Author Topic: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown  (Read 13940 times)

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Offline EEVblog

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EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« on: September 18, 2017, 08:50:07 am »
Dave teards down the new Rigol DL3021 Electronic load and has a play around with it.

http://emona.com.au/products/electronic-test-measure/electronic-loads/dl-3021.html#.Wb7yY7Kg9hE





 

Offline paulcav

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #1 on: September 18, 2017, 09:22:43 am »
"teards" that's a new word? :)
 

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #2 on: September 18, 2017, 09:46:30 am »
If Rigol ever want to be taken seriously as a major T&M company they're going to have to do better than this. OK loads are a relatively niche product, but bad design ( graphic or otherwise) reflects across the whole product range.

The voltage regulator thing is just ridiculous - even they can't design a sufficiently quiet switching reg, they've got a sodding great heatsink in there they could have used. 

The graphic design aspect reminded me of the laughably awful Neoden video - seems like the Chinese would rather do a bad job themselves than hire someone that knows what they are doing. 
 
I really can't see any Chinese company reaching the same level of brand reputation as the likes of  Keysight, Tek, Keithley, R&S etc. 
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Offline theorbtwo

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #3 on: September 18, 2017, 10:07:17 am »
Thought this might be an interesting watch, considering that I've been having lots of fun reverse engineering a ds1054z lately.
https://youtu.be/Tk_3rYKWIIg?t=826 looks a lot to me like that is the main CPU of the whole thing -- that's a freescale MC i.MX, the same series of processor that powers the ds1054z.  Hopefully a rather newer one ... nope.  it's the i.MX283, very very similar to the i.MX286 that powers the ds1054z scope.  Freescale considers that a legacy processor, so I'm rather surprised they went with something so old.
  There's also both RAM and flash on there.  Nicely, they've given us a couple of nicely marked 0.1: unpopulated connectors on the top -- ARM-JTAG and BOOT.
I also wonder a bit if that's a real PCI card.  It's not out of the realm of possibility, and it'd be somewhat handy during product development.
Also, note that it's called DigitalBoard in the silkscreen, not IO, or peripherial, or back-panel or the like.

(And there's the same 5-pin diagonal FPGA JTAG connector.)

... yeah, he's coming to the same conclusions as I did, just a bit slower.

Anyway, the design is very similar to the scope, in terms of what chips they are using.  The difference is that they've moved to more boards, which means they can mix and match better and hopefully put out products quicker.  I am still surprised they've gone with such an old CPU, though.
 

Online wilfred

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #4 on: September 18, 2017, 11:26:38 am »
I really can't see any Chinese company reaching the same level of brand reputation as the likes of  Keysight, Tek, Keithley, R&S etc.

Why? What's unique about China that prevents this from ever happening? People said the same about Japanese cars and Korean cars at one time. Surely all it takes is for the market niche they choose to fill opening up to include the premium end. They will probably drift towards this end when they themselves become undercut at the low end. Much like Bangladesh does to them in textiles.

It won't happen in the next few years but come back in 20 years and see if you think the same. If there is any country that can take the long term perspective it has to be China. 
 
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Offline technogeeky

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #5 on: September 18, 2017, 03:07:26 pm »
Someone beat me to it on YouTube comments, but I'm pretty sure that the problem with the wheel is essentially a PEBKAC. The green underline is selecting which decimal place is currently wheel controlled. Presumably some action (pressing the wheel in?) will cause the selected decimal place to shift (to the left, since the rightmost one is currently selected around 22 minutes in).

If you select the tenths or ones place, perhaps it could actually have velocity or acceleration or whatever and you might have missed it.

 

Offline Rbastler

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #6 on: September 18, 2017, 06:05:49 pm »
Damn, and I really wanted one, like a lot. Now not so much....
The reversed italics and the various fonts are horrible. I agree the main binding posts suck, but I do like the sense posts.
I really would like to use something else than CC on the battery mode...and switching the output of when going into store/utility... meh. And again the linear regulators...Then the presumably failed calibration ?
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Offline Brumby

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #7 on: September 18, 2017, 06:28:32 pm »
Watching that - and the video Dave mentioned for a DIY solution, I'm half thinking of building my own - with a microprocessor driving it.

Time to brush up on power mosfets....
 

Offline Worsdier

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #8 on: September 18, 2017, 06:47:41 pm »
I'll still consider buying one if they add CP mode to the battery program. They did inform me that the feature will be added to a firmware update at the end of August, but that date came and went and I don't see a firmware update published anywhere yet.
 

Offline Rbastler

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #9 on: September 18, 2017, 06:54:02 pm »
I'll still consider buying one if they add CP mode to the battery program. They did inform me that the feature will be added to a firmware update at the end of August, but that date came and went and I don't see a firmware update published anywhere yet.

Same here.
I still trust Rigol more, than one of those copied no name electronic loads.
I really hope, the fix the issues they can in firmware or offer maybe later a free hardware upgrade.
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Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #10 on: September 18, 2017, 07:18:48 pm »
Shunt: http://www.isabellenhuette.de/fileadmin/content/praezisions-leistungswiderstaende/BVS.PDF
Isabellenhütte BVS, 50PPM/K. It is a cheap shunt.

I'm starting to think, that they laser the opamps for other reasons than IP. Maybe they dont have the rights to import them to china. I mean, designing an amplifier for low side current sensing? Really, that is an IP worth protecting?
 
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Online mikeselectricstuff

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #11 on: September 18, 2017, 07:26:47 pm »
I really can't see any Chinese company reaching the same level of brand reputation as the likes of  Keysight, Tek, Keithley, R&S etc.

Why? What's unique about China that prevents this from ever happening?

The culture. The rigid educational system that doesn't put any value on imagination or creativity, so there is no significant innovation, just cost-engineering of Western products.
Rigol are generally regarded as the best of the Chinese T&M suppliers yet they're still turning out products with poor software design, and rubbing numbers off chips.
How many Chinese companies can you think of that are leaders in their field? The only one I can think of is DJI.
And in a "professional" rather than "consumer" field?  Lenovo maybe, but they inherited a lot from IBM.


 
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Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #12 on: September 18, 2017, 07:49:50 pm »
I really can't see any Chinese company reaching the same level of brand reputation as the likes of  Keysight, Tek, Keithley, R&S etc.

Why? What's unique about China that prevents this from ever happening?

The culture. The rigid educational system that doesn't put any value on imagination or creativity, so there is no significant innovation, just cost-engineering of Western products.
Rigol are generally regarded as the best of the Chinese T&M suppliers yet they're still turning out products with poor software design, and rubbing numbers off chips.
How many Chinese companies can you think of that are leaders in their field? The only one I can think of is DJI.
And in a "professional" rather than "consumer" field?  Lenovo maybe, but they inherited a lot from IBM.
Well, there is also Xiaomi, with the Yi product line. But something else will happen. Chinese copy something, they sell more. Make more profit with the copy than the original design company. And then buy them. It happened for Segway. We all know the story.
It happened to Riot Games, they made a software for 67 million players a month. The copy Chinese software is used by 200 million. Copy software company buys riot games.
Soon they dont need to copy, because they have the IP, and they pay the western engineer to do the work.
 

Offline 2N3055

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #13 on: September 18, 2017, 07:57:57 pm »
While erasing chip marking sounds funny, how is that worse than using custom chip markings that many non-chinese manufacturers do for their products?

It is there to prevent simple reverse engineering, or rather blatant copying that is reality in China...

Also I would like to point that phrase"poor software design" might mean software that doesn't work up to it's own specs, or to a software that was done to specs, but specs were not well designed.. I would say that most of chinese T&M equipment shows they have good engineers, but have only 10-15 years of experience making it as opposed to 60+ years for EU or US manufacturers... That shows in the fact that are capable of making good hardware, but not being able to "envision" and therefore design feature set, UI and such, to make instrument both powerful, easy to use, and "cool"...

