LeCroy Digital Oscilloscopes User manual

Hands-On Guide
to LeCroy
Color
Digital Oscilloscopes
Revision C — April 1998

LeCroy Corporation
700 Chestnut Ridge Road
Chestnut Ridge, NY 10977–6499
Tel: [phone], Fax: [phone]
LeCroy SA
2, rue du Pré-de-la-Fontaine
1217 Meyrin 1/Geneva, Switzerland
Tel: [phone], Fax: [phone]
Internet: www.lecroy.com
Copyright © April 1998, LeCroy. All rights reserved. Information in this publication supersedes all
earlier versions. Specifications subject to change.
LeCroy, ProBus and SMART Trigger are registered trademarks of LeCroy Corporation. Centronics
is a registered trademark of Data Computer Corp. Epson is a registered trademark of Epson
America Inc. I2C is a trademark of Philips. MathCad isa registered trademark of MATHSOFT Inc.
MATLAB is a registered trademark of The MathWorks, Inc. Microsoft, MS and Microsoft Access are
registered trademarks, and Windows and NT trademarks, of Microsoft Corporation. PowerPC is a
registered trademark of IBM Microelectronics. DeskJet, ThinkJet, QuietJet, LaserJet, PaintJet, HP
7470 and HP 7550 are registered trademarks of Hewlett-Packard Company..
Manufactured under
an ISO 9000
Registered
Quality Management
System
Visit www.lecroy.com
to view the certificate.
This electronic product is
subject to disposal and
recycling regulations that
vary by country and
region. Many countries
prohibit the disposal of
waste electronic
equipment in standard
waste receptacles.
For more information
about proper disposal
and recycling of your
LeCroy product, please
visit
www.lecroy.com/recycle.
LCXXX-HG-E Rev C 0498

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A broad overview of the Digital Storage Oscilloscope, zooming
on LeCroy Color DSOs.
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Basic Elements...................................................................1–2
Bandwidth............................................................................1–3
Sample Rate.......................................................................1–4
Memory Length...................................................................1–4
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Acquisition Technique ........................................................1–5
Analog–Digital Conversion.................................................1–6
Number of Channels ..........................................................1–6
Triggering............................................................................1–6
6LJQDO9LHZLQJ............................................................................1–7
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Pulse Parameters...............................................................1–8
Waveform Math..................................................................1–8
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Time Domain ......................................................................1–9
Frequency Domain.............................................................1–9
Statistical Domain...............................................................1–9
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Removable Hard Disk Drive (HDD).................................1–10
Interfaces...........................................................................1–11

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3DUW*HWWLQJ6WDUWHG An illustrated tour of the scope, then ‘hands-on’ for a run
through its basic functions
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,QLWLDOL]DWLRQ.................................................................................2–4
:DYHIRUP$FTXLVLWLRQ .............................................................2–7
TRACE ON/OFF.................................................................2–8
TIMEBASE Controls...........................................................2–9
Vertical Controls................................................................2–10
TRIGGER Controls...........................................................2–11
ZOOM................................................................................2–12
CURSORS/MEASURE....................................................2–14
Waveform Parameters.....................................................2–16
Summed Averaging..........................................................2–17
Fast Fourier Transform (FFT)..........................................2–20
Waveform Storage ...........................................................2–21
Save and Recall Setup.....................................................2–23

