Keysight Technologies 3458A Guide D'utilisation page 188

4 Making Measurements
Using the second equation with the same reading rate and DEGREE produces:
RMS
The RMS math operation can be used to compute the combined RMS value of the
AC and DC components of digitized (using the DCV, DSAC, or DSDC command)
low frequency signals.
For repetitive AC signals of 1 Hz or greater, the synchronous AC measurement
NOTE
method can be used instead of the RMS math operation. If the AC signal is 10 Hz
or greater, the analog AC method can be used. If the signal is 20 Hz or greater,
the random method can be used. You can also determine the RMS value of the
AC component of sinewaves by digitizing (using the DCV, DSAC, or DSDC
command) and enabling the STATS math operation. After a number of readings,
the result in the SDEV register is the RMS value of the AC component of the
input signal.
The RMS math operation takes the square root of the preceding FILTER operation
with the reading and the previous result first squared. The RMS math equation is:
188
≈
t (1/200) × 20 = 0.1 seconds
PreviousResult
Result = - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
DEGREE
Where:
Previous Result is initially set to the value of the first reading and thereafter is
set to the result of this FILTER operation.
Reading is the latest reading taken.
DEGREE selects the step response of the filter.
2
@ DEGREE 1
( )
–
2
Reading
+ - - - - - - - - - - - - - - - - - - -
DEGREE
Keysight 3458A User's Guide