Model 2750 Multimeter/Switch System User’s Manual Rel, Math, Ratio, Channel Average, dB 5-21
dB
Expressing DC or AC voltage in dB makes it possible to compress a large range of mea-
surements into a much smaller scope. The relationship between dB and voltage is defined
by the following equation:
where: V
IN
is the DC or AC input signal.
V
REF
is the 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 V
IN
/ V
REF
.
The largest negative value of dB is -160dB. This will accommodate a ratio of
V
IN
= 1µV and V
REF
= 1000V.
dB configuration
Remote programming must be used to configure the Model 2750 for dB measurements. It
cannot be configured from the front panel.
Scanning
Typically a scan using dB is configured and run using remote programming. However,
once dB is selected using remote programming, a simple dB scan can be configured and
run from the front panel. When the simple scan is configured, it will use the dB measure-
ment setup for each channel in the scan. Details on configuring and running a scan are pro-
vided in Section 7.
NOTE See Section 7 to configure and run a scan.
Remote programming — dB
dB commands
The dB commands are listed in Table 5-4. Details on these commands follow the table.
NOTE Queries are not included in Table 5-4. All the dB commands are provided in
Table 15-10.
dB 20log
V
IN
V
REF
-------------
=
2750-900-01.book Page 21 Wednesday, August 3, 2011 7:56 AM
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