HP 54645A, 54645D User's And Service Manual

About this Manual

We’ve added this manual to the Agilent website in an effort to help you support
your product. This manual is the best copy we could find; it may be incomplete
or contain dated information. If we find a more recent copy in the future, we will
add it to the Agilent website.

Support for Your Product

Agilent no longer sells or supports this product. Our service centers may be able
to perform calibration if no repair parts are needed, but no other support from
Agilent is available. You will find any other available product information on the
Agilent Test & Measurement website,

www.tm.agilent.com.

HP References in this Manual

This manual may contain references to HP or Hewlett-Packard. Please note that
Hewlett-Packard's former test and measurement, semiconductor products and
chemical analysis businesses are now part of Agilent Technologies. We have
made no changes to this manual copy. In other documentation, to reduce
potential confusion, the only change to product numbers and names has been in
the company name prefix: where a product number/name was HP XXXX the
current name/number is now Agilent XXXX. For example, model number
HP8648A is now model number Agilent 8648A.

User and
Service Guide

Publication Number 54645-97012
December 1997 (pdf version Nov 1998)

For Safety Information, Warranties, and Regulatory information,
see the pages behind the Index.

© Copyright Hewlett-Packard Company 1996-1997
All Rights Reserved

HP 54645A Oscilloscope and
HP 54645D Mixed-Signal
Oscilloscope

The HP 54645A/D at a Glance

Display shows current i nput signals

•

Eighteen (18) channels i n m ai n m ode;
2 scope and 8 timing channels in
delayed mode (HP 54645D)

•

Indicators for peak, av g, or normal
acquisition, time bas e, channel
activity, trigger and acquisition status

•

Softkey labels

•

Measurement results

Channel Controls select, position, and
label inputs

•

Turn channels on or off in di vidually
or in groups of 8 (HP 54645D)

•

Rearrange order of channels to
group related signals ( HP 54645D)

•

Create and display label s to identify
channels ( HP 54645D)

General Co ntrols measure, save and
restore results, and configure the
oscilloscope

•

Make autom atic time and frequency
measurements

•

Use cursors to make ma nual
measurements

•

Save or recall measure m ent
configurat i ons or previous results

•

Autoscale performs simple
one-button s etup of the oscilloscope

Horizontal Controls sel ect sweep speed
and delay parameters

•

Sweep speeds from 5 ns to 50 s/div
(2 ns to 50s/div for HP 54645A)

•

Delay control moves waveform
display to point of interest

•

Delayed mode and delay allow
zooming in to show a port i on of
waveform in detail (spli t screen)

Storage Keys begin and end data
acquisition

•

Run/Stop starts and stops continuous
acquisitions

•

Single perf orm s one acquisition

•

Autostore a ccum ulates and displays
the results of multiple acquisitions

•

Erase clears the current ac qui sition
and all acc um ul ated data

Trigger Key s define what da ta t he
oscilloscope will trigger on

•

Source key (H P 54645A) allows
conventional oscilloscope triggering

•

Edge mode al l ow s triggering on a
positive or negative edge of any
single channel (HP 54 64 5A/D)

•

Pattern mode allows trig geri ng on a
pattern of channels either high, low,
or don’t care, with an opti onal single
edge qualifier (HP 54645D)

•

Advanced m ode allows se quential
triggers, combined patterns, patterns
and edges, pattern durations, glitch
(HP 54645A/D), and TV (HP 54645D)

Softkeys ext end the functionality of
command keys

Select measurement type s, operating
modes, trigger specifications, lab el data,
and more

Channel Inpu ts through a flexibl e
probing sys tem

•

Sixteen channels throug h a dual
8-channel cable with micro-grabbers
(HP 54645D)

•

Set logic levels as TTL, CMOS, ECL,
or to a user-definable vol tage
(HP 54645D)

ii

In This Book

This manual will guide you in using and
servicing the HP 54645A Oscilloscope
and the HP 54645D Mixed-Signal
Oscilloscope. This manual is organized in
chapters as shown in the bleeder tab
titles to the right.

