Keysight U1251B Guia Del Usuario página 55

Measuring AC and DC Signals (U1252B only)
For better accuracy when measuring the DC offset of an AC voltage, measure the AC
voltage first. Note the AC voltage range, then manually select a DC voltage range
equal to or higher than the AC range. This procedure improves the accuracy of the DC
measurement by ensuring that the input protection circuits are not activated.
Keysight U1251B and U1252B User's and Service Guide
Making Measurements 2
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