Author Topic: "Array" electronic loads - any opinions?  (Read 2190 times)

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Offline Lomax

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"Array" electronic loads - any opinions?
« on: December 01, 2018, 07:51:07 pm »
There's not a lot that I miss in my lab, but one gaping hole I've been aware of for some time is the lack of an electronic load. I've now got a marine battery charger I'm trying to repair, as well as three Exide "blue top" flooded lead acid batteries I'd like to test, which makes me think it might be time to plug that hole. While I'd normally hunt for second-hand gear from a reputable manufacturer I'm surprised by how expensive even tatty second-hand electronic loads are. I have picked up older top of the range scope, bench meter, function generator, power supply without ever paying >£300 for anything, but when it comes to electronic loads, despite looking for weeks, I've found nothing remotely interesting <£1k. This is way outside what I'd be prepared to pay, so I've resorted to looking at new Chinese units >shudder<. Purely based on visual appearance and specs, the Array 3720A, 3721A, 3722A or 3723A look quite interesting, but I'm having trouble finding any reviews of them. Anyone here have any opinions on these units? The Array 3720A (250W 80V) can be had from Labtronix @ £419.


 

Offline nctnico

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Re: "Array" electronic loads - any opinions?
« Reply #1 on: December 01, 2018, 07:55:45 pm »
The Array loads are nothing special but they do the job and it seems the one you found is a newer iteration of the existing series. Many low end brands sell loads built using the same recipe.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline 001

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Re: "Array" electronic loads - any opinions?
« Reply #2 on: December 01, 2018, 07:56:40 pm »
There's not a lot that I miss in my lab, but one gaping hole I've been aware of for some time is the lack of an electronic load. I've now got a marine battery charger I'm trying to repair, as well as three Exide "blue top" flooded lead acid batteries I'd like to test[/url].

Wrong way
You can`t check CHARGER with constant current load -- it is simply two current regulator in series  :-//
 

Offline nctnico

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Re: "Array" electronic loads - any opinions?
« Reply #3 on: December 01, 2018, 07:58:48 pm »
There's not a lot that I miss in my lab, but one gaping hole I've been aware of for some time is the lack of an electronic load. I've now got a marine battery charger I'm trying to repair, as well as three Exide "blue top" flooded lead acid batteries I'd like to test[/url].
Wrong way
You can`t check CHARGER with constant current load -- it is simply two current regulator in series  :-//
In that case you set the load to constant resistance or constant voltage. But yes, the cheaper loads may have control loop issues.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Offline Lomax

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Re: "Array" electronic loads - any opinions?
« Reply #4 on: December 01, 2018, 08:06:51 pm »
Wrong way
You can`t check CHARGER with constant current load -- it is simply two current regulator in series  :-//

Who said anything about CI? Electronic loads have other modes, and hooked up to a PC they can simulate a lot of things - including batteries.

Prodigit Application Note 304 - Testing of battery chargers and batteries
 

Offline 001

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Re: "Array" electronic loads - any opinions?
« Reply #5 on: December 01, 2018, 08:10:34 pm »
Wrong way
You can`t check CHARGER with constant current load -- it is simply two current regulator in series  :-//

Who said anything about CI? Electronic loads have other modes, and hooked up to a PC they can simulate a lot of things - including batteries.
 

WOW
Is so expensive gear really needed to fix charger?
 

Offline ci11

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Re: "Array" electronic loads - any opinions?
« Reply #6 on: December 01, 2018, 08:49:29 pm »
I heard some Array eLoad models do not feature thermostatically controlled fans, which means they can be noisy. You may want to confirm this with the specific model you are looking at - it stopped me dead in my tracks on a 3723A.
 
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Offline Jester

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Re: "Array" electronic loads - any opinions?
« Reply #7 on: December 01, 2018, 10:12:52 pm »
I can't comment on that exact model, however I did have an earlier version and found that changing settings was a very unintuitive multi-step PITA, hopefully they have fixed that. It was such a PITA I sold it, much preferred my old Kikusui and B&K for simple load testing.
 

