Section 5
:
Relative, Math, and dB
Series 3700 System Switch/Multimeter Reference Manual
5-8
Document Number: 3700S-901-01 Rev. A / August 2007
REF
IN
V
V
20log
dB
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, 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
Selection of UNITS (V or db) can be made 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 wheel to scroll to the "UNITS" menu item. Press the wheel (or the
ENTER
key) to
select.
4. Select units: V for voltage, dB for decibels.
5. Press the wheel (or the
ENTER
key) to set.
6. Press the
EXIT
key to close the attribute menu.
dB Scanning
Each channel in a scan may be configured to use dB. Create a configuration that has the dB
enabled for units for the desired function by using the dmm.configure.set command. Once the
configuration exists, use the dmm.setconfig command to connect the configuration to the
desired channels. Now the channels can be added to scanning (see scan.create and scan.add
commands). To remotely control the units for AC and DC volts, use the dmm.units command.