Found Bug in Rigols DP832

[rbola35618]

Hi EEblogger,

I think I found a bug in the DP832. I have three of the DP832 that have the same problem.   The problem appears in channel 1.  With no load, if you set the voltage on channel 1 to 1 volts and then try to set the current to 9mA or less, the current display shows that 43ma is being delivered.  I can then use the rotary dial to slowly increase the current limit from 1ma and finally at 10mA, the current display then does back to zero amps

 If you do the same to channel 2, no problem. You can set the current limit all the way down to 1 mA in channel 2. However channel 1, the current limit start acting up below 10mA. 

I also checked channel 3, it works all the way down to 1mA. So channel 3 is working properly.

I have the Hi resolution option. I think it may be a firmware problem. Will be calling Rigol to let them know.

Anybody that has the hi res option check their PS.

Robert

[Monsterhero]

Hey,

i just got my DP832A today.
Now I read your post and thought: Hey I should test this.

Result:

Same problem with the A-Model. If I set the current under 10 mA the device reads 38mA back.
This happens with every set voltage.
Also only on CH 1


Daniel

[mcinque]

Same behaviour on mine with firmware version 00.01.04, let us know what's the reply from Rigol, they should provide an update.

[Sienna]

I wonder if this is also a bug or a feature:

When set to track mode, the other channel does not track current limits, only voltages. 
(Rev 3 PCB, FW 00.01.06)

[mcinque]

I wonder if this is also a bug or a feature:

Imo it's a feature.

[JimmyMz]

The problem appears with channel 1 of the Rigol DP832. If you set the voltage on channel one to equal 1V, and then set the current to equal 9mA or less (with no load attached to the power supply), the current display indicates that 43ma is being delivered by the DP932 power supply.  In my testing, I then used the Rigol DP832's rotary dial to slowly increase the current from 1mA to 10mA, the current display then does back to zero amps.

^^What does the boldened section actually mean? Are you saying at 10mA the Rigol DP832 power supply changes its measurement reading from 10mA to indicate 0A is being delivered?

[TooOldForThis]

the current display then does back to zero amps.

^^What does the boldened section actually mean? Are you saying at 10mA the Rigol DP832 power supply changes its measurement reading from 10mA to indicate 0A is being delivered?
[/quote]

Early versions of the DP832 firmware had a bug where if you set the current LIMIT below 11mA,  the DP832 would falsely claim that it was sourcing 43mA when no load was attached.   When you increased the current limit to 11mA or more, the supply began to show the correct actual current of 0.   Rigol fixed this feature in SW rev 1.06. 

[JimmyMz]

the current display then does back to zero amps.

^^What does the boldened section actually mean? Are you saying at 10mA the Rigol DP832 power supply changes its measurement reading from 10mA to indicate 0A is being delivered?

Early versions of the DP832 firmware had a bug where if you set the current LIMIT below 11mA,  the DP832 would falsely claim that it was sourcing 43mA when no load was attached.   When you increased the current limit to 11mA or more, the supply began to show the correct actual current of 0.   Rigol fixed this feature in SW rev 1.06.
[/quote]
Oh, okay! Thank you for answering my question. I wanted to fully understand what the problem truly was, and I now I can say, I fully understand. Thank you 

[AndersAnd]

Hi EEblogger,

I think I found a bug in the DP832. I have three of the DP832 that have the same problem.   The problem appears in channel 1.  With no load, if you set the voltage on channel 1 to 1 volts and then try to set the current to 9mA or less, the current display shows that 43ma is being delivered.  I can then use the rotary dial to slowly increase the current limit from 1ma and finally at 10mA, the current display then does back to zero amps

 If you do the same to channel 2, no problem. You can set the current limit all the way down to 1 mA in channel 2. However channel 1, the current limit start acting up below 10mA. 

I also checked channel 3, it works all the way down to 1mA. So channel 3 is working properly.

I have the Hi resolution option. I think it may be a firmware problem. Will be calling Rigol to let them know.

Anybody that has the hi res option check their PS.

Robert

Dave talks about this bug in this video:
EEVblog #549 – Rigol DP832 Lab Power Supply Followup
http://www.eevblog.com/2013/11/19/eevblog-549-rigol-dp832-lab-power-supply-followup/

The bug has been fixed in the latest firmware as Dave demonstrates.

[glano]

Well, I'm pretty excited to get my DP832 and DS1104Z-S.  Need to get those write-offs in before the end of the calendar year!

Anyway, I was semi-bummed to see my DUT briefly get some power when switching on the DP832.  Here's a scope of channel 1 when turning on the DP832, I'm not sure how much current it's sourcing and maybe it's bad practice to have the DUT connected when powering on the power supply but what's the point of being able to turn on/off the channels if you have to disconnect your load?

[verbatone]

Hi...first post...I know, pretty old thread, but well, I feel like it's applicable.

I just bought a DP832 this week, seems like everything is pretty much how it should be, except, well, I think I have something related to this bug.  If I have no load, i see the current meter showing .04A, only on CH1.  Strangely, this doesn't seem to have anything to do with the current limit that others had mentioned from this thread.  I can set the current limit at 1A and still see the issue.  The power is always V*I as well, so for 10V output, I see 40mW of power, for 20V output, I see 80mW.   Also funny, if I add a small load, the issue disappears.  With small enough current draw, I can get the current and power to show 0A and 0W.

I upgraded FW to 1.14 last night, I didn't expect a fix, and I didn't get one.  Again, this is a brand new unit.  Is there something that's quite possibly wrong with my unit, or is this a new version of the same FW bug?  Seems strange that I'm the only one that's seen this of recent.

[verbatone]

Rigol got back to me and said the unit needs to be recalibrated...they recommend exchanging the unit for a new one.  Oh well! Back it goes, luckily I have my trusty old GW Instek in the meantime.