ARRAY electronic loads

[saturation]

It certainly can be, but I think these folks try, and IMHO honest opinion is worth more than hype from the manufacturer.  But, I'm not as obsessed with PSU power supplies as these folks, so I leave that criticism for another thread!

For our needs however and this thread, it appear like a good torture test of Array's lower  cost electronic loads, that link is strong suggestion that Array's can hold up.  Further, the demands of the design suggests the author knows what he's doing, technically, and is putting his money where his mouth is,  the setup cost €10,835, €4,500 is just for the 10 Array loads alone.

http://www.techpowerup.com/articles//overclocking/psu/161/4

I emailed the author, and he's been using the test setup up for > 1 year.   If you read how he tests it, regardless of the PSU, he's pushing the 3710 and 3711 to the limits of their power capacity, so as a e-load, its durable and reliable.

That said he also mentions a key flaw, that are corrected in Array's newer and more costly models, 372x series: it has no remote sensing, so beware voltage drop on the leads at higher loads.

I also noted on the manuals and reading the 372x manuals, the 3700 series slew rate, i.e., amps/microsecond, cannot be programmed.   You can program automatic periodic load changes, e.g. cycle from 1A to 0.1A ~  per second increments, but you are at the mercy of the units inboard switching to determine the rate of change. 

That was my gripe with 95% of the Tech websites PC PSU reviews, largely inaccurate measurements

[MikeO]

Hello all,

I came across this thread while googling for a manual for a Kikusui PLZ300W electronic load.  I need an electronic load for a project I took on, and am on a tight budget.  I looked at the Array units and they seem nice.  I ended up buying the PLZ300W, on ebay, for $360US, including expedited shipping.

My main reason for making this choice was budget, and, in a previous life, I shared an identical unit with a couple of engineers and a couple of techs.  I was in that lab for ten years, and that load was no spring chicken when I got there.  It performed flawlessly for all the time I was there, and it was in high demand (lab was engineering department for a battery and charger manufacturer).

I didn't over-think it, and went with what I know.  I doubt it has the features many of you seek, but, as far as dependability and accuracy per dollar, it's a worthy consideration (if buying used).

I think we all love new gear, but I've been so burned by Chinese made goods, I generally do what I can to avoid them.  It may seem racist but, really, I've thrown away A LOT of Chinese made tools; frankly, I think there is some cultural differences, and they do not embrace the meaning of the word "quality" in the same way.  Regardless, I did just buy that 1052E.

I don't do much engineering these days, but have this one job, and need to set up a mini lab at home.  I'm trying to do it for under $1000US, so as not to suck all the profit out of the job.  I bought a Rigol 1052E direct from the manufacturer, two HP bench supplies (6289A, 6291A), and the PLZ300W, and, so far, with shipping, I've spent $833US.  I still need a simple, low-speed function generator, and an array of test leads, but I think I'll make my budget.  Considering that I've not been watching ebay for good prices, let alone hit up the HAM radio folks, but rather selected and purchased these items today, at the "buy it now" premium, I think one could do even better.

Anyway, my point is, 30 year old equipment doesn't tend to inspire confidence, and usually lacks great, modern features, but the old thru-hole gear is very dependable and very repairable.  Best of all, you can choose quality levels you couldn't otherwise get into the budget.  The one caveat is the dark years of electronics: the previous decade.  When Europe introduced the RoHS and WEEE legislation, it all really went bad.  The lead free solders, tin whiskering, delaminated PCBs (from the higher heat for new solders) made for some of the worst lived electronics in the history of, well, electronics!  I avoid gear from that era, whether it be an electronic load, or a car stereo.  You can keep it

So, there are some opinions from some random guy on the internet.

Best of luck in your endeavors.

Regards,
Mike O'

[EEVblog]

I think we all love new gear, but I've been so burned by Chinese made goods, I generally do what I can to avoid them.  It may seem racist but, really, I've thrown away A LOT of Chinese made tools; frankly, I think there is some cultural differences, and they do not embrace the meaning of the word "quality" in the same way.  Regardless, I did just buy that 1052E.

Chinese companies can produce top quality products, it's just that 90% of the market  seems to be the junk stuff built to the lowest price using what parts they can get this week from the markets.