Front-Pa nel Overview

2

Triggering HP 54645A/D
Oscilloscopes

3

MegaZoom C oncepts and
Oscilloscope Operation

4

Making M easurements with
HP 54645A/D Oscilloscopes

5

Using Option 00 5
Enhanced TV/Video Trigg er

6

Test ing, A d justing,
and Troubl eshooting

7

Replacement Parts

8

Getting Started

1

Performance Characteristics

9

Messages

10

Glossary

Index

iii

iv

Contents

1 Getting Started

Preparing the Oscilloscope 1–4

Check package contents 1–5
Adjust the handle 1–9
Connect the cables 1–9
Power-on the oscilloscope 1–10
Using the digital probes to probe a circuit 1–11
Using the oscilloscope probes 1–13
Adjust display brightness 1–13

2 Front-Panel Overview

Important Oscilloscope Considerations 2–2
HP 54645A/D Front Panels 2–6
Description of Front-Panel Areas 2–8

Front-Panel Operation 2–16

To use oscilloscope channels to view a signal 2–17
To use digital channels to view a signal 2–18
To display signals automatically using Autoscale 2–19
To apply the default factory configuration 2–20
To adjust oscilloscope vertical scaling 2–21
To turn analog channels on and off 2–24
To rearrange the analog channels 2–24
To turn digital channels on and off (HP 54645D) 2–25
To rearrange the digital channels (HP 54645D) 2–26
To operate the time base controls 2–27
To start and stop an acquisition 2–28
To use the Entry and Select knobs 2–29
To make cursor measurements 2–30
To use delayed sweep 2–32
To modify the graticule 2–33
To print the display 2–34

Contents–1

3 Triggering HP 54645A/D Oscilloscopes

Selecting Trigger Modes and Conditions 3–3

To select a trigger mode: Auto Lvl, Auto, Normal 3–3
To use holdoff 3–5
To trigger on a complex waveform 3–6

Triggering the HP 54645A Oscilloscope 3–7

To use external triggering 3–7
To trigger on an edge 3–8
To use glitch triggering 3–9
To use line triggering 3–10
To use TV triggering 3–10

Triggering the HP 54645D Mixed-Signal Oscilloscope 3–11

Trigger types 3–12
To define an edge trigger 3–16
To use line triggering 3–16
To define a pattern trigger 3–17
To use glitch triggering 3–18
To define an advanced pattern trigger 3–19

4 MegaZoom Concepts and Oscilloscope Operation

MegaZoom Concepts 4–3

Deep Memory 4–4
Oscilloscope Responsiveness 4–5
Display Update Rate 4–6
Display Modes 4–7
Pan and Zoom 4–18
Recovering the waveform on the screen 4-21
Changing the time reference position 4–22

Contents

Contents–2

Run/Stop/Single/Autostore/Erase Operation 4–29

Acquiring Data 4–30
Memory Depth/Record Length 4–31
To run and stop an acquisition 4–33
To take a single trace 4–33
To capture a single event 4–34
To use Autostore 4–36
To Autostore Multiple Single Events 4–37
To erase the waveform display 4–38
Using Digital Channels to Probe Circuits 4–39

Saving and Recalling the Configuration 4–43

Using memories to save and recall configurations 4–43
To save, recall, and clear traces 4–46
To save or recall front-panel setups 4–48
To reset the HP 54645A/D instrument setup 4–48

Configuring the Mixed-Signal Oscilloscope 4–51

To change the logic threshold for input signals 4–51

Using Labels on the Mixed-Signal Oscilloscope 4–53

To turn the label display on or off 4–53
To assign a predefined label to a channel 4–54
To define a new label 4–56
To initialize the label list 4–58

5 Making Measurements with HP 54645A/D Oscilloscopes

Capturing Data 5–3

To use delayed sweep 5–4
To view asynchronous noise on a signal 5–6
To reduce the random noise on a signal 5–8
To capture glitches or narrow pulses with peak detect 5–11
To use channel math 5–12
To use the Roll display mode 5–13

