Author Topic: Rigol DL3021 current offset  (Read 416 times)

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Offline sebastos08

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Rigol DL3021 current offset
« on: December 22, 2017, 06:22:42 PM »
Hi all,

I recently bought a DL3021 Rigol DC electronic load, for tests in low consumption.
I also purchased the HIRES-DL3 option to access more accurate display "High Measurement Resolution Option"

I have several devices of the brand, and I was confident in this new purchase

After a few tries, I immediately noticed something that seemed to me abnormal.
In static CC mode, for an I of 10mA of load, my power supply and my dmm displays 20mA of real current. (see photo2)
We are here far from the 0.05% + 0.05% FS specification.
In my case, we should not exceed 0.010x0.05% + 0.05% x4A = 2mA error.

I wanted to investigate the problem by checking that the voltage raised in the DL3021 has no influence in this offset, but in "CC" mode, the voltage has no influence on the regulation of the current I. ( tests done with EXT sense on)

I noticed that the DL3021, also sinked 10mA when it was not loading "OFF mode". (see photo1 on my power supply and my dmm)

I do not know if there is a relation between this two measurements states and I asked the question to Rigol and I do not have a response from them yet.

Is my concern specific to my machine, is it someone who owns this device could tell me if he is experiencing the same problem as me. ?

I am for the first time disappointed with the brand and I hope to find a possible way of solution. Otherwise I think I will return the device and turn to another brand ..

Case to follow......
« Last Edit: December 22, 2017, 08:47:44 PM by sebastos08 »

Offline TurboTom

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Re: Rigol DL3021 current offset
« Reply #1 on: December 23, 2017, 06:07:48 AM »
Yes it's doing these kind of things...  Be sure to check the last two pages of this thread:

In it's current condition, at least the specimen of the DL3021 I tested was utterly useless for low-current jobs. Check the waveform of the current, it's far from DC. My recommendation would be to return it and get either a Maynuo or an Applent (you even pay a little less for those if you import them from China directly, but they aren't perfect either...though much better than the Rigol).

I think as long as these instruments use a single shunt resistor for the full current range, poor performance at the low current end is no surprise at all. Especially Rigol uses a very low shunt (0.5mOhm -- Applent and probably also Maynuo have a total shunt resistance in the ballpark of 15mOhm).

Good luck,

Offline sebastos08

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Re: Rigol DL3021 current offset
« Reply #2 on: December 24, 2017, 12:25:41 AM »
Thanks a lot Thomas for this reply.

i didn't see the interresting topic that you linked in the previous post before.
it's really very interesting all the analyzes and measurements that you have done.

but I don't understand that when the machine is OFF, the shunt resistor must not sink any current.
why did I have 10mA on my machine. it seems to me huge and completly out of Rigol specs .. you spoke by your side of 3 to 5mA, is that it?

I especially suspect that there were no calibrations that were done on my machine.
« Last Edit: December 24, 2017, 12:27:28 AM by sebastos08 »

Offline sebastos08

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Re: Rigol DL3021 current offset
« Reply #3 on: December 24, 2017, 04:13:59 AM »
When testing small currents, for example, currents less than 10 mA, my DL3021A does not apply the correct current until it reaches 8 or 9mA, then when dialing back to 0mA it seems to work until you reach 0mA then the trouble starts over.
For example, setting the load to 0mA applying a source voltage 3.3V shows:

current setting    read value  (manually increasing by 1mA)
0.000A               0.0021A
0.001A               0.0022A
0.002A               0.0023A
0.003A               0.0023A
0.004A               0.0023A
0.005A               0.0024A
0.006A               0.0024A
0.007A               0.0025A
0.008A               0.0025A
0.009A               0.0095A  <- trigger point
once this point is reached it will work when dialing backwards until the error message at 0mA is shown then the same behavior repeats. 

The general offset of 2mA is already bad, but this hysteresis behavior is really annoying.  Range is set to 4A but it does not make a difference if set to 40A.  Slew rate changes make also no difference.
Anybody got the same erroneous behavior?

interesting feedback too.

i haven't made this range tests between 0-10mA. i'll do it next week.

As Thomas said above or in another subject, I think this DL3021 is not made for its low current values.  >:( >:( >:( :( :(

I'm moving more and more towards the idea of an exchange with a MAYNUO M9711 or 9712

This product don't seems to be ready for the public.

it's a shame because I like its screen and the adjustment interface it offers
« Last Edit: December 24, 2017, 04:16:09 AM by sebastos08 »

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