And likewise, western companies can get their products made in China to a high standard, but you have to drive them hard and control everything.

Dave.

[MikeO]

And therein lies the great value of your reviews and teardowns, Dave.

Perhaps there is a bit more opportunity as well?  Maybe you would consider adding some polls to the site, say a post one year and two year ownership with a few basic questions, like still working?  Still accurate?  Good service/support/repair/repairability?  Maybe you already do, and I've failed to peruse the site before making such recommendations--can you tell I was moved to management?

Speaking of which, is there anything easier than volunteering someone else for work?  I think back to countless meetings with management, and getting the question, "Can't we just..."

No!  WE can't, cause you can't do anything!  I can, but you'll fail to give me the budget and resources, and if I argue for them, you'll argue back, as if this were a negotiation, and not statement of fact.  Of course, those were just the words in my head.  And how would it go from there?  The mechanical engineer would check out, the power supply engineer would turn down his hearing aid, the other controls engineer would get excited, knowing that it would fall to me, meaning I'd miss my other goals, making him look more productive...goodness gracious, I do not miss being an engineer in a dysfunctional company.  Self-employment can be tough, but I'll take it!

And therein, I suppose, is why a forum like this is so refreshing to me--it reminds me of the good side of my time as a designer: the culture of our lab.  I miss the day-to-day working with my colleagues, the other engineers and techs, their mutual respect for each others unique skills, experience and education, and the willingness to offer help to one another whenever it was requested.  Nice job fostering and maintaining that culture in your forum Dave.

Cheers all, it's back to work for me.

Regards,
Mike O'

[saturation]

An e-load was in my sights for some time too.  Welcome MikeO, some comments.

I concur with Dave, China can make good consumer or low end general purpose technical stuff, the reviews by Dave and others prove it.  China can send a man into space they can certainly make a decent GP electronic load  .    The trick is finding who and what, and that's where the reviews come in.


On Array:  FWIW the founders of Array are Taiwanese engineers, not PRC, so they have a much more advanced design ethic, it probably explains why the build quality is more consistent with say Instek than Atten.  The factory is in PRC.  Array is very likely OEM for many look-alikes,  such as Tekpower, IWH or CSI.  I can say this because their product manuals, software, and photos of the devices [ 3710 and 3711 at least] are identical to Array's model, except for the brand name.  I haven't had time to tear mine down and confirm that by looking at the PCBs.



The forum has a lot of reports, but few are collated or polled.  Any member can make a query and ask. 

One thing about PRC devices, the bolded item in your quote below, is in most instances you should expect low to none.  A key feature of reviews I look for is to estimate its DIY repair-ability, which is why a tear down is most helpful.  Its another reason I look at the PRC devices because they are often made with older technology, or more generic parts, and the probability of repair is higher.

The Kikusui PLZ is a superior device in many ways, but the great unknown is how it was used.  Power devices are likely to wear out with heavy use to its rated power, so its a bigger risk.  I think a repair cost may outstrip its eBay cost given Kikusui bottom line models start over $3000.  No schematic and only 12 years old or so for PLZ300W, could be challenge to self service.
 

And therein lies the great value of your reviews and teardowns, Dave.

Perhaps there is a bit more opportunity as well?  Maybe you would consider adding some polls to the site, say a post one year and two year ownership with a few basic questions, like still working?  Still accurate?  Good service/support/repair/repairability?  Maybe you already do, and I've failed to peruse the site before making such recommendations--can you tell I was moved to management?

[olsenn]

Chinese companies can produce top quality products, it's just that 90% of the market  seems to be the junk stuff built to the lowest price using what parts they can get this week from the markets.

And likewise, western companies can get their products made in China to a high standard, but you have to drive them hard and control everything.

Outside of China, you can have a very high quality product made for a very high cost, or a high quality product made for a high cost. In China, you can have a very high quality product made for a very high cost, a high quality product made for a high cost, or a low quality product made for a low cost. If people outside of China want to make a very high or a high quality product, they'll just do it in their own country.

[T4P]

Chinese companies can produce top quality products, it's just that 90% of the market  seems to be the junk stuff built to the lowest price using what parts they can get this week from the markets.