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Performing the most common measurements using the
scope, in a series of easy-to-follow, step-by-step tutorials.
)LUVW6WHSVLQ0HDVXULQJ ........................................................3–2
The basic steps for setting up practically any measurement.
'LJLWL]LQJZLWK$OO(LJKW%LWV ................................................3–6
How to set up the scope for digitizing on all eight bits.
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Parameter measurement and statistical values made easy.
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Ensure accurate measurements.
8VLQJ$YHUDJHWR5HPRYH1RLVH .....................................3–26
Reduce non-systematic noise and improve the signal-to-noise ratio.
'9LHZLQJZLWK$QDORJ3HUVLVWHQFH ...........................3–31
Explore the new dimensions Analog Persistence reveals.
&RORUVWKDW/LQNDQG'LVWLQJXLVK......................................3–39
Color Association makes signal viewing clearer and easier.
&XWWLQJ'HDGWLPH%HWZHHQ(YHQWV.................................3–53
For a choice of single-shot waveform segments without deadtime.
7KH6FRSHDV6SHFWUXP$QDO\]HU ...................................3–63
Perform signal power distribution as a function of frequency.
3UHFLVLRQ$QDO\VLVZLWK+LVWRJUDPV ..............................3–70
Use the WPO3 option to display and calculate signal jitter.
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Process acquisitions of a few sample points.
7HVWLQJ$JDLQVWD7HOHFRP0DVN ....................................3–96
Telecom-measure pulse-shaped signals to industry standards.
6WRULQJWR5HPRYDEOH+DUG'LVN....................................3–109
The portable PC Card hard disk drive (HDD) simplifies storage.
&DOFXODWLQJRQ/RQJ:DYHIRUPV.....................................3–114
Handle longer FFTs and multiple long-waveform zoom, math and
storage.
60$57*OLWFK&DSWXULQJ ....................................................3–127
Find and capture glitches with the SMART Trigger.
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Use the SMART Trigger to increase knowledge of rare waveforms.
7ULJJHULQJRQ/RVW6LJQDOV ................................................3–144
Ideal for detecting interruptions in data streams.
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By GPIB, floppy or RS232 communication port.
7UDQVIHUULQJ,PDJHVWR3&...............................................3–158
Copy screen TIFFs and BMPs to computer.

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The title itself is explicit: this is a practical guide that
shows you what the scope can do as you operate it .
The guide offers a helping hand to both the
beginner and the experienced operator of digital
storage oscilloscopes (DSOs). It can be opened at
almost any page and used to enable you to get the
most out of the instrument.
$OO$ERXWWKH'62 ³an overview of the principles of DSO operation, including data
sampling, triggering, recording, how sampling rate affects usable
bandwidth and how long memory improves sampling rate.
*HWWLQJ6WDUWHG ³shows you around the scope and step-by-step how to capture
waveforms and perform basic measurements.
0HDVXULQJ6NLOOV ³a set of tutorials describing — again, step-by-step — how to
make the most useful measurements using the scope's advanced
functions.
“HANDS ON” FOR THE COMPLETE PICTURE IN SIGNAL CAPTURE,
VIEW AND ANALYSIS.
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Why and how is the Digital Storage Oscilloscope
(DSO) so useful? What are the many ways in
which it can be put to work for you?
Part 1 maps the digital landscape and
shows you where to find and mine its
riches. Basic concepts are explained and
the main digital concepts and techniques
outlined. The advantages of your LeCroy
scope are also covered.
Having completed Part 1, you’ll then be
ready to zoom in on your scope in Part 2.
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The digital oscilloscope is the essential instrument
used to capture, view and analyze waveforms,
measure signal characteristics and document the
output.
There are three main DS0 categories.
Top-end models with a bandwidth of around
400 MHz or more are the most suitable for R&D-type
work. The 100–200 MHz models are good for
professional and general purposes. And the
sub-100 MHz, low-cost scopes, are useful for work
on low-frequency signals.
%DVLF(OHPHQWV The way in which each element of the DSO works separately
and in conjunction with the other elements:
ØAmplifier —amplifies the input signal so that it can be
measured
ØAnalog-to-Digital Converter (ADC) — converts the
analog signal into digital form by translating it into a
series of sample points that are then measured and
transformed into digital codes representing the signal
samples
ØAcquisition Memory System — stores resulting digital
data
ÛSystem Memory of up to 64 MB

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ØProcessor — controls the entire system and performs
special monitoring and measurement functions
ØDisplay System — translates stored data into a graphic
display of the signal.
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The character of your signals will determine the primary
specifications of the DSO you will want to use. While your DSO’s
secondary specifications will be determined by the demands of your
applications. In assessing the overall signal representation quality of
a digital oscilloscope, particular consideration needs to be given to
the cardinal parameters of bandwidth, sample rate, and
acquisition memory length.
%DQGZLGWK The bandwidth specification of a DSO indicates the ability of its front-
end amplifier to faithfully track an incoming signal. The DSO’s
bandwidth is defined as the frequency at which a sinusoidal input
signal has been attenuated to about 70 % of its real amplitude. This
point, at which the vertical amplitude error is about 30 %, is called the
–3 dB point. It is generally advisable to use an instrument whose