Also in former USSR and China, mentality "function over form" was prevalent. It could have been ugly and hard to use, it didn't matter. If it did the job, operator was supposed to learn how to use it and live with it shortcomings..  So scope is not complicated, it is operator that is not smart enough...
Some of that mentality is still there, but slowly going away...

And I wouldn't say 20 years... More like 10, judging by the speed of learning so far... Also they buy knowledge and technology at a fast pace, to complement their own research...

 
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Online jleg

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #14 on: September 18, 2017, 09:33:09 pm »
And in a "professional" rather than "consumer" field?  Lenovo maybe, but they inherited a lot from IBM.
Huawei comes to my mind. Afaik they pretty rule the carrier network market, ask Ericsson, Nokia or Siemens... ;-)
 

Offline schopi68

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #15 on: September 18, 2017, 10:22:44 pm »
The A-Model has more software (remote-control) features enabled out of the box, a better slew-rate and higher frequency range to use. ;)

Banana-Plugs are not specified for 40 oder 60 Amps. Thats why they are not used in these kind of loads.

Regarding the Range-switch at 29:40: the resolution of the internal display is not changed when switching the range of the device. Terrible. So internal measurement is always done in the 40 Amps range (and not out of spec).

Would you like to see why i sent back my rigol DL3021A? Have a look at this:



(for further testing, or if somebody who owns this device would like to do some own testing, it would also make sense to put a serial power resistor of i.e. 10 Ohms between the load and the power supply. In the set up i used with only the wiring resistance the power supply does a lot of damping in the circuit)
 

Online mikeselectricstuff

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #16 on: September 18, 2017, 10:47:07 pm »
The A-Model has more software (remote-control) features enabled out of the box, a better slew-rate and higher frequency range to use. ;)

Banana-Plugs are not specified for 40 oder 60 Amps. Thats why they are not used in these kind of loads.
But most people won't be using them at full load most of the time. Omission is annoying.


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Online blackdog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #17 on: September 18, 2017, 11:19:19 pm »
Hi,


My big problem is, if Dave is correct, the use of de IRFP250 Mosfet, this Mosfet is NOT DC specified!
I know there are 6 of them, but it gives me the creeps.
I do NOT trust the SOA of this device...

Kind regards,
Blackdog
« Last Edit: September 18, 2017, 11:29:37 pm by blackdog »
 

Offline Rbastler

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #18 on: September 18, 2017, 11:29:07 pm »
Hi,


My big problem is, if Dave is correct, the use of de IRFP250 Mosfet, this Mosfet is NOT DC specified!
I know there are 6 of them, but it gives me the creeps.
I do NOT trust the SOA of this device...

Kind regards,
Blackodg

Waht do you mean with "not DC specified" ? That its made for switching applications only ?
On the Batronix website of the load http://www.batronix.com/versand/last/DL3021.html, it says the min voltage at the inputs must be 1V... Is that true ? I recall Dave discharging a battery down to sub 1V.

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Online blackdog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #19 on: September 18, 2017, 11:34:47 pm »
Hi Rbastlerm,

Yes, this is a Mosfet for switching applications, and yes, you can use it for DC, but when wil it blowup? no specs...
There is always a minimum voltage spec, mostly depended on how many Ampere used .

Kind regards,
Blackdog
« Last Edit: September 18, 2017, 11:38:40 pm by blackdog »
 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #20 on: September 19, 2017, 12:14:54 am »
Hi,


My big problem is, if Dave is correct, the use of de IRFP250 Mosfet, this Mosfet is NOT DC specified!
I know there are 6 of them, but it gives me the creeps.
I do NOT trust the SOA of this device...

Kind regards,
Blackdog
I've used tens of thousands of FETs (without the FBSOA in the datasheet) in DC.
You need to carefully select the model, verify the design, and test each and every unit. And use the proper FET technology, some older are better than the newer like Trenchfet and others.
The only ones failing the ones, where isolation was broken or it wasnt properly mounted on a heatsink.
It's 16x TO247 FETs for only 350W. That is about 21W/FET, with typical 0.9K/W junction to sink. I pushted TO220 much harder than this, its not even going to be warm. Unlike the stupid linear regulators they used.
 

Offline vlad777

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #21 on: September 19, 2017, 02:25:03 am »
I think you can use the knob, because it seems that the digits have underscore selector.
Mind over matter. Pain over mind. Boss over pain.
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Online blackdog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #22 on: September 19, 2017, 02:36:53 am »
Hi NANDBlog,  :)

Sorry, but I do think this is a crazy design, and if I see the oscillation phenomena in the schopi68 video  |O
This has to be a joke.

This Electronic Load is never tested the way it should, when is was "designed".
The phase margin is one of the first things you have to test, before production.
8 or 16 Mosfets they like problems there in China *grin*

Use some Linear Mosfets you wil be amazed and you need only two of them, but the price and the Rdson wil be a problem.
But 4 of these wil do the job : IXTH60N20L2

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Offline IanMacdonald

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #23 on: September 19, 2017, 02:46:24 am »
"My big problem is, if Dave is correct, the use of the IRFP250 Mosfet, this Mosfet is NOT DC specified!"

Eh? The specsheet says 180W dissipation. As usual this only applies if it's welded to the side of the Titanic as a heatsink with obligatory iceberg still in contact, but nevertheless I can't see why it's not 'DC rated' what ever that means.

http://www.datasheetcatalog.com/datasheets_pdf/I/R/F/P/IRFP250.shtml

It also has to be remembered that the temperature of a small heatsink on a device dissipating a watt or two can safely be higher than that of a large heatsink on a device dissipating tens or hundreds of watts. This is because the difference between the actual device temp and the external measurable temp will be less than for a device under high power.

LM317 handling a couple of watts - h/s at 80C, chip at 100C, OK.  8)

TO247 Mosfet direct mounted, handling 140W, h/s at 40C, chip at 180C .. about ready to pop.  >:(

BTW, Gandalf says whatever you do, don't touch the Eye button. His buddy Saruman did, and... 
« Last Edit: September 19, 2017, 03:09:44 am by IanMacdonald »
 

Online blackdog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #24 on: September 19, 2017, 02:55:13 am »
Hi IanMacdonald


Download this PDF: http://www.ixys.com/Documents/AppNotes/IXAN0061.pdf
Look @ page 8 figure 10 tipical switching Mosfet, <= Electro-Thermal Instability Boudary
Look at the dashed line and see the horror...

Kind regards,
Blackdog


PS

My Datasheet is from International Rectifier, but Fairchild shows some DC SOA, ST also  ;)
« Last Edit: September 19, 2017, 03:03:29 am by blackdog »
 

Offline Rbastler

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #25 on: September 19, 2017, 03:08:53 am »
Hi IanMacdonald


Download this PDF: http://www.ixys.com/Documents/AppNotes/IXAN0061.pdf
Look @ page 8 figure 10 tipical switching Mosfet, <= Electro-Thermal Instability Boudary
Look at the dashed line and see the horror...

Kind regards,
Blackdog


PS

My Datasheet is from International Rectifier, but Fairchild shows some DC SOA, ST also  ;)

I understand your point, but woudnt the load limit itself over the maximum power and therefore never get the six ? IRFP250N over that "electro thermal instability boundary" ?