And likewise, western companies can get their products made in China to a high standard, but you have to drive them hard and control everything.

Outside of China, you can have a very high quality product made for a very high cost, or a high quality product made for a high cost. In China, you can have a very high quality product made for a very high cost, a high quality product made for a high cost, or a low quality product made for a low cost. If people outside of China want to make a very high or a high quality product, they'll just do it in their own country.

I don't agree. Look at rigol!

[MikeO]

All interesting points.

Certainly, I won't pretend buying old gear, of unknown provenance, from unknown sellers, is anything but high risk.  It's a bit like buying a used car.  The pics of the gear matter, the wear on the knobs, et cetera, just like the wear on the accelerator and brake pedals are more believable than the odometer.  When I buy used gear, it is with the assumption that it may have been an error, only time will tell.  And certainly, I wouldn't want to fail to reiterate what Saturation said, how it was used (duty cycle, and what percentage of maximum load) I cannot detect from a photo.  It's a gambler's game, on the average, will I save enough to justify the risk, adjusted for the fact that I can get some better gear than what I'd buy new?  And then there is the type of risk, as bad gear doesn't just cost money, it costs time, and they have different values in a home lab than a commercial one.  In buying that load, my assumption is that if it fails, and I can't troubleshoot and repair it quickly, I'll be giving it away, as the repair cost will be higher than replacement.

My experience with PRC manufacturing is out of date.  But, I'll share some lessons...  It is getting almost impossible to compete, over some volume, if you aren't doing some manufacturing in the PRC.  In order to succeed with manufacturing in the PRC, you've got to maintain very high quality assurance, and quality control is generally best done outside of the PRC.  Some quality assurance can be accomplished by supplying the components, but that often fails, as the components you supply are often resold, and cheaper parts substituted.  It has been suggested to me that the lack of financing available in the PRC makes this a necessary model to achieve required plant improvements.  Further, in the PRC, the concept of intellectual property is very, very different.  I wonder, is that an effect of communism?  A concept of collective ownership?  We found that whenever you manufacture in the PRC, you will see your product elsewhere on the market, unlicensed, carrying someone else's name.  Further, you've no legal remedy, other than if it's patented, you can get it seized at the importing country's customs, at great expense.  Some would suggest, why pay for a brand name?  To me, because I see a value in the quality control, and after purchase support.  And because I believe in a name, that someone has pride in it, and is loathe to allow others to spend up that good will in the name of short term profits.  Certainly, it's no guarantee.  Goodness knows, I'm still using every Milwaukee power tool I've ever bought, except one, when it was an American company, and I burn up two a year on all the units since they've become an Asian company.  All my Fluke meters are made in China, and they've seen some unbelievable abuse, so they are succeeding in manufacturing in the PRC.

I think that brings us full circle.  We need to depend on our colleagues, and forums and reviews like those found here on eevblog, to share their experiences, and to do what those of our ilk tend to do: take things apart.  As such, I'm fortunate to have found you all.

If not for this site, I'd not have purchased the Rigol 1052E.  I'd probably have some chitty-chitty-bang-bang old scope with dried out caps exploding when I fired it up, and a burned screen, frustrated, and cursing my frugality.

I think the one point I intended to make, and failed to, aimed more at the beginners, is that you'll never have the budget to get all you want and think you need.  But, you sure will need some gear to earn enough to get close.  Don't be afraid to buy some old gear and basic gear that is inexpensive.  I think few would argue, the only thing that comes close to the value of a bench supply is a second bench supply, the only thing that approaches the value of a scope is a second scope (preferably analog if your #1 unit is digital).

When I chose the Kikusui, it was because I didn't want to spend on a new Array unit, as that would cut my budget for a function generator; I had spent so much time researching my scope purchase, I didn't have the time to research my load purchase; so, I went with a unit which I had enjoyed a long and positive experience.  Also, I was compartmentalizing my risk.  If my scope fails, my project will be in big, big trouble.  If my load fails, I'll get by with lightbulbs and resistors.  I can think of many a project where the opposite would be true, and I'd survive the lack of a scope, but I'd need an accurate, predictable, consistent and bulletproof load.  All in all, the win will be if, at the end of the job, beyond the profit, I've increased my equipment, and am that much more capable of taking on the next project, not needing to purchase that much more.