Contents

Contents–3

To use the XY display mode 5–14
To analyze video waveforms 5–18

Measuring Waveform Data 5–22

To make cursor measurements 5–22
To make frequency measurements automatically 5–26
To make time measurements automatically 5–28
To make voltage measurements automatically 5–32

6 Using Option 005 Enhanced TV/Video Trigger (HP 54645A)

To autoscale on a video signal 6–4
To trigger on a specific line of video 6–5
To trigger on all TV line sync pulses 6–7
To trigger on a specific field of the video signal 6–8
To trigger on all fields of the video signal 6–9
To trigger on odd or even fields 6–10
To analyze video waveforms with Option 005 6–12

7 Testing, Adjusting, and Troubleshooting

Testing, Adjusting, and Troubleshooting 7–2

Solving Problems with HP 54645A/D Oscilloscopes 7–3

If there is no trace display 7–4
If the trace display is unusual or unexpected 7–5
If you can’t see a channel 7–5
If you can’t get any response from the oscilloscope 7–6

Getting Service 7–7

To return the oscilloscope to Hewlett-Packard 7–8

Verifying Oscilloscope Performance 7–9

To construct test connectors for digital channels 7–9
To test the digital channels 7–11

Contents

Contents–4

Testing Threshold Accuracy 7–12

To set up and connect the equipment 7–13
To verify threshold accuracy 7–14
To check the output of the CALIBRATOR 7–15
To verify voltage measurement accuracy 7–16
To verify bandwidth 7–19

To verify horizontal ∆t and 1/∆t accuracy 7–22
To verify trigger sensitivity 7–24
To verify vertical output on Option 005 7–27

Adjusting the Oscilloscope 7–29

To adjust the power supply 7–30
To perform the self-calibration 7–33
To adjust the low-frequency compensation 7–35
To adjust the high-frequency pulse response 7–36
To adjust the display 7–38
To adjust the Option 005 offset (R15) (HP 54645A) 7–40

Troubleshooting the Oscilloscope 7–41

To construct your own dummy load 7–42
To check out the oscilloscope 7–43
To clear error messages 7–46
To check the Low Voltage Power Supply 7–48
To run the internal self-tests 7–50
To troubleshoot Option 005 7–52

8 Replacement Parts

Removing and Replacing Assemblies 8–3

To remove the cabinet 8–4
To remove the fan 8–4
To remove the front panel 8–5
To remove the display 8–6
To remove the system board 8–6
To remove the front-panel BNC connectors 8–7

Contents

Contents–5

To remove the power supply 8–8
To remove the keyboard 8–9
To remove the handle 8–9
Replacing the Option 005 board 8–10

Replaceable Parts 8–11

To order a replacement part 8–12

9Performance Characteristics

HP 54645A/D Oscilloscopes 9–3
HP 54645D Digital Channels 9–4
HP 54645A/D Oscilloscope Digitizing System 9–5
HP 54645D Logic Digitizing System 9–5
HP 54645A/D Time Base 9–6
HP 54645A/D Oscilloscope Trigger System 9–7
HP 54645A Oscilloscope Trigger System 9–8
HP 54645D Mixed-Signal Oscilloscope Trigger System 9–8
HP 54645A/D Setup Functions 9–9
HP 54645A/D Power Requirements 9–9
HP 54645A/D General Characteristics 9–10
Option 005 General Performance Characteristics 9–11
Option 005 Trigger System 9–11

10Messages

Messages 10–3

Glossary

Index

Contents

Contents–6

1

Getting Started

Getting Started

When you use the HP 54645A/D Oscilloscopes to help test and
troubleshoot your systems, you will do the following:

• Prepare the oscilloscope by connecting it to power and setting up

the handle and screen brightness as desired.

• Define the measurement problem by understanding the parameters

of the system you wish to test and the expected system behavior.