Edit: Shoudnt the mosfets be viewed as one ? Therefore the graph would be extended in the amp axis. Threfore the instability zone would be far away ?
Just some ideas, that came to mind.
« Last Edit: September 19, 2017, 03:11:47 am by Rbastler »
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Offline nctnico

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #26 on: September 19, 2017, 03:20:46 am »
My big problem is, if Dave is correct, the use of de IRFP250 Mosfet, this Mosfet is NOT DC specified!
I know there are 6 of them, but it gives me the creeps.
I do NOT trust the SOA of this device...
That was my initial thought too but then I remembered Agilent/Keysight is using similar MOSFETs (like IRFP240 / IRF640) in their DC loads. It is not all bad but choosing the right MOSFET for a DC load isn't trivial.
« Last Edit: September 19, 2017, 03:24:44 am by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline schopi68

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Offline IanMacdonald

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #28 on: September 19, 2017, 03:41:18 am »
The modified SOA consideration only seems to apply at relatively high voltages. The datasheet for the IRFP250  says 'SOA is power dissipation limited' which I would assume means that derating is not required.  :-//

A point worth noting about power ratings which IXAN0061.pdf mentions, is that case-to-device temperature differences can change extremely quickly, of the order of tens of milliseconds. In other words, the chip has an extremely small thermal inertia. Thus, a sudden surge in dissipation can blow an already-hot device even though it did not last long enough to warm the heatsink measurably, and was not over the device's specsheet rating @25C.  :wtf:
« Last Edit: September 19, 2017, 03:43:22 am by IanMacdonald »
 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #29 on: September 19, 2017, 03:52:12 am »
Hi IanMacdonald


Download this PDF: http://www.ixys.com/Documents/AppNotes/IXAN0061.pdf
Look @ page 8 figure 10 tipical switching Mosfet, <= Electro-Thermal Instability Boudary
Look at the dashed line and see the horror...

Kind regards,
Blackdog


PS

My Datasheet is from International Rectifier, but Fairchild shows some DC SOA, ST also  ;)
I am well aware of the SOA, FBSOA and other sizing of FETs. I used SOT227 FETs, where they were required. They do 500W each with enough cooling. I also used FETs with and without DC in the datasheet in DC. They work, you just need to select the right one, and make sure they work. The IRFP250 is a solid choice for a DC load. It is used in other DC loads. It is used in audio amplifiers. It has been used for a long time. I personally did not test it, but judging by the amount of circuits using them in DC, it is probably safe.
The instability of the DC load:
It is certainly not trivial to tune the analog parst in these circuits, I know it first hand. Especially, if you have a lot of constrains, like frequency response and rise and fall times. It doesnt help, that it has to be able to do 1mA and lots of amps with the same parts. If you see these kind of oscillations, provide feedback, they will probably do a revision.
 

Offline Kleinstein

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #30 on: September 19, 2017, 04:23:55 am »
Most data-sheets for the IRFP250 don't specify DC operation, however this per se does not say it can not work. I have seen a Fairchild data-sheet that  actually did specify DC operation, even over the full range. However I am not sure it was the IRPF250 or IRFP250N.

The IRFP250 was a common type used in many audio amps. So it is not such an unusual choice, though more a cheap one. I would not worry so much about 40 A at low voltage (e.g. 5 V) but if at all with 150 V at 1 A. Turning off with a inductive source, could cause trouble - so some extra reserve on the voltage side would be good. I doubt they would use two FETs in a cascode mode each.

Why do they have 2 current ranges if there is only one shunt ? They can't use just 1 or 2 of the power stages - as even 4 A would be too much power at 100 V.

The other slightly odd thing is that I don't see high power resistors for current sharing.

Having the amplifiers lasered off for the amplifiers is really strange - I won't expect anything so special with this. The quality of the current reading is more limited by the shunt quality.
 

Offline Avacee

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #31 on: September 19, 2017, 04:29:34 am »
When DC load designs have been mentioned in the past the experts here usually suggest having a resister per MOSFET and individual feedback otherwise one MOSFET ends up taking all the current and suffering thermal runaway.
I couldn't see anywhere on Dave's video individual resistors so are all the MOSFETs fighting with each other or are Rigol solving the runaway issue?
Or am I showing my newbishness and a lack of understanding and 1 resistor with multiple MOSFETS is actually fine?
 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #32 on: September 19, 2017, 04:42:58 am »
When DC load designs have been mentioned in the past the experts here usually suggest having a resister per MOSFET and individual feedback otherwise one MOSFET ends up taking all the current and suffering thermal runaway.
I couldn't see anywhere on Dave's video individual resistors so are all the MOSFETs fighting with each other or are Rigol solving the runaway issue?
Or am I showing my newbishness and a lack of understanding and 1 resistor with multiple MOSFETS is actually fine?
No, you should have 1 resistor per FET. It is probably under the heatsink. Or bottom side. You see the isolation slots? So for sure, the trace from the Drain has to go under the heatsink. And there is a double opamp per FET pair.
 
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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #33 on: September 19, 2017, 05:36:54 am »
My big problem is, if Dave is correct, the use of de IRFP250 Mosfet, this Mosfet is NOT DC specified!

How can a MOSFET not be DC specified?

I've yet to see a MOSFET that can switch AC. :popcorn:

« Last Edit: September 19, 2017, 05:39:25 am by Fungus »
 

Offline MBY

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #34 on: September 19, 2017, 05:43:48 am »
Nobody noticed the "FERQ" value instead of "FREQ" in the tran-menu? Software feels like beta...
 

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #35 on: September 19, 2017, 06:04:00 am »
Hi,


Its like Kleinstein explaned, the shit happens if there are high voltages on de electronic load.
You can see it also in the document i refered to, there are no problems in the low voltage range.

Hi Fungus
How can a MOSFET not be DC specified?
Sorry i'am a Dutch dyslexic monkey, i do my best to make it so understandable as posible  :D
This load is specified for 150V! so the SOA is realy important at these voltages.

Kind regards,
Blackdog
 

Offline nctnico

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #36 on: September 19, 2017, 06:17:40 am »
When DC load designs have been mentioned in the past the experts here usually suggest having a resister per MOSFET and individual feedback otherwise one MOSFET ends up taking all the current and suffering thermal runaway.
I couldn't see anywhere on Dave's video individual resistors so are all the MOSFETs fighting with each other or are Rigol solving the runaway issue?
I'd get the service manuals for the Keysight N3304 DC load module. This has full schematics and from a functional point of view it looks much like this Rigol DC load.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Offline mcinque

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #37 on: September 19, 2017, 06:24:37 am »
ok we can argue if they can improve or not, that's right. Interface, software, etc. Everyone can improve.
But I ask myself what we're discussing here if they repeated almost the SAME lr heatsink noob mistake they had YEARS ago with the dp832?! :palm:
I can't believe it. Really. It's ridiculous.
I'm basically still a rookie and because of this, even with the best intentions, I often say bullshit :)
 

Online Fungus

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #38 on: September 19, 2017, 06:42:59 am »
Hi Fungus
How can a MOSFET not be DC specified?
Sorry i'am a Dutch dyslexic monkey, i do my best to make it so understandable as posible  :D
This load is specified for 150V! so the SOA is realy important at these voltages.

That one's rated to 200V so there's a little bit left over.

What voltage would you be happy with? Where do you think a manufacturer should draw the line if they think their customers are going to put more than 150V into 150V devices? 250V? 300V? :-//

In reality I suspect not many people are going to go near 150V on a 200W device. It would be interesting to see if the 'A' version uses different MOSFETs.
 

Offline Jay_Diddy_B

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #39 on: September 19, 2017, 07:50:06 am »
Hi group,

Since we are friends, I will share a few pictures of the inside of an HP6060A load. This is a 60V 60A 300W load.

Input Terminals



MOSFETS






I removed the clamp on a pair of the MOSFETs.


There are a total of 8 MOSFETs, four on each side of the tunnel. Each MOSFET is an IRF540. The heatsink is at the same potential as the positive input.


There is one sense resistor and one op-amp controller per MOSFET. You can you can see the sense resistors, but too hard to photograph. The resistors are in the center of the tunnel.