Thanks for the dialogue.  It's quite informative and clarifying.

Regards,
Mike O'

[T4P]

Well so i saw some Vantek CA5030 loads going for 285USD w/o shipping on precisegauge and i googled it ...
I didn't expect a local's (arguably most biased reviewers on earth) tech website to get a little serious but they actually use USB meters to monitor voltage WTF
But still they bet some money on the CA5030 http://www.istorya.net/forums/computer-hardware/521871-behind-scenes-vr-zones-psu-testing-station-mark-ii.html#post12959202

[ElektroQuark]

Ah!

[saturation]

Very well said, MikeO. Your comments are more a study of PRC manufacturing issues using our electronic loads as a case study, I hope others take the time to read it.  I agree 100% with your comments.

I'm not sure if you still have manufacturing ties in PRC, but sadly, all issues you lament are still ongoing as of 2012.  Not to take this thread off topic,  there are discussions on other threads here about it.

All interesting points.

Certainly, I won't pretend buying old gear, of unknown provenance, from unknown sellers, is anything but high risk.  It's a bit like buying a used car.  ..
My experience with PRC manufacturing is out of date.  But, I'll share some lessons...  It is getting almost impossible to compete, over some volume, if you aren't doing some manufacturing in the PRC.  In order to succeed with manufacturing in the PRC, you've got to maintain very high quality assurance, ....

[saturation]

Nice! Ed, I'm sure Gossen did their homework of this unit before putting their name on it.  They haven't remove all traces of Array's name on it.  I downloaded the manuals and they are clearly Array's manuals.  The software is identical.  Lastly, they didn't remove Array's name from the software's splash screen.

http://www.gossenmetrawatt.com/gmc/english/produkte/eloadms.htm#

Ah!

[saturation]

Nice, that speaks well for Vantek, assuming the setup holds up to repeated use.  Since the original article was published 7/12, time will tell if the units are as reliable as the Array.  What they did looks surprisingly similar to what techpowerup's crmaris did in Greece back 2011 using Array loads instead.  The only reviews VRZone has using this setup began in July 2012, so usage has not much history yet.

There are many budget basic e-loads from China not available in the US: Beich as briefly reviewed below, Vantek, MH, ... here's a one stop list of several models:

http://www.goodluckbuy.com/index.php?target=products&mode=search&subcats=Y&type=extended&avail=Y&pshort=Y&pfull=Y&pname=Y&pkeywords=Y&cid=0&q=electronic+load&x=0&y=0

Am not sure what to make of it as a bang for buck.  On the low end the price/performance is very similar to the 3710.  Add S&H cost, they come out ~ $350 delivered, same price as direct from a US vendor.

Itech/Maynuo/BK Precision versions [ not sure who the original is] however, are a class above the others.

Well so i saw some Vantek CA5030 loads going for 285USD w/o shipping on precisegauge and i googled it ...
I didn't expect a local's (arguably most biased reviewers on earth) tech website to get a little serious but they actually use USB meters to monitor voltage WTF
But still they bet some money on the CA5030 http://www.istorya.net/forums/computer-hardware/521871-behind-scenes-vr-zones-psu-testing-station-mark-ii.html#post12959202

[T4P]

It's not only them
There's tonghui, atten, Crown (Well ... Atten rebadge), ITECH ( the most expensive one out of all but you can only find them in china well of course ... BK's not going to let ITECH sell outside ) And REK

[saturation]

Thanks.  I briefly looked at them, but couldn't find Crown.  Tonghui appears to be a Beich, Atten does both rebadges, and REK is an Itech, all for about the same price.  It would be best to buy it from the OEM, if possible, since they would know their product best. 

Sample links:

http://en.ebuy17.com/product/4065/
http://trade.e-to-china.com/company-cCB3BA/Changzhou_Tonghui_Electronic-pBAB1G1/CH8711_Program_DC_Electroic_Load.html
http://www.attenelectronics.com/Products/Power_Supply/DC_Electronic_Load/

It's not only them
There's tonghui, atten, Crown (Well ... Atten rebadge), ITECH ( the most expensive one out of all but you can only find them in china well of course ... BK's not going to let ITECH sell outside ) And REK

[T4P]

You can find them all over at taobao.

