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6 ESSENTIAL TIPS FOR GETTING THE
Most Out of Your Oscilloscope
Contents
6 Essential Tips for Getting
The Most Out of Your Oscilloscope
TIP 1
TIP 2
Get Started
with Basic Triggering
Remember
Probing Matters
Go to Tip 1 & gt;
TIP 3
Go to Tip 2 & gt;
TIP 4
TIP 5
Scale Signals Correctly
Go to Tip 3 & gt;
TIP 6
Use the Right
Acquisition Mode
See More Detail Using
Advanced Triggering
Use Integrated Protocol
Decoders for Serial Buses
Go to Tip 4 & gt;
Go to Tip 5 & gt;
Go to Tip 6 & gt;
TIP 1
Get Started with Basic Triggering
TRIGGERING
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SCALING
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6 Essential Tips for Getting the Most Out of Your Oscilloscope | 3
TIP 1
Get Started with Basic Triggering
Photo finish of your signals
Oscilloscope triggering is one of the most important capabilities you need to
understand when trying to get the most out of your oscilloscope. It is especially
important when attempting to make measurements on many of today’s more
complex digital signals.
Think of oscilloscope triggering as a racecar photo finish. Although it’s not a repetitive
event, the camera’s shutter must be synchronized to the first racecar’s front bumper
at the instant in time that it crosses the finish line. Viewing untriggered waveforms on
an oscilloscope is just like randomly taking photos of the race. Between the start and
end of the race, you’ll see a lot of racecars but you won’t get the information you
really need.
Using the scope’s default trigger settings, the oscilloscope will trigger on a rising
edge of the signal. This point in time is shown at center-screen (both horizontally and
vertically).
Which channel you want to use as the source; the trigger level voltage setting; what
kind of edge you want to trigger on (rising, falling); as well as horizontal and vertical
position controls are all selectable to help you acquire ‘photos’ of the exact event
you are looking for.
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LEARN MORE
2-minute Guru: Triggering Basics
App Note:
Evaluating
Oscilloscope
Fundamentals
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6 Essential Tips for Getting the Most Out of Your Oscilloscope | 4
TIP 2
Remember Probing Matters
TRIGGERING
PROBING
SCALING
ACQUISITION MODE
ADVANCE TRIGGERING
PROTOCOL DECODE
6 Essential Tips for Getting the Most Out of Your Oscilloscope | 5
TIP 2
Remember Probing Matters
Choose the right oscilloscope probe
Probes are used to connect your oscilloscope to your device under test (DUT),
and they are crucial for optimizing signal integ ity. There are literally hundreds
r
of different oscilloscope probes available, so how do you choose the right one?
There’s no single answer because all designs are different. But, here are some
different probe characteristics you’ll want to consider before making a decision.
Bandwidth
A probe’s bandwidth describes how high of a frequency the probe is able to pass
on to the oscilloscope. Your probes should be at least 3x to 5x faster than the
fastest signal you want to see.
Attenuation ratio
Probes have different (sometimes switchable) attenuation ratios that change how
the signals are fed into your oscilloscope. A higher attenuation ratio will allow you
to look at higher voltages, but it will also make the scope’s internal amplifier noise
more pronounced. Low attenuation ratios means you’ll see less scope noise but
have more system loading distorting your signal.
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6 Essential Tips for Getting the Most Out of Your Oscilloscope | 6
Probe loading
No probe is able to perfectly reproduce your signal because when you connect a
probe to a circuit, the probe becomes part of that circuit. This phenomenon is called
loading. Unnecessarily loading your system can lead to inaccurate measurements
and even change the shape of the waveform on your oscilloscope screen!
Resistive loading: It is a good idea to make sure the resistance of your probe is
greater than ten times the resistance of the source in order to get an amplitude
reduction of less than ten percent.
Capacitive loading: Make sure the specified capacitance of the probe fits within
your design parameters.
Inductive loading: Reduce inductive loading (appears as ringing in your signal) by
using the shortest lead possible.