Big Picture



Look at all that thru-hole goodness !!!



Regards,

Jay_Diddy_B
« Last Edit: September 19, 2017, 07:59:23 am by Jay_Diddy_B »
 

Offline thm_w

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #40 on: September 19, 2017, 08:22:26 am »
The A-Model has more software (remote-control) features enabled out of the box, a better slew-rate and higher frequency range to use. ;)

Banana-Plugs are not specified for 40 oder 60 Amps. Thats why they are not used in these kind of loads.
But most people won't be using them at full load most of the time. Omission is annoying.

I think there is a valid concern that someone will plug in some banana leads and run 60A through them. They will then proceed to catch fire. Although its probably a simple cost saving measure, as TTI offers an 80A load with some kind of banana terminals: https://www.aimtti.us/product-category/electronic-loads/aim-ld400series

They could definitely sell/include a small adapter PCB though, to convert the huge terminals to standard banana jacks. Would be easy for someone to design one.

Hi group,
Since we are friends, I will share a few pictures of the inside of an HP6060A load. This is a 60V 60A 300W load.

So the HP 60V 60A 300W load is using 100V 28A*8 FETs IRF450.
Rigol is 150V 40A 200W load using 200V 30A*8(?) FETs IRFP250N.
30% vs 60% voltage margin, but who knows if the 100V choice was intentionally selected or, just the closest voltage spec that happened to exist. Either way the component choice doesn't seem unreasonable in comparison.

Also as someone mentioned in the YT comments, the non-A version does not have color coding. In the case of the DP832/DP832A power supplies its the same, the cheaper one uses monochrome colors only on the LCD and does not have colored buttons. I agree its an odd choice, but that's their way of differentiating the market segments, and its something that is partially "unhackable", unless you want to print a new front sticker.
« Last Edit: September 19, 2017, 09:13:51 am by thm_w »
 

Offline nctnico

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #41 on: September 19, 2017, 08:34:41 am »
I have used these type of binding posts (rated 200A) for a project. They also accept 4mm banana plugs which is handy but ofcourse you can't have 200A through a banana lead.
« Last Edit: September 19, 2017, 08:38:11 am by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Smokey

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #42 on: September 19, 2017, 05:20:49 pm »
What OPP and OCP stand for is buried pretty deep in the manual.

Apparently Rigol engineers are fans of both RoboCop and Naughty By Nature...
You down with electronics loads with OPP?????
 

Online blackdog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #43 on: September 19, 2017, 05:41:32 pm »
Hi,


Let put the HP 6080 DC load in perspective...

Max. 60V and Max 300-Watt, thats 5-Ampere and it uses 8x IRF540 parts.
5-Ampere trough 8 Mosfets is a little more than 600mA a Mosfet! at 60% of the Vds. (Rigol use 80% of the max. Vds and that is bad for de max. SOA)
The DC SOA spec of the ST brand says about 1.7-Ampere at 60V, looks like HP use a better safety margin :-)
And HP have to keep the IRF540 realy cool, 300-Watts/8 is 37.5 Watt a Mosfet, i think at full load it will sound like a F16  :-DD

There the is a big difference between the ST IRF540 and the IRF IRF540, ST part looks to have a mutch better SOA...
So many different specs from brand to brand, that gives me the creeps in this aplication.

Kind regards,
Blackdog

 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #44 on: September 19, 2017, 06:30:05 pm »
So many different specs from brand to brand, that gives me the creeps in this aplication.
Well, just dont design and review DC loads then, because you are obviously not comfortable with it.
I bet you, that Rigol, HP/Agilent/Keysight tested orders of magnitude more number of FETs, under full load for longer time, than the people writing the datasheet. I did for some parts, that's for sure. There are devices, they've been operating for decades, some of them under full load, and you run around, hands in the air, shouting "Its gonna blow any minute! Everyone run! Its not in the datasheet!"
 
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Online blackdog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #45 on: September 19, 2017, 07:09:31 pm »
Hi NANDBlog,

Maybe its better that you try to understand wat i try to say...
Like Rigol is using the IRFP250 much closer to there Max. Vds than HP in there 6060A, more change it wil fail.

And i think HP, like a told before, uses a better savety marging and i trust the HP design team more than Rigol.
Take al look at al the big differences for the datasheet for the IRF540 from different brands, these are not the same Mosfet!
So, if you blow the power section witch part are you gonna use? ( of course the HP component for the 6060A  :) )

Design a DC load for yourself, no problemo, if yo want to do production for 3000 units, are you gonna use a Fairchild part?  or ON semi (if these still exist)
Can i replace it with a IRF part (Vishay) or ST, wat about the internal capacitors in de Mosfet, every brand it is different. (maybe thats the source of the instability of the Rigol  :) )
Do i have to use more compensation so that i can use all brands IRF250, do i still reach my power bandwith...

Yes! these IRF250 Mosfets are cheap, but can also be problematic to use, effery brand tells you to read an respect the datasheet data.
There are to many electronic designers wo are not enough aware of SOA problems, or thermal problems like the linear regulators in the Rigol products.
Or are pushed by the braindead marketing department, to make stupid decisions. (Rigol buttons, text, linear regulators, wiring in my Rigol DP832A Power Supply, 470uF! over the output for a 3A Power supply, van noise, etc.)

I like to test a Rigol DC load fo a day on 160V full load at 40C room temperature, lets see what happen...

Kind regards,
Blackdog

 

Offline lukier

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #46 on: September 19, 2017, 07:23:45 pm »
I too think that the SOA argument is making mount of a molehill.

All cheap (BK,ITech,Maynuo etc) DC loads use IRF540. Agilent as well, also in N3302A (see service manual). It's fine as long as it is characterized and tested.

What I find "interesting" with the Rigol DL3021 load is the amount of computing power there. iMX for the comms and UI - OK, but why CPLD for the front panel and big FPGA, just to read ADC samples or set the DAC.

Also, maybe I missed that from Dave's video. Where is the isolation between the iMX/UI and the FPGA/ADC/DAC? Is this load mains earth referenced? That would be rather odd.
 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #47 on: September 19, 2017, 09:55:08 pm »
if yo want to do production for 3000 units, are you gonna use a
I made larger productions than that, with FETs with absolutely no DC rating. Yes, in DC mode. You are in write only mode.
 

Online Fungus

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #48 on: September 19, 2017, 10:38:23 pm »
Hi NANDBlog,

Maybe its better that you try to understand wat i try to say...
Like Rigol is using the IRFP250 much closer to there Max. Vds than HP

It's within the manufacturer's specification.  :-//

(by 25% - quite a large margin, really)

This load probably won't be used at 150V very often simply because it doesn't have enough Watts for people who usually work with 150V.

(I suspect most people who use this load will be more interested in amps than volts)

 

Online blackdog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #49 on: September 19, 2017, 10:50:46 pm »
Hi  NANDBlog,  :)

You are in write only mode
Oooo, please give me the spec's of what you build, and how it is used fo years...
I have no problems with a IRF540 on relative low DC voltages and high power.

If you look at the datasheets, if there is a DC spec, its at 25C case temperature, that wil be a hell of a heatsink.
And yes, i will give you that the IRF540 is better than most of the modern parts voor DC. :-)

Dit you read my reply #24 about the IXAN0061 application note?

Kind regards,
Blackdog
 
 

Online blackdog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #50 on: September 19, 2017, 10:59:52 pm »
Hi Fungus,

I have no problems is te Rigol is testing a 24V battery at a high current, but its spect at 150V.
The SOA becoms more an more a problem, in the higer part of the Vds.
Somone already told here, that older parts are better than the modern switching Mosfets, just be careful...

Read the IXAN0061 application note and some other SOA problems with Mosfets, use google to find the info.

