This situation typically arises when changing the voltage unit setting, such as switching to dBm. The dBm unit is only valid for a 50 Ω output impedance, so if you select dBm while the output impedance is set to High Impedance, the system will automatically revert the impedance back to 50 Ω to ensure accurate voltage and power calculations.

The DAC output passes through an analog amplification circuit, and different signal amplitudes will produce different results. At the front end, the analog output is calculated with 12-bit resolution, while the digital signal processed at the back end has a 16-bit resolution. Achieving a 1 mV step adjustment at a 5 V range is not feasible, and attempting it at 20 V exceeds the actual DC output capability. To achieve 1 mV resolution, you can try using lower voltage ranges, such as 20 mV or 100 mV.

55011, 55012, 55013, 55014, 55015, 55022

The internal resistance of the signal source is 50 Ω.