Rigol DP832 still has voltage even when output is disabled

[Gibson486]

I just got this in. Is this normal? When I shut the output off on channel 1, I get a reading of 9mV on my multi meter. Only seems to happen on that channel.  Is this a known issue?

[Teuobk]

Yup, pretty normal. Turning a channel "off" sets the voltage to roughly zero rather than floating the output jacks.

On mine, channel 2 was putting out about -8 mV while "off" until I wasted half a day calibrating it, after which I eventually got it to be about +4 mV when "off". More details on the DP832 thread.

[Mr. Scram]

The well known Korad supplies show the same behaviour, so it seems it's par for the course.

[mcinque]

The AIM TTi PL303 still the same -9mV.
It's not an a thing of Rigol or Korad... well, it's not even an issue.
I measured ~10uAmp current, it's nothing, it's most probably dued to the leakage of the output transistor

[Helix70]

With what load attached? Just the multimeter? You will get more than 9mv when the cat rubs your leg, but not into a real load.

[mcinque]

Just the multimeter shunt. Around 10uA from + to - and a little more from + to earth gnd.

[Teuobk]

I found that my DP832 will source about 20 mA to a precision 10 mOhm shunt through a set of standard test leads, as measured across the shunt. That's with 3.3 mV potential observed across the terminals (down slightly from the 4.0 mV I saw the last time I checked). The limiting factor in this case seems to be the resistance of the leads themselves, which are on the order of 0.17 Ohm total.

I also checked the DP832's behavior using a Keithley 2450 SourceMeter connected directly to the DP832's terminals via a 4-wire setup. In that test, with the channel nominally off, I found the DP832 would source 3.0 mV @ 10 mA, 2.9 mV @ 25 mA, and 2.8 mV @ 99 mA -- but I suspect the 0.2 mV spread was actually due to the voltage drop in the DP832 terminals themselves at the higher currents. The current limit set on the DP832 channel under test didn't appear to have any effect while the channel was nominally off.

(And yes, I recognize that the second test's numbers aren't completely consistent with the first test's numbers. Not sure why.)

[Gibson486]

Oh well...I have always used >>$1k power supplies. I guess this is just a trade off of going << $500 (limited EE budget ). Other than the extremely laggy dial, it is still a pretty good supply, though.

[techydude]

I just upgraded my DP832 to 00.01.14.00.03, and started doing a manual calibration.  Once it got to a step (in the many steps of manual cal) where it outputs more than what my previous/current OVP setting was (16.8V), it flicks the channel off with the OVP modal-warning.

So I curse the firmware Dogs, save my cals, back out to normal operation, set OVP to max (33.0V) and disable it for good measure.

Now every time I turn off CH1 the modal-warning comes up to say OV-protection's disabled the channel

Indeed, sticking the DMM over it, it's up at the channel's max, 33.x V, bouncing off & on & off & on.

If I stick a light load on the output (circa: hundreds of ohms) it'll settle down to some intermediary V (e.g. 10.x V with a 220ohm load).

Rebooting changes nothing.

It would seem it's not fully disabling its output, and the built-in OV-protection (not the user-settable one) is naturally triggering.

Any ideas?