Kind regards,
Blackdog
 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #51 on: September 19, 2017, 11:16:09 pm »
Hi  NANDBlog,  :)

You are in write only mode
Oooo, please give me the spec's of what you build, and how it is used fo years...
I have no problems with a IRF540 on relative low DC voltages and high power.

If you look at the datasheets, if there is a DC spec, its at 25C case temperature, that wil be a hell of a heatsink.
And yes, i will give you that the IRF540 is better than most of the modern parts voor DC. :-)

Dit you read my reply #24 about the IXAN0061 application note?

Kind regards,
Blackdog
Does it matter? It was a different FET, different cooling, different voltage.
Yes, I read your reply. You posted an application note about FBSOA. I mentioned FBSOA a few posts earlier. I've read that document years ago. Yes FETs fail at high voltages, that happens.
But for a FET to fail, you need to have 1) high temperature 2) drive it above below the inflection point* 3) high power 4) usually high voltage

If they properly tested the design, and it doesnt fail, it is not going to fail for years. It is only 25W  per FET. That's nothing. If it would be a bad design, this is something they would have noticed by now, because they would have a double digit failure rate during testing.
« Last Edit: September 20, 2017, 02:54:12 am by NANDBlog »
 

Online Fungus

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #52 on: September 20, 2017, 12:22:36 am »
that wil be a hell of a heatsink.

Yes, it looked very big to me. About 20% of the internal volume of the device.
 

Offline schopi68

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #53 on: September 20, 2017, 12:39:35 am »
But for a FET to fail, you need to have 1) high temperature 2) drive it above the inflection point* 3) high power 4) usually high voltage

Isn't driving below the inflection point the critical situation?

According to ON Semiconductor AND8119/D "The thermal-runaway situation occurs when you use large devices at low current-limit settings."
 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #54 on: September 20, 2017, 01:03:45 am »
But for a FET to fail, you need to have 1) high temperature 2) drive it above the inflection point* 3) high power 4) usually high voltage

Isn't driving below the inflection point the critical situation?

According to ON Semiconductor AND8119/D "The thermal-runaway situation occurs when you use large devices at low current-limit settings."
I dont think that is the right document.
The quote is right though. One FET is a lot of small FETs in parallel. If they get warm, the Rds of each small fet will change, based on their temperature. If you increase the temperature, below a certain Vgs, they will conduct less, above a certain Vgs they will conduct more. If you operate the FET above that Vgs, then it could thermal runaway.
It is hard to explain these, since these are 5 parameters, Vgs, current, temperature,Rds, Time, and it is different for the small FETs. Basically all the current and the dissipation will be concentrated into a small region, because the Rds changes. And then that part of the silicon will overheat, and fail. And then the rest will take over, and fail too.
blackdog is right about this, and yes, Figure 10 of his appnote describes this.
http://www.ixys.com/Documents/AppNotes/IXAN0061.pdf
But notice two things. One is the case temperature, which is 90 degrees. The other, that the graph goes to 1000V and 30A. And you also need to notice, that the graph is actually wrong, as it would allow to run the FET at 150V 2A but not 150V 0.1A.
 

Offline schopi68

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #55 on: September 20, 2017, 02:18:33 am »
According to ON Semiconductor AND8119/D "The thermal-runaway situation occurs when you use large devices at low current-limit settings."
I dont think that is the right document.

What is wrong with this document?

The quote is right though. One FET is a lot of small FETs in parallel. If they get warm, the Rds of each small fet will change, based on their temperature. If you increase the temperature, below a certain Vgs, they will conduct less, above a certain Vgs they will conduct more. If you operate the FET above that Vgs, then it could thermal runaway.
It is hard to explain these, since these are 5 parameters, Vgs, current, temperature,Rds, Time, and it is different for the small FETs. Basically all the current and the dissipation will be concentrated into a small region, because the Rds changes. And then that part of the silicon will overheat, and fail. And then the rest will take over, and fail too.
blackdog is right about this, and yes, Figure 10 of his appnote describes this.
http://www.ixys.com/Documents/AppNotes/IXAN0061.pdf

I can not see VGS in Figure 10. ;)

But the figures in the app-note i've listed shows VGS and the behaviour is described in the text. From what i can read there, the behaviour seems to be the opposite than the one you described.   :-// At a gate-to-source Voltage greater than that of the inflection point an increase of the temperature will decrease the drain current.
 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #56 on: September 20, 2017, 02:53:41 am »
According to ON Semiconductor AND8119/D "The thermal-runaway situation occurs when you use large devices at low current-limit settings."
I dont think that is the right document.

What is wrong with this document?
AND8119 is a 2W bias power supply design, and there is nothing in it about thermal runaway.

But the figures in the app-note i've listed shows VGS and the behaviour is described in the text. From what i can read there, the behaviour seems to be the opposite than the one you described.   :-// At a gate-to-source Voltage greater than that of the inflection point an increase of the temperature will decrease the drain current.
Yes, of course, you are right. It is below. Above is the "lot of current" territory.
 

Offline Kleinstein

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #57 on: September 20, 2017, 03:36:25 am »
The thermal instability problem also depends on the thermal properties on the chip. On the chip the small FETs are thermally coupled reasonably well, but not perfect. Up to a certain power level the thermal coupling can still prevent a thermal runaway.

The change in local power depends of the temperature dependence of the gate voltage for a given current, the trans-conductance (S) and the drain source voltage. This directly shows that higher voltage are the difficult range. In the low current range relevant here, the dU_GS/dT is not so different across vertical Fets, something in the - 4 mV/K range. So from the heat source part one is usually in the region that favors power localization - it is just a question if this is bad enough to overcome thermal coupling.

The main parameter one can choose is getting a FET with a low trans-conductance (S) for a given die size / thermal setup. One finds low S values usually with old MOSFETs and higher voltage types. Modern switching types on the contrary are made for a large S for a given die size -  so they are generally not a good choice.

Another parameter is how homogeneous the chip is to start with - if there are larger variations to start with one can have a MOSFET that can work perfectly as a switch but could fail in linear mode. To be sure it would need individual testing of the FSOA performance. With just standard parts, there is a certain chance for failure.

To finally make the choice of FETs even worse, there are data-sheets that show wrong DC FBSOA curves, that suggest they would be suitable for power dissipation, even if the parts would very likely fail. This is because sometimes SOA curves are only derived from transient thermal response curves and this ignored the possible thermal runaway. If there are transient thermal response curves just before a SOA curve with no brake to indicate the thermal instability limit, one should be suspicious about the SOA.
 

Offline Jay_Diddy_B

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #58 on: September 20, 2017, 05:10:52 am »
Hi,
Here are a few words and pictures of my understanding of the SOA issues with MOSFETs.

1) Older MOSFETs with low Gm are more robust.
Have to be careful that the MOSFET has not been redesigned, die shrink, on a modern process.
Older planar MOSFETs are the best.

2) MOSFETs with high gate threshold voltage are more robust

3) MOSFETs that have been optimized for switching, low gate charge perform badly.

The fundamental reason is that the for a given gate source voltage the drain current will increase with temperature. If the device is not uniform then a small area of the device will have local heating and there will be thermal runaway from the hotspot leading to catastrophic damage.



There will be an SOA curve on the datasheet.
If it looks like this:



It includes the are of thermal instability, indicated by the breakpoints on the lines. This is fairly reliable.

If the SOA curve looks like this:



This datasheet was generated before the interest in thermal instability or the part does not suffer from thermal instability. This is tough to decide and the parts have to be tested.
I would be very cautious of the datasheets so no thermal instability. I would not assume that company S is better than company I.

Testing

I have done some testing to verify SOA curves on a few MOSFETs. Here are some of the results:







Testing the IRFP250

I have not tested the IRFP250 (N). It would be interesting to see how it performed at 40W and 150V.
(May be if I get a minute or two and I want sacrifice a few MOSFETs)

My gut tells me that it should perform reasonably well. It is an older part, it has not really being optimized for switching. I don't know if has been 'improved' by die shrinks which would reduce its reliability in the linear region.


