Author Topic: Digital load recommendations  (Read 1469 times)

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Offline forrestc

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Digital load recommendations
« on: December 05, 2017, 01:26:20 am »
My rebadged Array 3711A on the bench is starting to act a bit wierd, in particular the voltage reading bounces all over the place, at least when cold.   Plus, the large capacitance on the input drives me nuts, along with the reverse polarity protection in the form of what seems like a diode across the input (which is ok, just annoying when you get a connection backwards).  Been wanting a new one for a while, and with the new weirdness it's probably time.

For those of you with electronic loads, what do you have, and what do you find nice and what do you find annoying?
 

Offline DuPe

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Re: Digital load recommendations
« Reply #1 on: December 05, 2017, 06:46:05 pm »
Hi,
I own a Maynuo M9811 and can recommend it.
Only flaw I found so far is: They are not very reliable with their factory calibration.
Mine was a little off at voltage calib., but recalibrating is no big deal.
See there
https://www.eevblog.com/forum/testgear/it8512(a)-or-the-m9812/msg934851/#msg934851
cheers
Peter
Edit: Comes with a usable piece of Software, but you need an isolated usb to serial converter.
They are offering it together with the load for a reasonable money
« Last Edit: December 05, 2017, 06:56:45 pm by DuPe »
 

Online nctnico

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Re: Digital load recommendations
« Reply #2 on: December 05, 2017, 08:21:04 pm »
AFAIK there are all based on -more or less- the same design. They will all have the same reverse polarity protection due to the inherent reverse diode in a MOSFET. Also the capacitance is probably there to get good loop stability. It takes a much better design to circumvent that.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline rx8pilot

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Re: Digital load recommendations
« Reply #3 on: December 05, 2017, 08:54:13 pm »
With some patience, look at Chroma on the used market. I have been using them for a couple of years in a multi-channel config. Pretty good bang for the buck. Certainty had my Array units looking for a trash can real fast.

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Offline forrestc

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Re: Digital load recommendations
« Reply #4 on: December 05, 2017, 11:02:40 pm »
AFAIK there are all based on -more or less- the same design. They will all have the same reverse polarity protection due to the inherent reverse diode in a MOSFET. Also the capacitance is probably there to get good loop stability. It takes a much better design to circumvent that.

The reverse diode in the mosfet I hadn't thought about.... That makes sense,

In relation to the capacitance, I totally get that, but we're talking about 150uF.  I've blown up more than one object just due to the inrush of charging this capacitor.   If you have a load set to 'off'  you really don't expect it to take an infinite amount of amps intitially.  Well, you do, once you learn this, doesn't make it any more acceptable.

This large of a capacitor makes it difficult to use it to provide a load for any device which would be sensitive to this, and it is amazing how many things are sensitive to this.   For instance, I was trying to test switching capacity of a 1A reed relay and was welding the reed relay contacts with the load disabled.

 

Offline forrestc

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Re: Digital load recommendations
« Reply #5 on: December 05, 2017, 11:12:26 pm »
With some patience, look at Chroma on the used market. I have been using them for a couple of years in a multi-channel config. Pretty good bang for the buck. Certainty had my Array units looking for a trash can real fast.

Looks like a good mix on ebay, I'll have to keep my eye opened.  Looks like there's some chassis options with a single load which will be better suited for bench use. 

I've been using a HP 6063B in the automated test rack, About the only thing I have to watch for is the 3 volt minimum, I'm guessing there's a diode junction in there somewhere (BJT load perhaps?).   But it's way too big to use on the R&D bench, not to mention the annoying interface - it was obviously designed for GPIB control, not for human control.



 


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