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bandwidth is five times greater than the highest frequency
component of the signal to be studied.
6DPSOH5DWH The higher the sample rate the better the signal resolution. This is
particularly important for single-shot waveform capture and
measurement. The danger with low sample rates is that important
information may be lost between samples. Accurate waveform
capture requires a sample rate of at least five times the highest
frequency component to be captured. For repetitive signals the
sample rate is a less critical factor, as the signal can be captured
over many cycles.
0HPRU\/HQJWK Acquisition memory length determines the number of input signal
samples that can be stored. The greater the capacity for stored
samples, the faster the possible sample rate for a given waveform
duration. The signal captured with a long-memory DSO has a
greater resolution, while for short-memory DSOs, the high sample
rates quoted are only available at a few fast time-base settings.
Long-memory DSOs allow operation at the highest possible sample
rate, and over a far greater number of timebase settings.
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The DSO can perform the same operations as an analog
oscilloscope and much more:
Capture of one-off (single-shot) events, stored in memory
Data stays on screen while the scope waits for the next trigger
View of the waveform before the instant of triggering, recording an
event’s cause and effect.
Analysis of signals, providing precise measurement results
Documentation of signals, and the transfer of data via storage
media to PC, or direct to print using an internal or external printer,
or to a plotter.

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The DSO’s fidelity in reconstructing the input signal is mainly affected
by these three parameters (by others, too). The bandwidth must be
sufficient to allow all the signal components to pass through the
signal-conditioning system. And the sample rate has to be high
enough to provide a good definition of the signal. Long memory
maintains the sample rate for large time windows.
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In addition to the primary specifications described above, capture
techniques, trigger system, number of channels, availability and type
of probes, and ADC specification all impact the usability and
performance of the DSO.
$FTXLVLWLRQ7HFKQLTXH Single-shot acquisition is the DSO’s basic acquisition technique,
which makes the instrument very suitable for the study of signal
phenomena that have a low-repetition rate or are not repeated —
hence
single- shot. The timebase sweeps and stops at a time after
receiving the trigger signal defined by the user. The captured input
data signal is transferred to memory for viewing, measurement and
analysis.
The DSO may also employ a technique called Random Interleaved
Sampling (RIS) to increase its effective sampling rate in viewing
repetitive signals. LeCroy’s high-performance model has a maximum
rate of 10 giga-samples per second.
For slower timebases, there exists Roll Mode, where the signal
being acquired can be displayed in real time while being captured in
memory, scrolling as on a strip-chart recorder.
Because digital scopes acquire input signals by sampling, they can
miss glitches at the lower sample rates. But LeCroy’s Peak Detect
System captures glitches occurring between these samples. When
the system is activated, the scope samples at a very fast rate,
continuously checking for glitches using a built-in algorithm.
Meanwhile, it displays information in accordance with the sweep rate
actually set. When a glitch is detected, the scope will display it as a
thin spike on the displayed waveform.
Another of the LeCroy scope’s methods for acquiring signals is
Sequence Mode, which captures individually multiple trigger events

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separated by dead periods that would otherwise be unacquirable.
When triggering in this mode, the scope grabs a pre-programmed
number of samples, resets its trigger, and awaits another event. The
resulting waveform is a splicing together of all the waveforms
acquired. This eliminates the information-poor deadtime that would
appear between triggers if the scope triggered on the first event and
then continued to run. Sequence Mode allows acquisition of closely-
spaced trigger events.
$QDORJ²'LJLWDO&RQYHUVLRQ High-speed DSO performance is made possible by the use of
advanced ADCs whose vertical resolution will guarantee a clear
representation of the signal. These ADCs measure the voltage level
at evenly spaced intervals and store the digitized value in high-speed
dedicated memory. The shorter the intervals, the faster the digitizing
rate — and the finer the time structure able to be seen. The higher
the resolution of the ADC, the better is its sensitivity to small voltage
changes. And the greater its memory capacity, the longer the
recording time that will be available.
1XPEHURI&KDQQHOV Your LeCroy DSO has four channels, as well as an external trigger
channel and a CAL BNC output connector. The CAL BNC can be
used as the source of a calibration signal, an output pulse on the
occurrence of each trigger, or an output pulse signaling a Pass/Fail
condition.
7ULJJHULQJ The power of a DSO in any given application depends on a
combination of several features, and particularly on whether it is able
to trigger on the event of interest. A trigger system far more
sophisticated than that found in conventional oscilloscopes is needed
for capturing rare phenomena such as glitches or spikes, logic
states, missing bits, timing jitter, microprocessor crashes, network
hang-ups or bus contention problems. Your LeCroy scope
incorporates this more sophisticated system.
Unlike manufacturers who put their ‘best’ trigger design into their
more expensive scopes and a less adequate one into the lower-
bandwidth, economy models, LeCroy offers all its DSO users, at
every bandwidth, both a standard edge trigger
and a powerful
SMART Trigger for capturing elusive events.