Regards,

Jay_Diddy_B
« Last Edit: September 20, 2017, 05:12:43 am by Jay_Diddy_B »
 
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Offline samofab

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #59 on: September 20, 2017, 06:09:47 am »
Slightly off the FSOA topic... I think that Dave's unit is fully optioned version which is closer to DL3021A.. (LAN, digital IO, etc..)
See screenshot attached.
 

Offline Hydrawerk

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #60 on: September 20, 2017, 07:26:51 am »
What are your opinions on GW Instek electronic loads like PEL-3000E?
http://www.gwinstek.com/en-global/products/Electronic_Loads/DC_Electronic_Loads/PEL-3000E
Is it better than Rigol?
GW Instek has been producing DC electronic loads for a long time, there was PEL-300 some time ago.
http://www.gwinstek.ca/products/742/300w-programmable-dc-electronic-load
« Last Edit: September 20, 2017, 07:32:09 am by Hydrawerk »
Amazing machines. http://www.youtube.com/user/denha (It is not me...)
 

Offline FrankBuss

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #61 on: September 20, 2017, 07:54:52 am »
In my Siglent SPD3303D power supply there is the same problem for an otherwise good device: no velocity for the knob and it is even worse, because it doesn't have a numeric input, and if I turn it fast, sometimes it goes even back (maybe they didn't sample it with a high sample rate and a state machine, but used an interrupt for one pin of the quadrature encoder, which you shouldn't do). And firmware update didn't work. I guess they need some more years experience until they get to the level of something like my Agilent scope for the GUI. Hopefully the price doesn't increase then as well.

But this looks like a serious limitation for the battery app. In the video it sounded like it can do only a constant current discharge test in this mode?
So Long, and Thanks for All the Fish
 

Offline Rbastler

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #62 on: September 20, 2017, 03:52:01 pm »
But this looks like a serious limitation for the battery app. In the video it sounded like it can do only a constant current discharge test in this mode?

That sucks, yes. But its something fixable in firmware, which I think they are going to fix because a lot of people will complain.
http://rbastlerblog.jimdo.com/
Gamma spectrometer works. Now some yellow crystals need regenerating and testing.
 

Offline Worsdier

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #63 on: September 20, 2017, 03:57:07 pm »
But this looks like a serious limitation for the battery app. In the video it sounded like it can do only a constant current discharge test in this mode?

That sucks, yes. But its something fixable in firmware, which I think they are going to fix because a lot of people will complain.

They told me that other discharge modes will be added in a firmware update, but that update was scheduled for the end of last month and it didn't materialize.
 

Offline schopi68

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #64 on: September 20, 2017, 06:34:44 pm »
What is wrong with this document?
AND8119 is a 2W bias power supply design, and there is nothing in it about thermal runaway.


Sorry - i've made a typo. AND8199/D would be the right document.
https://www.onsemi.com/pub/Collateral/AND8199-D.PDF
 

Offline schopi68

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #65 on: September 20, 2017, 07:10:01 pm »
In my Siglent SPD3303D power supply there is the same problem for an otherwise good device: no velocity for the knob ...

to be honest: i really hate devices with velocity in the knobs.  :-[ It happens so often that i want to increase some value by a small amount - and when turning just a little bit too much it makes huge steps into an area of damage.

So the rigol-solution (they are using the same principle i.e. in their DG1000Z function generators line) where you can preselect the decimal place where you do your changes is not really a bad one. Sometimes it is annoying too - but you always have full control.

In my opinion the DL3021 is not a really bad device and it is much better in many points than i.e. maynuo, BK or itech devices. But it has some design flaws that may be a showstopper for some people (for me it was the 3,5 MHz oscillation observed... some data that were completely out of spec ... and the huge size of the device compared to its load capabilities).
 

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #66 on: September 20, 2017, 07:18:01 pm »
In my Siglent SPD3303D power supply there is the same problem for an otherwise good device: no velocity for the knob ...

to be honest: i really hate devices with velocity in the knobs.  :-[ It happens so often that i want to increase some value by a small amount - and when turning just a little bit too much it makes huge steps into an area of damage.

It's good if it's implemented well, unfortunately it often isn't.
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Offline schopi68

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #67 on: September 20, 2017, 07:55:59 pm »
In my Siglent SPD3303D power supply there is the same problem for an otherwise good device: no velocity for the knob ...

to be honest: i really hate devices with velocity in the knobs.  :-[ It happens so often that i want to increase some value by a small amount - and when turning just a little bit too much it makes huge steps into an area of damage.

It's good if it's implemented well, unfortunately it often isn't.

I've never seen a good implementation (for my needs). ;)
 

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #68 on: September 21, 2017, 11:17:40 pm »
I have to admit that my confidence in Rigol is severely shaken, the scope i have is nice but clearly they went bananas over scope design as it's the first and most desired product, but can they make anything else properly? maybe not.
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Offline Kleinstein

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #69 on: September 22, 2017, 08:04:46 pm »
The heat sink temperature at some 80 C is not such a disaster - they may fix it in future versions. Also the 240 V volts in Australia give the regulator is little more stress than 230 V in Europe.

Otherwise the circuit looks a little odd in some places, but not bad. For the software there are a few more features they might be able to add. What makes my scratch the hat :-// a little are the specs for the given HW.
Instead of 200 W, 40 A / 150 V and 0.05% accuracy, the HW looks more like suitable for
400W, 60A / 80 V and 0.2 % accuracy. Still a nice load, but kind of a different model.

If you want real battery testing, one would use a different gear in most cases anyway. More like multi channels and usually lower power / lower voltage.

It might be interesting how good / fast the current read back is.
 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #70 on: September 22, 2017, 08:46:10 pm »
If you want real battery testing, one would use a different gear in most cases anyway. More like multi channels and usually lower power / lower voltage.
I concur. The battery tester I've worked on had 80 channels, and much higher accuracy for voltage and current. Capacity testing and coulombic efficiency requires very accurate equipment. This tester is fine to determine, wheter that 5 year old 12V battery is still holding some charge or not, or the new battery you bought has the claimed capacity.

It might be interesting how good / fast the current read back is.
You made me take a second look at it.
The shunt is isabellenhütte BVS 0.0005Ohm, which has a typical 50ppm/K tempco, but the 0.0005Ohm version has a typical 70ppm tempco. And the spec for the rigol is 50ppm/K.
And they dont include the tempco of the AFE. No way for it to be within that spec.
They also send 40A through that shunt, so self heating is about a watt. And they give 1000PPM (equivalent of 20K self heating) specification for full scale. I'm sorry, but those accuracy specifications are just not realistic. You cannot just take a number from one datasheet and use that for your specification. In the video Dave measures it out of spec (around 30 minutes). No wonder why.
 

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #71 on: September 22, 2017, 10:30:34 pm »
In the video Dave measures it out of spec (around 30 minutes). No wonder why.

Well, it is not out of spec. Dave is making the small mistake of assuming that the current readback has the same accuracy than the current setting. But the device does not switch the measurement range when switching the input range - even in the 4A setting range the readback range is still 40A.

Readback accuracy is ±(0.05%+0.05%FS). So the allowed readback reading for 1A would be 0.98A to 1.021A. Dave hat a measurement of 0.9977A - so the device is full within spec.

That the current readback range is not switched down with the current setting range is a shame. One of the real big showstoppers in my opinion for this device (and something that is not software-fixable). None of the big competitors is doing so.

There are so many users of this devices that want to characterize batterys - therefore an exact low current measurement is neccessary.
 
