In the SCPI command set mode, the following commands will get you there: :SENSE:FUNC 'VOLT:AC' :VOLT:AC:UNIT DB :SENSE:VOLT:AC:DET:BAND 300 :SENSE:VOLT:AC:DB:REF 5 This will set the unit to ACV, db and reference of 5. If the unit is set to TSP, then use these commands: dmm.measure.func = dmm.FUNC_AC_VOLTAGE dmm.measure.unit = dmm.UNIT_DBM dmm.measure.detectorbandwidth = dmm.DETECTBW_300HZ dmm.measure.dbreference 5