Db Calculation - Keithley 2000 User Manual

dB calculation

Expressing DC or AC voltage in dB makes it possible to compress a large range of measure-
ments into a much smaller scope. The relationship between dB and voltage is defined by the
following equation:
where: V
IN
V
REF
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.
Configuration
To set the reference voltage, perform the following steps:
1. After selecting dB, the present reference voltage level is displayed:
REF: +0.000000
2. To change the reference level, use the
Then use the
changing the reference voltage.
NOTES The dB calculation takes the absolute value of the ratio V
The largest negative value of dB is -160dB. This will accommodate a ratio of V
1µV and V
dB= 20 log ----------------- -
V
is the DC or AC input signal.
is the specified voltage reference level.
and keys to select the desired value. Be sure to press ENTER after
= 1000V.
REF
Basic Measurements
V
IN
REF
and keys to select the numeric position.
2-33
/ V
IN REF
=
IN