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Offline thm_w

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #72 on: September 23, 2017, 07:37:47 am »
You made me take a second look at it.
The shunt is isabellenhütte BVS 0.0005Ohm, which has a typical 50ppm/K tempco, but the 0.0005Ohm version has a typical 70ppm tempco. And the spec for the rigol is 50ppm/K.
And they dont include the tempco of the AFE. No way for it to be within that spec.
They also send 40A through that shunt, so self heating is about a watt. And they give 1000PPM (equivalent of 20K self heating) specification for full scale. I'm sorry, but those accuracy specifications are just not realistic. You cannot just take a number from one datasheet and use that for your specification. In the video Dave measures it out of spec (around 30 minutes). No wonder why.

I agree you can't just take numbers from the datasheet, and that could be what they've done here.
But look at the temperature graph for Manganin, the typical response is 17ppm/K, and worst case is 50. So maybe ~24ppm typical, for the 0.0005 ohm version. Its not unusual to use the typical value and not worst case.

Also, I seriously doubt they have done it here, but they could do a full temperature characterization and calibrate it out in software right? But there is no temperature sensor near that shunt that I see.
 

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #73 on: September 23, 2017, 10:32:06 am »
You made me take a second look at it.
The shunt is isabellenhütte BVS 0.0005Ohm, which has a typical 50ppm/K tempco, but the 0.0005Ohm version has a typical 70ppm tempco. And the spec for the rigol is 50ppm/K.
And they dont include the tempco of the AFE. No way for it to be within that spec.
They also send 40A through that shunt, so self heating is about a watt. And they give 1000PPM (equivalent of 20K self heating) specification for full scale. I'm sorry, but those accuracy specifications are just not realistic. You cannot just take a number from one datasheet and use that for your specification. In the video Dave measures it out of spec (around 30 minutes). No wonder why.

I agree you can't just take numbers from the datasheet, and that could be what they've done here.
But look at the temperature graph for Manganin, the typical response is 17ppm/K, and worst case is 50. So maybe ~24ppm typical, for the 0.0005 ohm version. Its not unusual to use the typical value and not worst case.

Also, I seriously doubt they have done it here, but they could do a full temperature characterization and calibrate it out in software right? But there is no temperature sensor near that shunt that I see.

Quote
YOU NORMALLY USE MANGANIN® AS RESISTANCE ALLOY IN THE RESISTORS. THE TEMPERATURE COEFFICIENT OF MANGANIN® IS SPECIFIED WITH < ± 10 PPM/K. WHY DO YOU MOSTLY SPECIFY YOUR SMD RESISTORS < ± 50 PPM/K ON THE DATA SHEETS?
For a two-wire, the TC of a component is comprised of the TC of the resistance material (e. g. Manganin®) and the not completely avoidable influence of the supply line or bonding. For that reason we usually specify the TC of a two-wire with < 50 ppm/K.
I came to trust their specifications and products. It is conservatively specified, 99% of the products will be much better than the specification, but then you get one or two, which isnt. But this is not my only issue. The specification (by rigol) is very very optimistic, and to get similar results, I had to use a magnitude better components. I give you an example. The Agilent 34465A has worse (tempco) specification with a better shunt, on the 1A range. And the Agilent doesn't have the self heating issues with 40A of current. In fact I would bet money on this: It wont be anywhere near the specification at 40A.
 

Offline Jay_Diddy_B

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #74 on: September 23, 2017, 10:49:46 am »
Hi,

Here are extracts from datasheets.
First from the Agilent 6060B load (first class load) we have:



And from the current range on the 34470A DMM (very high quality DMM):



The number is percentage of reading plus percentage of range.

The Rigol DL3021 load specifications are:



Rigol is claiming better accuracy, same temperature coefficient, as the Keysight 34470A on the 10A range.




Jay_Diddy_B
« Last Edit: September 23, 2017, 10:58:45 am by Jay_Diddy_B »
 

Offline k4rlhp

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #75 on: September 25, 2017, 08:54:31 pm »
Despite the teardown not being a be-all-end-all review, it still begs the question...
Is the rigol DL3021 really so bad that you should not buy it?

Reading through the posts here, this is the impression I get.
I couldn't care less about reverse italic or illuminati buttons looking odd if the basic functionality is okay and no dealbreaker artefacts are present. The oscillations demonstrated in one of the forum videos are worrysome in that department.

The alternatives, in this price category and functionality range we mostly have no-name clones on ebay and the likes of Itech IT8500 series. Comparatively, Rigol has its own support and provides firmware updates. So, what is a good alternative then?

Dave mentions Itech also in the BK prescision 8601 review.
I have been postponing purchasing the BK8601 in hopes that something cheaper but still decent will come along, including support from a known company. Missing the direct readout of Wh is a major omission on BK (for me), this why I have postponed the BK. Sure, there is a workaround but for that money i expect more. The RigolDL3021 was really good news on that part....


 

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #76 on: September 25, 2017, 09:28:24 pm »
I have to admit that my confidence in Rigol is severely shaken, the scope i have is nice but clearly they went bananas over scope design as it's the first and most desired product, but can they make anything else properly? maybe not.

I do like the DP832 and DM3068 very much, no issues or complaints so far.
I wound'nt say may confidence in Rigol is severely shaken but it certantly made me think again, if that e-load is good for my purposes and if Rigol is the only real good deal here. I think it still is though, because there arent valid alternatives for me, but I dont have the good feeling when thinking of buying it, I had with other Rigol gear.
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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #77 on: September 26, 2017, 03:35:58 am »
The heat sink temperature at some 80 C is not such a disaster - they may fix it in future versions. Also the 240 V volts in Australia give the regulator is little more stress than 230 V in Europe.

Quote
Maximum AC voltage today     : 250.70 volts
 

Offline mcinque

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #78 on: September 26, 2017, 07:30:57 am »
For me Rigol has simply missed price vs specs. If the load had the same price/specs as the dp832 (even with his issues) they would have take the market for hobbists/entry level gear. Instead, they made something that isn't good enough and, most of all, it's overpriced. It can't beat Maynuo for me, both for hardware and software.
« Last Edit: September 26, 2017, 07:33:07 am by mcinque »
I'm basically still a rookie and because of this, even with the best intentions, I often say bullshit :)
 

Offline SharpEars

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #79 on: September 29, 2017, 12:24:07 pm »
The cheap obsolete $0.60 Chinese fake MOSFETs they use in the electronic load, IRFP250n are not even characterized for DC operation or even operation beyond a 10 ms pulse, correct me if I am wrong here.

Good luck with the longevity aspect of this electronic load, since we don't even know if they are operating the MOSFETs in their safe operating area or if there even is a safe DC operating area:



They should have spent several dollars per MOSFET, used fewer of them, and gotten MOSFETs that are characterized to DC like the Linear L2 series from IXYS.

For example, the IXYS IXTP80N075L2-ND go for $3.20 in quantity (probably much less B2B) and are characterized all the way down to DC (not to mention have better characteristics being also 30 Amp MOSFETS):




« Last Edit: September 29, 2017, 01:26:50 pm by SharpEars »
 

Offline NANDBlog

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #80 on: September 29, 2017, 07:10:28 pm »
The cheap obsolete $0.60 Chinese fake MOSFETs they use in the electronic load, IRFP250n are not even characterized for DC operation or even operation beyond a 10 ms pulse, correct me if I am wrong here.
This was only discussed for 4 pages now.
 

Offline schopi68

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #81 on: October 04, 2017, 07:05:24 pm »
For me Rigol has simply missed price vs specs. If the load had the same price/specs as the dp832 (even with his issues) they would have take the market for hobbists/entry level gear. Instead, they made something that isn't good enough and, most of all, it's overpriced. It can't beat Maynuo for me, both for hardware and software.