• Set up channel inputs by connecting the probes to the appropriate

signal and ground nodes in the circuit under test.

• Define the trigger to reference the waveform data to a specific

event of interest.

• Use the oscilloscope to acquire data, either in continuous or

single-shot fashion.

• Examine the data and make measurements on it using various

features.

• Save the measurement or configuration for later re-use or

comparison with other measurements.

Repeat the process as necessary until you verify correct operation or
find the source of the problem.

MegaZoom Technology Operates with Untriggered Data

With the MegaZoom technology built into the HP 54645A/D, you can
operate the oscilloscope with untriggered data. All you do is press Run
or Single while in Auto trigger mode, then examine the data to set up
a trigger.

1-2

The HP 54645A/D high-speed display can be used to isolate
infrequently changing signals. You can then use the characteristics of
these signals to help refine the trigger specification. See figure 1-2
below. For more information on triggering, data acquisition, data
examination and measurement, and configuration, see chapters
3 and 4.

Using the HP 54645A/D Oscilloscopes, and Refini ng the Trigger Spec if i cation

Figure 1-1 Figure 1-2

Getting Started

1-3

Preparing the Oscilloscope

To prepare your HP 54645A Oscilloscope or HP 54645D Mixed-Signal
Oscilloscope for use, you need to do the following tasks. After you
have completed them, you will be ready to use the oscilloscope.

In the following topics you will:

• Check package contents

• Adjust the handle

• Connect the cables

• Power-on the oscilloscope

• Use the digital probes to probe a circuit (with HP 54645D)

• Use the oscilloscope probes

• Adjust display brightness

1-4

Check package contents

•

Verify that you received the following items and any optional
accessories in the HP 54645A/D packaging.

If anything is missing, contact your nearest Hewlett-Packard Sales Office. See
figure 1-3. If the shipment was damaged, contact the carrier, then contact the
nearest Hewlett-Packard Sales Office.

Accessories Supplied Accessories Available

Power cord (see the following t abl e)
HP 54620 -6 1801 16-channel pr obe cable (HP 54 645D only)
HP 10074 A 1. 5-meter, 10:1 Pr obe with readou t (qt y 2)
HP 5090- 4356 grabber s ( in resealable plastic bag; qty 20 )
(HP 54645D onl y—supplied w i th 16- channel cable)
HP 5959-9334 2" ground lead set (qty 5)
(HP 54645D onl y—supplied w i th 16- channel cable)
HP 54645A/D User & Service Guide
HP 54645A/D Programmer’s Guide
HP 54645A / D Pro gra m m er’s Reference (3.5 " diskette)
(disk is package d w ith Programmer’ s G ui de)
1252-7310 Banana ground plug (for HP 54645D)

HP 54650 A HP-IB Interface Module
HP 54652 B RS- 232/Parallel Interface Module
HP 54654A Operator’s Trainin g Ki t
HP 54657 A Me as. / Storage Module (HP-IB)
HP 54659 B RS- 232/Parallel /M eas./Storage M odul e
HP 34810 B BenchLink Soft w are for Windows
HP 5041- 9 409 Carr ying Case
HP 5062-73 45 Rackmount Kit
HP 10070A 1.5-meter, 1:1 Probe
HP 10100C 50-Ω Termination

Options Available

Option 001 R S-0 3 Magnetic Inter ference Shield in g Added to CRT
Option 002 R E-0 2 Di splay Shield Added to CRT
Option 101 Accessory Pouch and Front-Panel Cover
Option 103 Operator’s Training Kit (HP 54654A)
Option 104 Car r ying Case (HP 5041 - 9 409)
Option 106 B enchLink Software (HP 34810B)
Power Cords (s ee t he f ol lo w in g table or the
"Replacement Parts" chapter)

Getting Started

Check package contents

1-5

Items Sup pl ie d with the HP 546 45A/D Osci ll oscopes

Figure 1-3

Getting Started

Check package contents

1-6

Optiona l Accessories f o r the HP 54645A / D Oscilloscopes

Figure 1-4

Getting Started

Check package contents

1-7

Table 1-1
Power Cords

Plug Type Cable Part

No.