[saturation]

There are several threads discussing China branded e-loads so I'll summarize points.  Rufus suggests the brands mentioned have much similarity, one thread suggests the BK/Itech/Maynuo/ older Array model are designed by the same person, but I think others are distant copies, some changes don't look optimally thought out, but they seem cheaper to implement.  So for example, the Beich lacks a quality ethos you see in common with BK, Itech, Maynuo or Array.

Here's a comparison of Rufus' Beich CH8710B photo, a clearer photo of an Array [both rated at 150W], and a screen grab from Dave's BK 8500 review [300W].  Sorry its big, but the details are needed to contrast the 3.

The most obvious on the PCBs are thermal management strategies.  The BK and Array use 2 sets of forced cooling heatsinks, while the Beich, rated for the same wattage as the Array, uses one.  It may not be a problem if the fan cfm is >=2x a single Array set, but clearly the Beich case is missing one set of fan/sinks.

Since all 3 claim to have thermal overload protection, if the fans can't handle the load I presume the load with be cut off until they cool down, so if the Beich's copied those features it has a backup plan since it relies on a single fan for all its cooling. 

On both the Array and BK units, the low-ohm power resistors [ the twisted coils of wire in the BK] and heat sinked TO220 device are within the airflow stream of the fans.  There are cutout vents on the side of the BK for intakes, as well as a ventilated bottom chassis.  On the Array, the vents are on the bottom of the PCB both as powered intake fans and passive holes.

On the Beich, while the bottom seems quite 'open' to ambient, the fan is on the opposite side of the input resistors [ the yellow A in the photo], and resistors on the load board marked C, are on top of the PCB, these resistors will have to rely on indirect airflow for cooling.   Beich could have put the single load module on the right side to help cool down those resistors.  On the Array, similar functioning resistors on the load board marked a,b are on the bottom of the PCB, are not visible because they are in the airflow stream of the fans.

In thermal management, overdesign is best, because heat dissipation will suffer drastically if ambient temperature is higher [ such as in hot climates] or obstructions to vents [ such as placing the unit against a wall]. 


Safety

Since few are UL, ETL, TUV etc.,  certified one has to rely on the CE mark or doing one's own due diligence to determine what limitations to put on these eloads.

Both the BK and Beich have line voltage switched on the PCB; the Array uses a separate switch and only low voltage appear on the PCB.  Not big issues, but its safer to keep line voltage separate from low voltage lines in case high voltage transients in mains voltage enters the unit.

Both Array and BK add MOVs as surge input protection, and the binding posts, which potentially can contain higher voltages, are kept free of other lines as potential arc points, the only wire nearest it is a ground wire quite some distance away.   The Beich seems to only have high voltage capacitors on the input, and there are a bunch ribbon cable crossing near its binding posts; one could move them away a bit as an arc may not be lethal to the operator but more lethal to the control electronics.

Modern high voltage design prefers cutout to control line clearances on PCBs.  Eyeballing, the creepage distances on the Array and Beich are acceptable but adding cutouts would be better.

The Array has surprising design elements that provide safety in redundancy but at greater cost.

For example, Array has two thermal sensors for each load cell, 2 fans for each cell.  I'm not sure but suspect each fan is controlled by each cell.
 
The Array design takes trouble to add separate ground wires to the chassis walls, and terminate them to the same ground point.  This insures that the ground lines have lowest impedance path, rather than bolting it to the chassis.

I'm intrigued by the x6 MOSFETs at the input.  I'm not sure how its configured as a switch, but it gives a banked series rating of 330V at 110A.  I'm guessing its either a high voltage reverse input protection but how it does it I'm still examining, and will report back.  A similar configuration is not present on the BK or Beich.

So in conclusion, even if Beich units copy another's design there is a big difference in implementation, considering the list price is often similar to Arrays. 

The Array seems very competent in hardware for what its designed to do, and for small labs, its use of through hole, and fairly generic parts makes its easier to service DIY.  More later as I finished a detailed review and performance and finally safety test.

