The Rigol DM3058 has an option called "Filter" for DC voltage measurement. It can be set to on or off. I'm measuring a DC signal of order +/-30mV with >1MOhm source impedance and significant AC noise superimposed. The filter seems to help the meter get reasonable DC readings; without it, the meter is very inaccurate. The downside is that enabling the filter results in a very slow response time to steps in the signal, like >5s. I plan to try some external filter caps to cut down on the AC noise, so that I can get by without enabling the DM3058 filter.
Does anyone have any information on what the DM3058 filter does and how it works? The manual mentions something about improving the DC voltage accuracy when AC components are present, but it doesn't go into any detail.
Also, there was a thread on this forum in 2015 discussing RFI being emitted from a DM3058 inputs. Has anyone else experienced that?