Plug Description Length

in/cm

Color

Opt 903 (U.S.A.)
124V **

8120-1378 Straight (NEMA5-15P*) 90/228 Jade Gray

Opt 900 ( U . K . )
250V

8120-1351 Straight (BS136A*) 90/228 Gray

Opt 901 ( Australia)
250V

8120-1369 Straight

(NZSS198/ASC*)

79/200 Gray

Opt 902 (Europe)
250V

8120-1689
8120-2857

Straight (C EE7-Y11*)
Straight (S hi el ded)

79/200
79/200

Mint Gray
Coco Brown

Opt 906 ( Sw itzerland)
250V

8120-2104 Straight (SEV1011*) 79/200 Mint Gray

Opt 912 ( Denmark)
220V

8120-2957 Straight (DHCK107 *) 79/200 Mint Gray

Opt 917 (Africa)
250V

8120-4600 Straight (SABS164) 79/200 Jade Gray

Opt 918 (Japan)
100V

8120-4753 Straight Miti 90/230 Dark Gray

* Part number shown for plug is industry identifier for plug only.
Number show n for cable is HP pa rt number for comp lete cable incl uding plug.
** These cords ar e included in th e CSA certificat ion approval f or the equipment.

Getting Started

Check package contents

1-8

Adjust the handle

Connect the cables

1

Check to ensure that you received everything that is supplied with
the oscilloscope.

2

Connect the oscilloscope to power and turn it on.

3

Connect the cables:

If you are using this model: Do this:
HP 54645 A Oscilloscope

Connect the oscilloscope pr obe cables to osci lloscope
channels 1 and 2.

HP 54645 D Mixed-Signal
Oscillos cope

Connect the oscilloscope pr obe cables to osci lloscope
analog channel s A1 and A2.

Connect the di gi t al pro be cable to oscillo scope digital
channels D0-D15.

4

Then, connect the scope and/or digital probes to the circuit of
interest. Be sure to connect the ground leads.

You can use the front-panel calibration point as a stimulus while learning to
use the oscilloscope.

1

Grasp the handle pivot points on each side of the
instrument and pull the pivot out until it stops.

2

Without releasing the pivots, swivel the handle to
the desired position. Then release the pivots.

Getting Started

Adjust the handle

1-9

Power-on the oscilloscope

1

Connect the power cord to the rear of the
HP 54645A/D, then to a suitable ac voltage
source.

The HP 54645A/D power supply
automatically adjusts for input line voltages
in the range 100 to 240 VAC. Therefore, you
do not need to adjust the input line voltage
setting. The line cord provided is matched
by HP to the country of origin. Ensure that
you have the correct line cord. See table 1-1.

2

Press the power switch.

The HP 54645A/D performs a self-test, then
shows the display. The instrument is ready
to use.

Getting Started

Power-on t he oscilloscop e

1-10

Using the digital probes to probe a circuit

1

If you feel it’s necessary, turn off the power
supply to the circuit under test.

Turning off power to the circuit under test
would only prevent damage that might occur
if you accidentally short two lines together
while connecting probes. You can leave the
HP 54645A/D powered on because no
voltage appears at the probes.

2

Connect the digital probe cable to HP 54645D.
The digital probe cable is indexed so you can
connect it only one way. You do

not

need to

power-off the HP 54645A/D.

3

Connect a grabber to one of the probe leads. Be
sure to connect the ground lead. (Other probe
leads are omitted from the figure for clarity.)

4

Connect the grabber to a node in the circuit you
want to test.

5

For high-speed signals, connect a ground lead to
the probe lead, connect a grabber to the ground
lead, and attach the grabber to ground in the
circuit under test.