[robrenz]

Wow saturation    so much for BK just being a rebrand. Thanks for the pictorial comparison.

[saturation]

I'm fairly intrigued by these e-loads, it has the look of being done by a very small team, even one man [ kmel in another thread suggests the designer Xiao Tony was formerly at Array, and the 3710a looks like an early version of models later of Itech/BK/Maynuo.]

However, for bang for buck, the Array is looking like a very decent box if you don't need to test systems using constant voltage, and can deal with its buggy software.

T4P provided some links to vendors in China per se, via taobao.com.  Units from Beich, Maynuo and Array for the same wattage are priced near the same, even if Array is an older design.  I think its main feature is its likely built like a tank and can take abuse, and Array is the only model you can get in the USA directly as OEM for other brands, like TekPower. 

Wow saturation    so much for BK just being a rebrand. Thanks for the pictorial comparison.

[saturation]

I've just posted a hardware teardown of the Array 3710a dc electronic load.  My model is rebadged as Tekpower.

http://www.flickr.com/photos/igsaturation/sets/72157631565608376/

There are 31 photos so the above link is faster.  It would be best to comment on this thread so the discussion has a larger audience than the Flickr site.  I'll steer any comments on Flickr back here or mirror replies.

Since I have confidence the unit is built well, its now undergoing stress testing and I'll post a functional review later on this thread.

 

[free_electron]

ah , good. i just bought a 'out-of-spec' 3711 for cheap on fleabay. so i can compare.

[saturation]

Nice, and congratulations.  I'd be interested in your comments, free_e-.  I was wondering what happened to this unit.

http://www.ebay.com/itm/TekPower-3711A-TP3711A-Programmable-DC-Electronic-Load-0-360V-300W-/290771559411?pt=LH_DefaultDomain_0&ssPageName=RSS:B:SHOP:US:101&hash=item43b355e3f3&nma=true&si=4%2FoYUNwtxMPRuUXZmUBrIJTg4og%3D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

If its you, its in good hands.

I wonder if the 150W, which is really 200W, is just crippled in firmware and is in hardware a 300W.  Much of its components suggest it is.  A photo of your PCB and your comparison would clear it up easily, when you've time to get to it. 

ah , good. i just bought a 'out-of-spec' 3711 for cheap on fleabay. so i can compare.

[LaurenceW]

Greetings all,

I've just posted a rather wordy initial impression of my Maynuo electronic load, here

https://www.eevblog.com/forum/product-reviews-photos-and-discussion/why-is-bk-precision-still-in-business-bk8500-programmable-load-oem-found/30/

I'll get the lid off this weekend, and grab some pictures.

[saturation]

Excellent review, must read for anyone considering an eload.  Please keep it up, and as many pictures as you can!  I'll post comments on that thread rather than here.

Greetings all,

I've just posted a rather wordy initial impression of my Maynuo electronic load, here

https://www.eevblog.com/forum/product-reviews-photos-and-discussion/why-is-bk-precision-still-in-business-bk8500-programmable-load-oem-found/30/

I'll get the lid off this weekend, and grab some pictures.

[free_electron]

Yep. Me. Snatched it for less than that

I have some 'reverse engineering ' info.
The meanders on the pcb are there for a purpose. The two powerfets at the back have their own 0.1 ohm sense resistor to close the loop. These two resistors share a single trace on the board that is via-stitched between top and bottom layer and comes to the front of the board. The meanders on the front resistors inject the same trace length to the star point. The reason is load balancing. The pcb trace resistance would be different between front and back and the front fets woul pull more current than the back. Deliberate operation. Good design.

The bank of 6 mosfets on the main board is for range switching.
The use either 0.2 ohms for current measuring , in series with 0.02 ohms ( five 0.1 in parallel ). At high current they turn on the bank of six mosfets to short the 0.2 ohms out.

A relay toggles between the sense points. ( strange.. No analog mux ... Probably because there is a post divider protecting against large voltages.. )

My machine is off in the voltage measuring department. The programmed and measured currents are correct. The voltage measured on the terminals is wrong , so it probably needs adjustment.

The sticker said. Cannot adjust , but they didnt even try.... None of the pot seals are broken and this machine has no electronic calibration.... Lazy callabs...