Hardware on the Maynuo is something i would not throw into the discussion. In my opinion the Maynuo is 20 years back. No isolation from the rear panels, no specs about the maximum isolation voltages above ground, no interfaces more than RS232... unspecified slew-rates and overshot problems.

« Last Edit: October 05, 2017, 02:52:36 am by schopi68 »
 

Offline ass20

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #82 on: November 01, 2017, 04:21:12 am »
hi
 what is adc and dac used in rigol load ?
 

Offline mcinque

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #83 on: November 01, 2017, 07:39:06 am »
Hardware on the Maynuo is something i would not throw into the discussion. In my opinion the Maynuo is 20 years back. No isolation from the rear panels, no specs about the maximum isolation voltages above ground, no interfaces more than RS232... unspecified slew-rates and overshot problems.
So Maynuo is not the perfect load and has his limits (so the BK ones and other clones), but does this change anything about the Rigol as acceptable load with all the issues we're discussing here?
I'm basically still a rookie and because of this, even with the best intentions, I often say bullshit :)
 

Offline Rbastler

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #84 on: November 02, 2017, 08:45:27 am »
For me Rigol has simply missed price vs specs. If the load had the same price/specs as the dp832 (even with his issues) they would have take the market for hobbists/entry level gear. Instead, they made something that isn't good enough and, most of all, it's overpriced. It can't beat Maynuo for me, both for hardware and software.

Hardware on the Maynuo is something i would not throw into the discussion. In my opinion the Maynuo is 20 years back. No isolation from the rear panels, no specs about the maximum isolation voltages above ground, no interfaces more than RS232... unspecified slew-rates and overshot problems.

But you pay way less for a Maynuo, than a comparable "name" brand. So I'd say thats part for the cause. I got no issues with it. Can't expect everything for 275€ delivered. (Maynuo 9710 from a Chinese seller with German Stock).
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Offline schopi68

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #85 on: November 02, 2017, 10:52:03 pm »
Hardware on the Maynuo is something i would not throw into the discussion. In my opinion the Maynuo is 20 years back. No isolation from the rear panels, no specs about the maximum isolation voltages above ground, no interfaces more than RS232... unspecified slew-rates and overshot problems.

But you pay way less for a Maynuo, than a comparable "name" brand. So I'd say thats part for the cause. I got no issues with it. Can't expect everything for 275€ delivered. (Maynuo 9710 from a Chinese seller with German Stock).
[/quote]

When buying in the chinese market the DL3021 has a list-price of 388€ - not such a big difference.

And if you are going to the Maynuo M98-Series you will pay much more. A M9812 will cost around 500€.
 

Offline Wolfgang

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #86 on: November 09, 2017, 06:14:40 am »
Hi Dave,

I saw your review and it made me reconsider my idea to get one of those. I asked RIGOL about what they think about your findings and if there were any plans to fix some of them and what timeframe would be needed for that.
When I remember your review of the DP832A they reacted to your critique and redesigned and improved the instrument, so why not the same here ?

The reply by RIGOL was that they are not OK with your conclusions, and they wrote you a mail (not published).

My questions:
- will there be a follow-up on the issues described in your video ?
- Are there new facts I need to consider ?

Best regards
  Wolfgang
 

Offline schopi68

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #87 on: November 09, 2017, 09:29:25 pm »
Hmm... interesting to see (that the do react sometimes).
I made the youtube-video where i showed the oscillation of the DL3021A some time ago primarily to send it to the Rigol-Support. Up to now i did not even get a response from them about the situation shown there (what has been the main reason for me to publish this video some time later here to the public).
 

Offline Houseman

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #88 on: December 04, 2017, 09:41:46 am »
Hi folks.
I have read all your comments and are astonished how much once can learn from different points of view.
By the way a breaking question out from investigation.
Where can I find those beefy red and black cables (tagged I partially see BK precision) shown in minute: 28:30?
Any help would be very appreciated.
And thanks all.
My respect
Steve
 

Offline sebastos08

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #89 on: December 14, 2017, 07:30:17 am »
Hi all,
depending on this review, I decided to buy this item.
I currently own a oscillo, signal generator, DC power supply, dmm.. All in the brand Rigol.

I am globally very satisfied with their products, despite some software bug.
I must say that Dave's reviews weighed a lot in my decisions.

 and especially thanks to Dave's for his "riglol" utility ... about this, is Dave considering completing his great utility to crack access to the options ..?
 

Offline TT_ZX

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #90 on: December 14, 2017, 10:48:17 am »
Where can I find those beefy red and black cables (tagged I partially see BK precision) shown in minute: 28:30?
Any help would be very appreciated.
And thanks all.
My respect
Steve

Are these what you are looking for?
https://www.tequipment.net/BK/TLPWR1/Misc-Test-Leads/
 

Offline Houseman

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #91 on: December 16, 2017, 08:25:12 pm »
Yep!!!
They Are!
I could not find them on the net even searching for BK, the initials I was lurking from the video.. ;D ;D ;D
Thanks alot, Pal.

Regards
 

Offline Smokey

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #92 on: December 19, 2017, 02:42:54 pm »
ppppplease don't spend $75 USD on basic power hookup cables with fork terminals on the ends....  That would make me cry inside. 
If you have to... absolutely have to... I know some other cables that should be right up your alley....


http://www.audiolab.com/audioquest-diamond-hdmi-digital-audio-video-cable-with-ethernet/?utm_medium=googleshopping&utm_source=bc&attributes=eyIxMTM4MiI6Ijk3NTYifQ%3D%3D&gclid=EAIaIQobChMI0JqM3ZOV2AIVBrjACh2ZrA1-EAQYAiABEgIHffD_BwE
 

Offline Mr. Scram

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #93 on: December 19, 2017, 02:45:31 pm »
60A HMDI cables would actually be pretty cool. Useless, yet cool.
 

Offline Decoman

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #94 on: December 19, 2017, 04:23:46 pm »
So in the video there can be seen a Rigol motto printed on the board inside the unit saying "Innovation or nothing". This reminds me of this technologist that showed up to testify in US congress re. internet/security in a hearing not too long ago, but as I remember it seemed to me like something deceptive when the conversation revolved around this nonsensical topic simply named "innovation". There was no explanation given as to what "innovation" would mean, and this more or less well known technologist in this regard ended up parroting the expressed sentiment of a public official on the other side of the panel in that congress hearing, both simply advocated so called "innovation" without explaining what that meant. As I remember it, none of the two at the hearing even bothered to discuss or elaborate on if the meaning of 'innovation' then could perchance come to mean less charming things like developing surveillance software or for espionage, or other similar types of products, and knowing how like businesses keep making new versions of a product to replace old ones for the purpose of selling something perceived as "new" onto a market, I can't help but think that "innovation" is a concept with unclear meaning at best.
« Last Edit: December 19, 2017, 04:45:30 pm by Decoman »
 

Offline sstepane

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #95 on: December 26, 2017, 06:42:39 am »
Hi,

Is any Dl3021 owner in here? I would like to ask what are update refresh options available for monitoring the current, for example?
Can't seem to find anything about it in manual. From video it looks like 1 update/sec, but that's quite slow. Are there any in-device or remote software options on that?
Thanks in advance!
 

Offline policeman0077

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #96 on: June 22, 2018, 03:28:13 am »
Any one knows whats the sampling rate when you use record function?
 

Offline Wolfgang

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Re: EEVblog #1023 - Rigol DL3021 Electronic Load Teardown
« Reply #97 on: June 30, 2018, 09:17:16 pm »
Hi,

after the appropriate cooloff period of almost a year RIGOL seems to have fixed some issues found out by Dave. I tested one now for a week and it operformed without any quirks, so I bought a 200W A version and I like it so far.

The A version is a bit expensive but you can negotiate a bit so its OK in the end.

Best regards
   Wolfgang
 


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