User manual

Section 6: Relative, Math, and dB Series 3700 System Switch/Multimeter Reference Manual
6-10 3700S-901-01 Rev. C / July 2008
dB commands
Expressing DC or AC voltage in dB makes it possible to compress a large range
of measurements into a much smaller scope. The relationship between dB and
voltage is defined by the following equation:
Where:
V
IN
: DC or AC input signal.
V
REF
: Specified voltage reference level.
The instrument will read 0dB when the reference voltage level is applied to the
input. If a relative value is in effect when dB is selected, the value is converted to
dB, and then REL is applied to dB. If REL is applied after dB has been selected,
dB has REL applied to it.
NOTE The dB calculation takes the absolute value of the ratio VIN / VREF.
The largest negative value of dB is -160dB. This will accommodate a
ratio of VIN = 1µV and VREF = 1000V.
dB configuration
You can select UNITS (V or dB) from the front panel.
To select UNITS from the front panel, while in DCV or ACV:
1. Press the CONFIG key.
2. Press the DMM key.
3. Turn the navigation wheel to scroll to the UNITS menu item.
4. Press the navigation wheel (or the ENTER key) to select.
5. Select units: V for voltage or dB for decibels.
6. Press the navigation wheel (or the ENTER key) to set.
7. Press the EXIT key to close the attribute menu.