SEFRAM 7352B Manuel D'utilisation page 37

Make dB measurement
The meter is capable of displaying voltage as a dB value, either
relative to 1 milliwatt (dBm), a reference voltage of 1 volt (dB).
A dBm measurement must use a reference impedance (600Ω)
to calculate a dB value based on 1 milliwatt. A dB measurement
uses a 1 volt reference voltage to compare the present
measurement against. Define as below :
To use dB or dBm function, turn the rotary switch to ACV or
ACmV position. Then move the blink cursor of menu to dB or
dBm position, and press the ENTER button to enter function.
Press the CANCEL button to exit function.
Measuring Voltage in LoZ Mode
 CAUTION

Do not use the LoZ mode to measure voltages in circuits
that could be damaged by this mode's low impedance.
To eliminate ghost voltages, the meter's LoZ mode presents a
low impedance across the leads to obtain a more accurate
measurement. The ranges of measuring LoZ voltage are 400V
and 1000V. In this mode, meter will automatic measure input
signal which is AC or DC and determine range.
To use the LoZ mode, turn the rotary switch to LoZ position.
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