information, I'd be interested.Can you comment on the "awkward" front panel configuration?What about the trial software? I don't see any mention of it on the GW Instek page for the load.Also, is it quiet at low load?

author: sstepane
author_rank: Regular Contributor
timestamp: June 18, 2018, 06:40:05 pm
content: Quote from: LaurentR on June 18, 2018, 06:17:38 pmHi Laurent,Awkward - that is a bit unusual, but nothing to worry about. Navigating config section of the unit is a little bit unusual, but it is easy to get used to it and it is not that frequently used. Another strange thing is that even in static mode there are two values, say Value A and Value B, you can set both to a different value, but switching between them is done with "shift" key and is not that obvious - only small indication of what value is in effect right now. It is totally normal for dynamic mode or transition, but still unusual for simple static. But, on the other hand - may be even handy, like two profiles...Trial software is at the following link -http://www.gwinstek.com/en-global/Page/Link_ViewFrom the description it does things I don't need, so I didn't even checked it out. Somehow it is not mentioned on product's page, but is compatible. Visual Basic communication turned out to be quite easy and free, so it's my software option.Regarding its noise - it dusts fans at start. I did not put a lot of power for long time, but couple of 10 seconds 190W bursts didn't triggered its fans. On idle fan is like from Rigol DP832 PSU, may be just a bit lower.Other than that - I don't see anymore jumping resistance all around like it was with Rigol DL3000. In 90% it's simply there with no visible actions, and my devices I test report it very close to the one I've set, so from practical/experience for some 15+ devices right now it seems to be way more robust and precise dc load than Rigol or Applent. Well, but again, it costs twice more.If you have any questions - I'll gladly try to answer any.

author: GlowingGhoul
author_rank: Regular Contributor
timestamp: November 07, 2018, 08:31:39 pm
content: Quote from: LaurentR on June 18, 2018, 06:17:38 pmWorthwhile considering Chroma's 63000 series in the same price range:http://www.chromaate.com/product/63000_series_Programmable_DC_Electronic_Load.htm

author: LaurentR
author_rank: Frequent Contributor
timestamp: November 07, 2018, 08:38:39 pm
content: Quote from: GlowingGhoul on November 07, 2018, 08:31:39 pmI saw those but couldn't find anybody with advertised pricing. Do you know what price range they're in?

author: sstepane
author_rank: Regular Contributor
timestamp: November 07, 2018, 08:53:17 pm
content: Quote from: LaurentR on November 07, 2018, 08:38:39 pmI had a proposal for 63003-150-40 - 1380 euro. It's with local taxes/shipping/etc. But Chroma said that fast resistance response is not that good (I requested like 1 ms response) with the unit (might be the same system as with Rigol/etc - which sets resistance programatically via on-board software, while Instek declared that in their dc load it is wired with analog loopback, which is a lot faster).

author: GlowingGhoul
author_rank: Regular Contributor
timestamp: November 07, 2018, 08:57:10 pm
content: Quote from: sstepane on November 07, 2018, 08:53:17 pmI suppose if you have requirements for ultra-low resistance/fast response time scenarios, then the GW would be better suited, as in the case of vape development. For everything else, the Chroma is better.https://www.arrow.com/en/products/63004-150-60/chroma-systems-solutions-inc$1418, but after 10% off for first order with arrow, it's $1273 with free overnight shipping.

author: mightyohm
author_rank: Regular Contributor
timestamp: April 12, 2021, 08:40:00 am
content: Reviving an old thread.It sounds like there is a lot of variation in the response time between loads that operate in constant resistance mode using a software control loop vs. those like the Instek that close the loop in hardware.As far as I can tell, Instek doesn't advertise this feature.I'm shopping for an electronic load, and none of the loads I've looked at spec a response time or bandwidth for the constant resistance function. This seems like an important performance parameter and one that varies considerably between electronic loads, so why isn't this specified?

author: ogden
author_rank: Super Contributor
timestamp: April 13, 2021, 05:35:56 am
content: Quote from: mightyohm on April 12, 2021, 08:40:00 amIt's because usually MOSFETs are used as regulator for DC loads, making them essentially voltage controlled resistor. In constant resistance mode control loop does not regulate much, thus load have vitrually infinite response bandwidth.