User Manual

96 ISSUED: June 2013 923133 Rev A
USING PARAMETERS WITH TRENDS AND XY PLOTS
X-axis Y-axis
t@pit Dp2c
edgsh
pbase
pmax
pmin
ptop
pwid
pwid pbase
pmax
pmin
ptop
ptop pmax
pbase pmin
We saw in th
e t@pit parameter description how the ORM parameters have
certain unique characteristics that make particular measurements useful
when trended together with XY plots. And how the t@pit parameter is
essential to those measurements. Plots that can be generated on single
acquisitions include those listed in the table at left.
The reason that these plots are considered useful on single acquisitions is
because the parameters are guaranteed to be configurable in a manner
that meets the following criteria:
• Each parameter is capable of providing multiple values per acquisitio
n.
•
Each parameter pair is configurable in a manner that guarantees the
same number of events per wavefo
rm.
•
Each parameter pair must be configurable in a manne
r that
guarantee
s a one-to-one correspondence between paramete
r
cal
culatio
n values.
Example and Step-by-Step Instructions
Here is an example typifying the use of XY plots without the t@pit parameter. A complete
example using t@pit has been provided in the section dedicated to this parameter description.
Consider a situation in which it is desirable to find the relationship of the pit top value to the pit
width in an optical recognition data waveform:
The scope is set up to acquire this waveform by assigning Channel 1 to the data signal at a
time/div of 0.2 ms. This signal will contain approximately 1800 pits/spaces. The ideal threshold
has been determined by the pmidl parameter as 1.9 mV.
The ptop custom parameter is assigned to P1, and the pwid parameter is assigned to P2. Use
configuration tracking to configure both parameters in the following manner:
hysteresis = 0.5 divisions
threshold = 1.9 mV
polarity = Pos
range of n
low n = 3
high n = 11
period = 231.5 ns
In math setup, F1 is defined as the trend of the ptop parameter and F2 as the trend of the pwid
parameter. Because we are expecting 1800 pits/spaces, make sure that for each math setup the
trends are set to use up to 20,000 values, the maximum amount.
Note: If configuration tracking is used on the ptop parameter, the pwid parameter must be visited in order to set the
polarity to positive because ptop inherently implies positive polarity pits.