Offline Lomax

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Re: "Array" electronic loads - any opinions?
« Reply #8 on: December 03, 2018, 09:07:27 am »
Thanks everyone! I've done a lot of reading here and elsewhere, and I'm really none the wiser. Super confusing with all the rebranding and copying that's going on and it's pretty much impossible to make an informed choice between Maynuo, ITech, BK Precision, Array, Atten, Beich - or indeed Gossen (who seem happy to put their name on the Array units, at twice the price). FWIW I do like the physical design (case, display, controls) of the Array 372x series, and the specs seem fine, but the fans being "always on" is a minus. Cannot decide :(
 

Offline Kean

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Re: "Array" electronic loads - any opinions?
« Reply #9 on: December 03, 2018, 09:42:44 am »
I believe the BK Precision models are rebrands of the ITech DC Loads.  I have the ITech IT8511+ and an older IT8511.  I'm pretty happy with them, and I believe I paid about AU$500 each for them delivered to Australia.  The IT8500 series is meant to be "cost effective" and it has been around for a while, both of which are good and bad.

Manuals available on-line (as well as reviews) so you can check if it suits your needs.
http://www.itech.sh/en/product/DC_electronic_load/IT8500+.htm

I connect for PC control and logging via the isolated USB to TTL serial adapter (IT-E122).  The PV9500 application to control them isn't that great, but they do support SCPI if you want to do something fancy.  One thing annoying compared to the array is that the sense terminals are on the rear of the unit.

I've more recently also bought the ITECH IT7321 programmable AC PSU and it is pretty nice, and has inbuilt USB & ethernet like some of their more expensive DC load models.
 

Online HKJ

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Re: "Array" electronic loads - any opinions?
« Reply #10 on: December 03, 2018, 10:02:19 am »
I connect for PC control and logging via the isolated USB to TTL serial adapter (IT-E122).  The PV9500 application to control them isn't that great, but they do support SCPI if you want to do something fancy.  One thing annoying compared to the array is that the sense terminals are on the rear of the unit.

I have never seen SCPI on my ITECH loads.
They are easy enough to control and log from a computer with their binary protocol and I use that a lot.
 

Offline Kean

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Re: "Array" electronic loads - any opinions?
« Reply #11 on: December 03, 2018, 10:36:07 am »
There are manuals on the website for both the binary "frame" protocol and SCPI programming
http://www.itech.sh/en/support/Down-27.htm?model=it8500
 

Offline MarkL

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Re: "Array" electronic loads - any opinions?
« Reply #12 on: December 03, 2018, 02:25:17 pm »
I have two of the Array 3723A loads, both with the optional GPIB interface.  One is about 5 years old and I liked it enough to buy a second one earlier this year for some dual-rail supply testing.

The 372x series does not appear to be based on those tired designs that get copied between BK, Maynuo, and ITech.  I've only seen Gossen reselling it, as you mentioned.

The fans are thermostatically controlled, but they are not "whisper quiet" when the unit is turned on and they get louder from there as it dissipates any significant load.

The GPIB and RS232 (and optional USB which I don't have) all support SCPI which I've used quite a bit.  I haven't found any bugs, which I can't say about other loads I've tested in the past (BK, Aim-TTi).  All the interfaces are isolated (no isolator/level translator dongles like some of the BK units).

I've found it easy to setup and use.  The menus are simple and logically arranged.  The loop response is excellent and I've never had it oscillate (although given enough time I could probably find some conditions that annoy it).  I really like that all the connections, besides computer control, are accessible on the *front* (duh).

Both of my units have been performing well with one minor exception.  The older one seems to have developed an intermittent issue over the last year or two with, I think, the remote voltage sense relay inside the unit.  The display was showing close to 0V when there was quite clearly more than that.  Cycling the relay by temporarily disconnecting the remote sense terminals cleared the problem.  It's only happened a few times, so I haven't been able to track it down definitively.

I've posted a bunch of times about this load if you search for "site:eevblog.com array 3723a".  Internal construction is solid, commensurate with the price in my opinion.  There's some internal photos here:

  https://www.eevblog.com/forum/testgear/any-experience-with-scpi-and-chinese-dcprogrammable-loads/msg352717/#msg352717
 
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Offline ArthurDent

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Re: "Array" electronic loads - any opinions?
« Reply #13 on: December 03, 2018, 03:49:03 pm »
After spending years of digging big resistors I could use as loads for testing power supplies out of my junk pile and never finding quite the right size and value, I broke down and bought a good electronic load. I searched around and finally bought a used Array branded 3711A  0-360V/0-30A/0-300W unit that looked just like new for under ½ the new price. The newer 3720A series seem more versatile than the 3711A but I was amazed at how expensive some new Eloads are. There are also some inexpensive Eloads on eBay that are around $150 from Chinese sellers but I wanted an Eload that I knew would last and be trouble free and these lower end ones made me leery. 

Everything in life is a compromise but this Array 3711A Eload I bought seems to do everything I want it to do. It is very small for what it does and I bought the USB interface for it as well. The control software seems like an afterthought but it will allow me to generate a graph of battery discharge curves without much difficulty.  Any piece of equipment you buy has a learning curve to understand the controls and once I got used to the 3711A it isn’t that difficult to set it up for the testing I want to do. I also found the readouts to be quite accurate.

The fans are thermostatically controlled with 2 fans on the back and 2 fans on the bottom. When you are dissipating about 300 watts and all the fans turn on it can be a little loud but that’s to be expected. Here is a photo of a Astron RS-20A 20A power supply connected to the Eload drawing 20A and a photo of the fans.
« Last Edit: December 03, 2018, 03:51:43 pm by ArthurDent »
 
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Offline Lomax

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Re: "Array" electronic loads - any opinions?
« Reply #14 on: December 03, 2018, 04:43:13 pm »
The fans are thermostatically controlled, but they are not "whisper quiet" when the unit is turned on and they get louder from there as it dissipates any significant load.

Great to hear; I was scratching my head as to why they would have removed this, as suggested by some other posts. I can live with always on fans, but not if they're running at full blast the whole time.

The GPIB and RS232 (and optional USB which I don't have) all support SCPI which I've used quite a bit.

The serial port is essential to me. Gossen publish the SCPI command set here: https://www.gossenmetrawatt.com/resources/la/spl/spl-scpi-programming-sb_gb.pdf

The loop response is excellent and I've never had it oscillate

Ever tried it with a PWM power source?

I really like that all the connections, besides computer control, are accessible on the *front* (duh).

Agreed.

There's some internal photos here

Yep, saw those. Looks v. nice!

The newer 3720A series seem more versatile than the 3711A

The newer units have a CV mode for one thing, and the physical appearance is more professional. But the "affordable" 372x loads only handle up to 80V, and even the pricier models only go to 200V, while the older 371x go to 360V - that said, I would be interested to hear some use cases where you need to handle higher voltages; can't seem to think of any situation where I'd deal with DC > 80V?

I was amazed at how expensive some new Eloads are.

Indeed. Electronic loads appear to be quite a bit more expensive - relative to complexity - than other T&M gear, for some reason.
 

Offline MarkL

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Re: "Array" electronic loads - any opinions?
« Reply #15 on: December 03, 2018, 05:03:52 pm »
The loop response is excellent and I've never had it oscillate

Ever tried it with a PWM power source?
Not on a regular basis, but I did do a little bit of testing here:

  https://www.eevblog.com/forum/testgear/array-electronic-loads/msg756507/#msg756507

What are your requirements?
 
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Offline Lomax

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Re: "Array" electronic loads - any opinions?
« Reply #16 on: December 03, 2018, 07:23:23 pm »
What are your requirements?

To buy precisely one electronic load which has a good chance of being usable for whatever I might need one for in the future.
 

Offline nctnico

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Re: "Array" electronic loads - any opinions?
« Reply #17 on: December 03, 2018, 09:58:18 pm »
What are your requirements?
To buy precisely one electronic load which has a good chance of being usable for whatever I might need one for in the future.
:-DD It ain't gonna happen. You either get TEA, GAS or a project which requires you to buy yet another load. For example I've got 5 DC loads myself (2 Array 3710A, an Agilent N3301 with two different 500W modules, a self built one and a TDI Dynaload 100-100-1500. I use the Array 3710A the most for general purpose testing because they are quiet and small/light enough to move without much hassle.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Lomax

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Re: "Array" electronic loads - any opinions?
« Reply #18 on: December 04, 2018, 08:25:18 am »
Quote from: Me
I'm thinking of buying an electronic load

Quote from: Forum User
Bah, what do you need one of those for, just use a resistor!

Quote from: Other Forum User
LOL, you think you can manage with just one electronic load?

Quote from: Me
...
 


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