Getting Started

Using the digital probes to probe a circuit

1-11

6

Connect the ground lead on each set of channels,
using a probe grabber. The ground lead improves
signal fidelity to the instrument, ensuring
accurate measurements.

7

Repeat steps 3 through 6 until you have
connected all points of interest.

8

If you need to remove a probe lead from the
cable, insert a paper clip or other small pointed
object into the side of the cable assembly, and
push to release the latch while pulling out the
probe lead.

Replacement parts are available. See the
“Replacement Parts” chapter for details.

Getting Started

Using the d igi tal probes to probe a circuit

1-12

Using the oscilloscope probes

1

Connect the HP 10074A 1.5-meter, 10:1 oscilloscope probe BNC
connector to the channel 1 or 2 input on the HP 54645A or to channel
A1 or A2 on the HP 54645D.

2

Connect the probe grabber to the circuit point of interest. Be sure to
connect the ground lead to a ground point.

Adjust display brightness

The brightness control is at the lower left corner of the display.

•

To decrease display brightness, rotate the brightness control
counter-clockwise.

•

To increase display brightness, rotate the brightness control
clockwise.

HP 54645A/D Brightness Control

Figure 1-5

Getting Started

Using th e oscilloscope probes

1-13

1-14

2

Front-Panel Overview

Front-Panel Overview

Before you make measurements using the HP 54645A Oscilloscope and
HP 54645D Mixed-Signal Oscilloscope, you must first set up the instrument
using front-panel controls. Then, make the measurement and read the
display results. See the following pages for descriptions of controls.

The HP 54645A/D operates much like an analog scope, but it can do much
more. Spending a few minutes to learn some of this capability will take you a
long way toward more productive troubleshooting. The “MegaZoom Concepts
and Oscilloscope Operation” chapter has more detail on the things to
consider while operating your oscilloscope.

The grey keys on the front panel bring up softkey menus on the display that
allow access to oscilloscope features. The white keys are instant action keys
and menus are not associated with them.

Throughout this book, the front-panel keys are denoted by a box around
the name of the key, and softkeys are denoted by a change in the text
type. For example,

Displa y

is the grey front-panel key on the front

panel, and Normal is a softkey appearing at the bottom of the display
directly above its corresponding softkey.

Important Oscilloscope Considerations

IMPORTAN T: R ead This Information!

It is extremely important that you read and understand the following informati on!

Using Single versus Run/Stop

The HP 54645A/D both have a Single key and a Run/Stop key. When you
press Run, the trigger processing and screen update rate are optimized over
the memory depth. Single acquisitions always use the maximum memory
available—at least twice as much memory as acquisitions captured in Run
mode—and the scope stores at least twice as many samples. At slow sweep
speeds, the oscilloscope operates at a higher sample rate when Single is used
to capture an acquisition, as opposed to running, due to the increased
memory available.

2-2

Viewing Signal Detail with Display Mode

Remember how you had to constantly adjust the brightness on old analog
scopes to see a desired level of detail in a signal, or to see the signal at all?
With the HP 54645A/D, this is not necessary. The HP 54645A/D brightness
knob operates much like the brightness knob on your computer screen, so
you should set it to a level that makes for comfortable viewing, given the
room lighting, and leave it there. Then you can control the “detail” by
selecting a Display Mode: Normal, Peak Detect, or Average, as described in
the following paragraphs.

Normal Mode

Normal mode is the display mode that you will probably use for acquired
samples most of the time. It compresses up to 1 million acquisition points per
channel into a 4,000-point display record with vectors off, or a 2,000-point
record with vectors on.

The scope’s 200 MSa/s sampling speed specification means that samples are
taken every 5 ns. At the faster sweep speeds, the running display is built from
many individual triggers. If you press the Stop key, and pan and zoom
through the waveform, only the last trigger’s acquisition will be displayed.

Whether the scope is stopped or running, you see more detail as you zoom in,
and less as you zoom out. To keep from losing detail as you zoom out, switch
to the Peak Detect display mode. “Zoom” means you expand the waveform
using either the main or delayed sweep window. “Panning” the waveform
means you use the Delay knob to move it horizontally.

