New DP832A - Odd Behavior - Bad calibration?

[K1JOS]

I just got a new DP832A that shows a calibration sheet by Rigol mid-September 2013.  It has Digital firmware 00.01.06.00.00 and Analog v. 01.01.07.01.01.07 and Boot 01.05.  It does have the shiny aluminum heat sink.

Using a 0.01% precision 1w resistor of 2000 ohms (confirmed 2000.1 ohms on a NIST Agilent 33410A) I found channel 1 to be spot on with a 832A setting of 10.000v and 0.005A my Agilent meter confirmed the CC output was 5.0 ma at 10.000 vdc.  However on channel 2 when set exactly the same the DP832A display shows 0.005A at only 8.765 vdc.  I confirmed with the Agilent meter that the actual current was only 4.375 ma @ 8.750vdc and I have to increase the current to 0.006 to reach 10.000v.  Also Channel 2 when set at 0 vdc and any non-zero current setting (0.001 or higher) the 832A displays the Ch 2 voltage incorrectly as 0.015v not zero.  On the Agilent I confirm the current and voltage are both zero.  On the 832A, the display voltage only goes to 0.000 if the current is set to 0.000.  This behavior is not seen on Ch1 or Ch 3 (using 5v).  Is this a simple calibration error or symptomatic of something more?

thanks
jerry

[K1JOS]

Anyone with any advice.. can I just re-calibrate or do i return it?

tia
jerry

[AlfBaz]

Have a look at the few videos Dave did on this unit. I seem to recall the way they wired channel 2 and the sense resistors was a bit odd that caused issues like this. The latter problem may be related to a firmware bug that's been fixed in a new firmware release

Also do a search on this forum, there's quite a few long threads discussing these problems and others

[RRobot]

However on channel 2 when set exactly the same the DP832A display shows 0.005A at only 8.765 vdc.  I confirmed with the Agilent meter that the actual current was only 4.375 ma @ 8.750vdc and I have to increase the current to 0.006 to reach 10.000v.

If I understand this correctly you had it in cc mode to the last digit and found it to be 1 mA out? The extra resolution does not translate to accuracy, so are there published specs for the DP832A? Both channels may be in spec, even if  channel one performs better.

I just tried this on a regular DP832 with a 3.3 KOhm resistor (unmeasured) and got 0.005 A on channel 1 and 0.006 A on channel 2 at 10V, so obviously not very accurate, but the may be in spec. Perhaps might improve a bit if left on.

As for your other issue, sounds like a firmware bug.

[EDIT], after leaving on for a bit Channel 2 went to 5 mA, still not right but better than before.

[EDIT AGAIN], now its down to 4 mA on channel 2, so perhaps leave it run for a bit.

[K1JOS]

Thanks for the replies, very much appreciated.  I let the supply cook for over an hour before taking measurements.  I am not concerned about the 1 mA resolution or accuracy but when set for 5ma @ 10vdc, with the 1kohm load the supply only reads 8.750vdc (in cc).  This seems way beyond out of spec but in cc mode the difference may only be 1mA.  When you saw the fluctations in mA reading  did you voltage reading on the 828 stay the same?

jerry

[Sparky]

I just got a new DP832A that shows a calibration sheet by Rigol mid-September 2013.  It has Digital firmware 00.01.06.00.00 and Analog v. 01.01.07.01.01.07 and Boot 01.05.  It does have the shiny aluminum heat sink.

Using a 0.01% precision 1w resistor of 2000 ohms (confirmed 2000.1 ohms on a NIST Agilent 33410A) I found channel 1 to be spot on with a 832A setting of 10.000v and 0.005A my Agilent meter confirmed the CC output was 5.0 ma at 10.000 vdc.  However on channel 2 when set exactly the same the DP832A display shows 0.005A at only 8.765 vdc.  I confirmed with the Agilent meter that the actual current was only 4.375 ma @ 8.750vdc and I have to increase the current to 0.006 to reach 10.000v.  Also Channel 2 when set at 0 vdc and any non-zero current setting (0.001 or higher) the 832A displays the Ch 2 voltage incorrectly as 0.015v not zero.  On the Agilent I confirm the current and voltage are both zero.  On the 832A, the display voltage only goes to 0.000 if the current is set to 0.000.  This behavior is not seen on Ch1 or Ch 3 (using 5v).  Is this a simple calibration error or symptomatic of something more?

thanks
jerry

You may be interested in following this thread, where I'm trying to keep track of the firmware revisions and hardware issues. 

Cheers!