User`s guide

Vector Scope
5-513
Scaling the Horizontal Axis for User-Defined Signals
To correctly scale the horizontal axis for user-defined signals, the block needs
to know the spacing of the data in the input. This is specified by the
Increment
per sample in input frame
parameter, I
s
. This parameter represents the
numerical interval between adjacent x-axis points corresponding to the input
data. For example, an input signal sampled at 500 Hz has an increment per
sample of 0.002 second. The actual units of this interval (seconds, meters,
Volts, etc.) are not needed for axis scaling.
When the
Inherit sample increment from input check box is selected, the
block scales the horizontal axis by computing the horizontal interval between
samples in the input frame from the frame period of the input. For example, if
the input frame period is 1, and there are 64 samples per input frame, the
interval between samples is computed to be 1/64. Computing the interval this
way is usually only valid if the following conditions hold:
•The input is a nonoverlapping time-series; the x-axis on the scope represents
time.
•The input’s sample period (1/64 in the above example) is equal to the period
with which the physical signal was originally sampled.
In other cases, the frame rate and frame size do not provide enough
information for the block to correctly scale the horizontal axis, and you should
specify the appropriate value for the
Increment per sample in input frame
parameter. The range of the horizontal axis is [0,M∗I
s
∗S], where M is the
number of samples in each consecutive input frame, and S is the
Horizontal
display span parameter
.
Scaling the Horizontal Axis for Frequency-Domain Signals
In order to correctly scale the horizontal (frequency) axis for frequency-domain
signals, the Vector Scope block needs to know the sample period of the original
time-domain sequence represented by the frequency-domain data. This is
specified by the
Sample time of original time series parameter.
When the
Inherit sample time from input check box is selected, the block
scales the frequency axis by reconstructing the frequency data from the
frame-period of the frequency-domain input. This is valid when the following
conditions hold: