User manual

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.
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 and keys to select the numeric
position. Then use the and keys to select the desired value. Be sure to press
ENTER after changing the reference voltage.
NOTES 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= 20 log
V
IN
V
REF
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2000-900 (J - Aug 2010) BOOK.fm Page 33 Wednesday, October 12, 2011 12:29 PM