Peak Detect Mode

In Peak Detect display mode, any noise, peak, or signal wider than 5 ns will
be displayed, regardless of sweep speed. In Normal display mode, at faster
than 2 us/div, you would see a 5-ns peak, so peak detect has no effect at
sweep speeds faster than 2 us/div. Note that in this case the Pk status
indicator on the top line of the display is not highlighted.

Using Peak Detect and Autostore together is a powerful way to find spurious
signals and glitches.

Average Mode

Averaging is a way to pull the signal out of noise. Averaging works better than
either a bandwidth limit or a brightness control because the bandwidth is not
reduced.

Front-Pane l Ov erview

Important Os cilloscope Considerations

2-3

The simplest averaging is “smoothing.” For example, the sample rate at a
Time/Div setting of ≥ 2 µs/div allows the extra 5-ns samples to be smoothed

together, smoothing the data into one sample, which is then displayed. As
with Peak Detect, smoothing has no effect at less than 2 µs/div. Smoothing

works on a single acquisition (even untriggered and single-shot). Averaging
(4, 8, 16, 32, 64, 128, and 256) needs a stable trigger, because in this mode
multiple acquisitions are averaged together. See the chapter “MegaZoom
Concepts and Oscilloscope Operation” for more information about smoothing.

Auto Single

As in Normal run mode, auto-trigger will generate a trigger for you if one is
not found in the predetermined time from when the trigger system is armed.
To take a single-shot acquisition, if you are not particularly interested in
triggering the acquisition (for example, if you are probing a known signal),
use Auto Single mode. If a trigger exists, it will be used; if a trigger does not
exist, an untriggered or auto-triggered acquisition will be taken for later
analysis.

Using Vectors

One of the most fundamental choices you must make about your display is
whether to draw vectors (connect the dots) between the samples, or simply
let the samples fill in the waveform. To some degree, this is a matter of
personal preference, but it also depends on the waveform.

•

You will probably operate the oscilloscope most often with vectors on.
Having vectors on slows the display of the oscilloscope, thus works better
for slower sweep speeds, peak detect, or average displays, and signals with
stable triggers.

•

Having vectors off works better for fast sweep speeds, normal displays, or
unstable triggers. Complex analog signals like video and eye diagrams
show more intensity information with vectors off. Turn vectors off when
the maximum display rate is required, or when highly complex or
multi-valued waveforms are displayed.

Front-Pan el Overview

Important Os cilloscope Considerations

2-4

Delayed Sweep

Delayed sweep on the HP 54645A/D is a simultaneous display of the
waveform at two different sweep speeds. Because of the deep memory in the
MegaZoom technology, it is possible to capture the main display at 1 ms/div,
and redisplay the same trigger in the delayed display at any desired faster
time base.

There is no limit imposed on the zoom ratio between the main and delayed
displays. There is, however, a useful limit—when the samples are spaced so
far apart that they are of little value. See the chapter “MegaZoom Concepts
and Oscilloscope Operation” for more information about delayed sweep and
time reference.

Post Acquisition Processing

In addition to changing display parameters after the acquisition, you can do
all of the measurements and math functions after the acquisition.
Measurements and math functions will be recalculated as you pan and zoom
and turn on and off channels. As you zoom in and out on a signal, you affect
the resolution of the display. Because measurements and math functions are
performed on displayed data, you affect the resolution of functions and
measurements.

The two scope channels are always acquired, so you can turn them on and
look at them even if they were off during the acquisition. See “To turn digital
channels off (HP 54645D)” later in this chapter for more information about
the combination of events and displayed channels.

The XY horizontal display mode changes the oscilloscope display to
volts-versus-volts. The Roll horizontal display mode causes the waveform to
move across the screen from right to left.

Front-Pane l Ov erview

Important Os cilloscope Considerations

2-5