YOKOGAWA DL7440 User Manual

2-16 IM 701450-01E
Envelope Mode
In normal mode and 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 1 GS/s or 800 MS/s at time intervals 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 section 2.2), since the
sample rate is kept high irrespective of the time axis setting. It is also useful when you
want to detect glitches (pulse signals which rise very fast) or display an envelope of a
modulating signal.
Envelope curve
Averaging Mode
Averaging is a process in which waveforms are acquired repeatedly to obtain the
average of waveform data at the same time point (the same time in relation to the trigger
point). The DL7400 takes the exponential or simple average of the waveform data and
writes the results to the acquisition memory. The averaged data is then used to
generate the display. This mode is useful such as when eliminating the random noise
riding on the signal. The attenuation constant of exponential averaging can be set in the
range of 2 to 256 (2
n
steps, where n is a positive integer). The average count of simple
averaging can be set in the range of 2 to 65536 (2
n
steps, where n is a positive integer).
An = {(N–1)A n–1 + X n }
1
N
Exponential averaging (when set to infinite)
A
N =
N
Simple average (when set to 2 to 65536)
N
n = 1
Σ X n
An
Xn
N
: n
th
averaged value
: n
th
measured value
: Attenuation constant (2 to 256, 2
n
steps)
Xn
N
: n
th
measured value
: Average count
(acquisition count, 2
n
steps)
Box Average
The moving average of the data sampled at 1 GS/s or 800 MS/s is determined regardless
of the interleave mode setting (ON/OFF). The resultant data is stored in the acquisition
memory and displayed. Box averaging is useful for eliminating small amounts of noise from
the input signal. It can also remove noise from a single-shot signal.
Time
Time
1
2
32
40
a
41
Input signal
(20 MS/s)
Box averaged data
VoltageVoltage
b
• • • •
72
• • • • •
• • •
2.4 Waveform Acquisition and Display Conditions

YOKOGAWA DL7440 Specifications

General

Brand	YOKOGAWA
Model	DL7440
Category	Test Equipment
Language	English