Keysight U1281A Guide De L'utilisateur page 61

Making Measurements 2
Using the LPF (Low Pass Filter) Function for AC+DC measurements
Your multimeter is equipped with an AC LPF to help reduce electronic noise when
measuring a mixed signal.
1 Enable the LPF (refer to "Enabling the AC path filter (for U1282A only)" on page 140).
2 Rotate the multimeter's rotary switch to
.
V
3 Your multimeter continues measuring in the AC+DC mode, but now the signal diverts
through a filter that blocks unwanted voltages above 440 Hz.
Figure 2-10 AC+DC voltage (with LPF) display
Keysight U1281A/U1282A User's Guide 61