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A push-button control switches from one of these triggers to the
other. Moreover, the LeCroy DSO has a variety of advanced trigger
modes. The functioning of these modes is based on two important
features. The first is the ability to preset the logic state of the trigger
sources: channels CH 1, CH 2, CH 3, CH 4, and EXT and EXT/10.
The second is a counter that can be preset and used to count a
number of events between 1 and 109, or to measure time intervals
from 2.5 ns–20 s in steps of 1 % of the time scale.
In combination, these twin capabilities open the door to a wide variety
of trigger conditions. But great care has been taken to maintain the
SMART Trigger’s ‘user-friendliness’, without losing this versatility.
Icons illustrate the trigger conditions on-screen for every mode.
6LJQDO9LHZLQJ 
The DSO’s display system translates stored data into a graphic
representation of the signal and shows it on the screen. Also
displayed are internal status and measurement results, as well as
operational, measurement and waveform-analysis menus.
The LeCroy DSO’s large screen and a waveform grid that fills the
viewing area accelerate visual processing and facilitate more
effective communication of on-screen information. Other advanced
display techniques give major performance improvements over
conventional analog or digital scopes. A hardcopy of the screen
contents can be produced at the press of a front-panel screen-dump
button. Multiple waveforms can be viewed on separate grids,
ensuring the best utilization of the ADCs’ dynamic range. XY and
variable persistence displays are also provided, as is Enhanced
Resolution Mode.
A wide range of processing functions can be performed. Four traces
— A, B, C and D — are available for zooming exclusively or together
with waveform mathematics. The horizontal expansion can be huge,
greatly improving the time resolution on the viewed trace. Several
traces can be zoomed onto the same waveform for precise timing
measurements.

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Measuring signal characteristics and analyzing circuit
performance is at the heart of test engineering.
Most DSOs can measure parameters, but analyzing their
statistics can be a time-consuming chore. LeCroy’s parameter
measurements and statistics allow worst-case analysis of circuit
performance and make the process much faster.
3XOVH3DUDPHWHUV Cursor readouts allow use of full ADC resolution to measure a
waveform’s absolute or relative times and amplitudes. However,
most users measure the same waveform parameters, such as
risetime, falltime, pulse width, overshoot, undershoot, peak
voltage, peak-to-peak voltage, maximum, minimum, standard
deviation, rms value, frequency, and period. These and many
other parameters are available using your LeCroy oscilloscope.
:DYHIRUP0DWK Waveform math allows the display of final answers, rather than
raw data. For example, inputs from voltage and current
transformers can be multiplied together to display power. An
important LeCroy DSO feature is the ability to ‘daisy-chain’ math
functions: a power trace can be integrated to display energy, for
instance.

