2-16
IM 701310-01E
2.5 Acquisition Conditions
Acquisition Mode ►For the procedure, see section 7.1
When storing sampled data in the acquisition memory (see “Signal Flow” in section
2.1), it is possible to perform processing on data and display waveforms based on the
processed data. The following three types of data processing are available.
Normal Mode
In this mode, sampled data is stored in the acquisition memory without special
processing.
Envelope Mode
In normal mode or averaging mode, the sample rate (the number of times data is
acquired per second in the acquisition memory) drops if T/div is increased (see Appendix
1). However, in envelope mode, the maximum and minimum values are determined from
the data sampled at 2.5 GS/s at time interval one half that of the sampling period (inverse
of the sample rate) of normal mode regardless of the interleave mode setting (ON or
OFF). The maximum and minimum values are stored as pairs in the acquisition memory.
Envelope mode is useful when you want to avoid aliasing (see next page), since the
sample rate remains high irrespective of the time axis setting. It is also useful when you
want to detect glitches (narrow pulse signals) or display an envelope of a modulating
signal.
Envelope curve
Averaging Mode
In the averaging mode, signals are acquired repeatedly to obtain the average of sampled
data at the same time point (the same time in relation to the trigger point). The DL9000
takes the exponential or simple average of the sampled data and writes the results to the
acquisition memory. The averaged data is then used to generate the display. When the
trigger mode is auto mode, auto level mode, or normal mode then exponential averaging
is used, and in the single mode, simple averaging. This mode is useful such as when
eliminating random noise superimposed on the signal.
For exponential averaging, you set the attenuation constant. For simple averaging, you
set the sampling data acquisition count.
An = {(N – 1)A
n–1
+ X
n
}
1
N
Exponential averaging
(When trigger mode is set to Auto,
Auto Level, or Normal)
A
N
=
N
Simple average
(When trigger mode is set to Single or
N Single)
N
n=1
Σ X
n
An:
Xn:
N:
n
th
averaged value
n
th
measured value
Attenuation constant (2 to 1024, 2
n
steps)
Xn:
N:
n
th
measured value
Acquisition count (2 to 65536 2
n
steps)
