Voltage Readout Problem with New Rigol DP832 - Page 1
Forum section: electronics / testgear

author: Bronco Leonard
author_rank: Newbie
timestamp: June 14, 2016, 12:00:12 am
content: Hello Everyone,After years away from it, I am getting back into the hobby and started by acquiring some new toys. I just bought myself a new Rigol DP832 power supply through Saelig and it arrived well packaged and shiny as expected. I began experimenting with it and about the first thing I noticed is that under a large current load, the indicated voltage on each of the 30 vdc channels was lower by nearly half volt than what I measure with either of my Fluke multimeters (a brand new 87V and an old 77). At low current loads, all three voltage meters (the PS and the two mm's) agree exactly, but when I increase the current load to about 2.8 amps (using an old 6 ohm, 250 w resistive load), the PS voltage readings are about 0.45 volts lower than the two MM's. This behavior is identical on both PS channels 1 and 2. I used another dummy load to test at about 1.4 amps and the error was still present, albeit smaller, so the voltage error seems to be somewhat proportional to the current load. BTW, I substituted each of the multimeters to measure the current and each agreed very closely with the power supply, so the PS current measurement does not seem to be an issue.It may be that I'm doing something wrong, but if not, then this is a pretty simple thing to be wrong with the power supply, clearly way-out-of-spec behavior. Any thoughts?

author: tautech
author_rank: Super Contributor
timestamp: June 14, 2016, 12:08:49 am
content: Welcome to the forum.There's a thread on these PSU's:https://www.eevblog.com/forum/testgear/rigol-dp832-firmware-updates-and-bug-list/Similar problems are linked in the thread but with all equipment it's a good idea to update FW if your supplier didn't before they dispatched it.

author: Bronco Leonard
author_rank: Newbie
timestamp: June 14, 2016, 12:11:46 am
content: I didn't expect to need to do this with a unit right off the shelf, but I will do the firmware update and report back. Thanks.

author: tautech
author_rank: Super Contributor
timestamp: June 14, 2016, 12:17:24 am
content: Quote from: Bronco Leonard on June 14, 2016, 12:11:46 amDo expect it, most of the large resellers don't have the time or resources to provide decent support at even presale.

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: June 14, 2016, 12:36:48 am
content: The newest firmware for the DP832 is from Apr 24th, 2015. Its full version number is 00.01.14.00.03, which is reported if you check directly on the DP832 as 00.01.14. If it doesn't come with that firmware on it (already over a year old) I would be concerned with it maybe not having all the hardware fixes Rigol have applied over the years. Though I didn't think there would be any of the older hardware models still being sold as new, especially not from someone like Saelig. Whats the calibration date on it?Edit: Not trying to worry you, I very much doubt that would happen from Saelig, just adding more info.

author: Bronco Leonard
author_rank: Newbie
timestamp: June 14, 2016, 05:02:19 am
content: OP here. The paperwork shows a calibration date of 2-26-16 and the reported firmware is 00.01.14, so it seems to be pretty new. I suppose it's possible that there is a newer firmware release that would take care of this problem, but not likely. I sent a tech support request earlier via e-mail and got an automated reply within about an hour with a case number and the name of the tech who is supposed to deal with this. Courtesy of this thread, I'm shifting my tech support question from firmware to specifically dealing with this voltage issue. I'll post results of my tech support journey.How disappointing. I bought what I thought was a decent quality PS and right out of the gate, something's wrong.

author: H.O
author_rank: Frequent Contributor
timestamp: June 14, 2016, 05:21:01 am
content: Are you connecting the DMM right across the output terminals of the powersupply?If you connect the DMM across the load then you have to take into consideration the voltage drop in the wiring between the PSU and the load.Although I have a DP832 I don't know exactly where it measures the voltage (I'm sure it can be found out by looking thru the referenced thread) but I guess it's at the terminals though it might be at some internal point in which case there will be a slight voltage drop across the internal wiring.

author: jitter
author_rank: Frequent Contributor
timestamp: June 14, 2016, 08:14:55 am
content: Quote from: H.O on June 14, 2016, 05:21:01 amPlease reread the OP. It's the PSU that reads 0.45 V lower (@ 2.8 A load) than it actually puts out.

author: H.O
author_rank: Frequent Contributor
timestamp: June 14, 2016, 10:18:41 am
content: Duh..Hadn't had my morning coffee...

author: jitter
author_rank: Frequent Contributor
timestamp: June 14, 2016, 11:24:32 am
content: Quote from: H.O on June 14, 2016, 10:18:41 amI know what you mean...

author: Bronco Leonard
author_rank: Newbie
timestamp: June 16, 2016, 05:01:32 pm
content: Problem solved - I had some unexpected resistance in my so-called "heavy duty" leads adn this created a small but measurable voltage drop. I'm not sure why I saw (or thought I saw) a higher voltage on the multimeters than on the Rigol, but ...Anyway, everything seems to be working well now.I appreciate the help from the forum members who responded, and I look forward to learning a great deal from all of you.I should also mention that I requested customer support from Rigol and they did a very nice job of responding promptly. I was in an e-mail exchange with one of their techs the next day. So far, so good with them.Bronco L.