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A great advantage of digitizing is the added ability to analyze data.
Once the analog signal has been converted into digital data, the data
can be analyzed either by the DSO’s internal digitizer processor or by
an external computer. Most current digitizers have a wide analysis
spectrum built-in. Depending on the model and its options, LeCroy
DSOs offer a selection of the following analytical features.
7LPH'RPDLQ The optional time domain waveform analysis package — includes
zooming, summed averaging of up to one million sweeps,
derivatives, logarithm, square root, absolute value, ratio, six digital
filters and standard arithmetic operations. The zoom feature on high-
performance models expands the waveform so that the individual
data are very clearly separated.
)UHTXHQF\'RPDLQ Spectrum analysis greatly extends the DSO’s processing power and
offers two clear advantages over FFT (Fast Fourier Transform)
analyzers: higher frequency components, and the ability to monitor
both time and frequency information. Fourier transform converts
sampled waveform information into a unique set of sine wave
components. The data is usually plotted as amplitude vs frequency,
exposing information not easily visible in the time domain (amplitude
vs time). Ideally, it can be used for such analyses as measuring
frequency components of communication signals and monitoring drift
in an oscillator. The frequency resolution of an FFT is directly
proportional to the number of time-domain points the FFT algorithm
can handle.
6WDWLVWLFDO'RPDLQ The existence of measured waveforms in digital representations
permits convenient use of the data inherent in those measurements.
As well as analysis of signals in the frequency domain and the ability
to perform mathematical operations and signal averaging on data,
trends can be determined and histograms of the data analyzed.
The histogram is a graph of the distribution of values of a measured
parameter. For example, when measuring the risetime of a repetitive
signal for which all the measurements are equal, the histogram will
be a straight vertical line without breadth. However, variations in
risetimes create a plot with some horizontal structure, implying
variations in the measurements. Your LeCroy DSO is able not only to

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create such histograms, but also to allow measurement of their
characteristics. This is extremely useful when analyzing pulse
amplitudes, widths or timing jitter.
Other LeCroy analysis techniques include Pass/Fail testing, Mask
Comparison testing, EYE-diagram analysis for telecom
applications, and the specialized testing for magnetic media
applications, DDM (Disk Drive Measurements) and PRML (Partial
Response Maximum Likelihood).
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Storage and recording functions are key requirements in many test
applications. The LeCroy digital scopes produce excellent output, in
the form of either digital data or hard-copy records.
5HPRYDEOH+'' Files saved in the TIFF format can be imported into PCs and other
computers. The portable PC Card HDD (Hard Disk Drive) is a
PCMCIA Type III device much faster than a floppy disk and with far
greater capacity that can be popped in and out of your LeCroy DSO
or computer. There is an HDD adapter on the rear panel of your
scope.
Note that test data can be processed far more quickly
inside a DSO,
and saved on the scope’s internal HDD, than by transfer via GPIB
link to computer.
The PC Card Memory Card drive and built-in floppy disk drive —
located on the front panel of your LeCroy DSO — can also be used
to store waveforms and screen shots. The built-in thermal printer is
quick and convenient for producing a screen-output plot. The scope
can output to a printer through its parallel port.

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,QWHUIDFHV Your LeCroy DSO can be controlled remotely through its IEEE-488
or RS-232 ports. As well as storage, printing and transfer to memory
devices, the scope offers push-button transfer of waveforms and
settings to the LW series of arbitrary waveform generators. This
enables, for example, a reference waveform to be captured from a
known good device and used as a test stimulus applied to other
devices.

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Part 2 introduces the scope’s main features and
runs through them with you. You’ll get a basic
idea of what the instrument can do and start
working with it quickly and effectively.
Following this, you’ll be ready to go on to
Part 3, and to connect your own signals to
the scope.
For complete details on all features of your
LeCroy color digital oscilloscope, see the
accompanying 2SHUDWRU·V0DQXDO.
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The main controls you’ll be using here:
$8726(783—acquires and displays repetitive signals in less than two seconds.
$1$/2*3(56,67— for the unique Analog Persistencefeature: each persistence
data map is displayed in various intensities of the trace color.
)8//6&5((1— expands the waveform and grid to fill the entire screen.
7,0(%$6(75,**(5 —includes trigger-mode, -level and -position selection, as well as
TIME/DIV control.
&+$11(/6 — turns the input channels on and off, and controls the OFFSET and
the vertical sensitivity for input channels. The VAR button, also in this
group of controls, gives variable, fully calibrated sensitivity throughout
the scope’s range.
6<67(06(783 — the dark-gray menu-
entry buttons that dominate this group access
the main on-screen menus and the acquisition, processing, and
display modes. The two knobs adjust menu values and command
cursors.
0HQX%XWWRQV.QREV — seven buttons and two knobs that control on-screen menu
selection. Each controls the menu to its immediate left on the screen.
=2200$7+ — allows the selected trace to be moved and expanded or have a
mathematical operation applied to any of the scope’s channels or
other Zoom/Math functions.