Agilent Technologies InfiniiVision 5000 Series User Manual page 208

6
Measurements and Math Functions
208
Peak-Peak
The peak-to-peak value is the difference between Maximum and Minimum values. The Y
cursors show the values being measured.
Ratio
The Ratio measurement displays the ratio of the AC RMS voltages of two sources,
expressed in dB. Press the Settings softkey to select the source channels for the
measurement.
RMS
RMS (DC) is the root-mean-square value of the waveform.
n

x
2
i
=
i 1
--------------- -
RMS (dc) =
n
Which samples are measured depends on the Interval setting:
• N Cycles — the RMS (DC) value is measured on an integral number of periods of the
displayed signal. If less than three edges are present, the measurement shows "No
edges".
• Full Screen — the RMS (DC) value is measured on all displayed data points.
• Auto — the measurement attempts to compute a value using the N Cycles interval. If
less than three edges are present, the measurement is computed using the
Full Screen interval.
The X cursors show what interval of the waveform is being measured.
Std Deviation
The Std Deviation measurement shows the standard deviation of the displayed voltage
values. It is an RMS measurement across the full screen with the DC component
removed. It is useful, for example, for measuring power supply noise.
The standard deviation of a measurement is the amount that a measurement varies from
the mean value. The Mean value of a measurement is the statistical average of the
measurement.
where x = value at ith point being measured
i
n = number of points in measurement interval
InfiniiVision Oscilloscopes User's Guide