Rigol DP832A noise levels on output

[Terabyte2007]

First off, this is not a properly controlled noise level test but one I have used to make a general determination as to noise on the DC output on various PS units. I have found that the Rigol DP832A seems to have a bit more background noise on the outputs than other cheaper multi-channel PS units such as the Mastech HY3005F. I used my Agilent 34401A and BenchVue to log a controlled warm-up and run-time period of approximately 34 minutes each from a cold start to full operating temperature. Each power supply used the same cable (Low loss, direct connect banana jacks) to the Agilent and on the same power circuit. I also let the Agilent warm up for an hour prior to the test. The room temperature did not vary more that 1-2 degree over the entire test, Test leads were connected and placed in the exact location to where the PS units were placed. No other gear was operating at this time. Both PS units were setup to around 9.01 volts DC with just the high impedance load of the Agilent.

My preliminary results and repeated tests showed the Rigol DP832A to have a higher noise rail than the cheaper models such as the MasTech and Korad. Keep in mind that this was with no load. What surprised me was the difference in delta between the Rigol DP832A and the MasTech HY3005F.

The Rigol had a min. of 9.00316 and a max. of 9.00539 with a avg. of 9.00482 and a delta of 2.15840 mVdc.

The MasTech had a min. of 9.03310 and a max. of 9.03320 with a avg. of 9.03315 and a delta of 99.8000 uVdc.

I was able to repeat this test several times with very similar results. Has anyone noticed that the Rigol DP832A seems to be a bit noisier than some cheaper units like the MasTech HY3005F? Is there anything I can do to improve this test short of building the proper testing environment?

Attached are the logs.

The Rigol was 9.00568 and the MasTech was 9.03865.

There appears to be slightly over 1.1 mVdc greater noise on the Rigol than the MasTech which was surprising to me to say the least. I also want to add that the Rigol had a better flat DC output once warmed up which the MasTech did continue to slowly rise a bit more.