Passive vs. active probes
Passive probes are typically inexpensive, easy to use, and rugged. They are a
ver atile and accurate type of probe.
s
Passive probes usually produce relatively high capacitive loading and low resistive
loading. They are useul for probing signals with bandwidths less than 600 MHz.
f
Once this frequency is surpassed, an active probe is needed.
LEARN MORE
Blog Post:
Quick Steps
to Accurate
Scope Probing
Active probes use active components to amplify or condition a signal and require a
power supply to operate. They are able to support much higher signal bandwidths.
Active probes are considerably more expensive and less rugged than passive
probes. Active probes also typically have less loading than passive probes.
Passive probes are great for qualitative measurements such as checking clock
frequencies, browsing for bugs, etc. But, active probes excel in quantitative
App Note:
Eight Hints
for Better
Scope Probing
measurements like output ripple or rise times. While active probes cost
more than passive probes, they can make a big difference for your
measurement accuracy.
TRIGGERING
PROBING
SCALING
ACQUISITION MODE
ADVANCE TRIGGERING
PROTOCOL DECODE
6 Essential Tips for Getting the Most Out of Your Oscilloscope | 7
TIP 3
Scale Signals Correctly
TRIGGERING
PROBING
SCALING
ACQUISITION MODE
ADVANCE TRIGGERING
PROTOCOL DECODE
6 Essential Tips for Getting the Most Out of Your Oscilloscope | 8
TIP 3
Scale Signals Correctly
Horizontal scaling
Horizontal scaling is important to consider when making
time- dependent measurements. When you change the
horizontal scaling (time-per-division) of your signal, you are also
Proper signal scaling is crucial.
changing the total signal acquisition time. The signal acquisition
The oscilloscope’s sample rate and bits of resolution affect your measurement accuracy,
time in turn affects the sample rate of the scope. The equation that
and proper signal scaling allows you to optimize your measurements.
describes this relationship is:
Sample Rate = Memory Depth/Acquisition Time
Memory depth is a fixed value, and the acquisition time is fixed by
adjusting the time per division setting on your oscilloscope. As the
acquisition time increases, the sample rate will have to decrease in
order to fit the entire acquisition into the scope’s memory. Having
an appropriate sample rate for time-dependent measurements
(frequency, pulse width, rise time, etc.) is important.
100 KHz clock signal
Increasing the voltage-per-division scaling
Both of these screens are showing the same signal but with different scaling— resulting measurements
deliver significantly different results.
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6 Essential Tips for Getting the Most Out of Your Oscilloscope | 9
Vertical scaling
Just as horizontal scaling is important for time-specific measurements, vertical
scaling is important for vertically-dependent measurements (peak-to-peak,
RMS, max, min, etc.). By simply increasing the vertical scaling of the signal, you
can get a much more accurate measurement with a standard deviation that is
much smaller. Why does vertical scaling affect measurements? Just as horizontal
(time-dependent) measurements are affected by sample rate, vertical (amplitudedependent) measurements are affected by bits of resolution.
WATCH NOW
LEARN MORE
Webcast:
Make Great Oscilloscope
Measurements (6:24)
TRIGGERING
Electronic
Design Article:
Make Great
Oscilloscope
Measurements
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6 Essential Tips for Getting the Most Out of Your Oscilloscope | 10
TIP 4
Use the Right Acquisition Mode
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6 Essential Tips for Getting the Most Out of Your Oscilloscope | 11
TIP 4
Use the Right Acquisition Mode
What are oscilloscope acquisition modes?
If you want confidence in your oscilloscope readings, you need to understand the
strengths and weaknesses of different acquisition modes: normal, averaging, high
resolution, and peak-detect acquisition. Acquisition modes are finely-tuned sampling
algorithms. By varying the sample rate of the scope’s analog-to-digital converter
Normal mode
Ideal for day-to-day debugging.
Averaging mode
Helpful for removing random noise on synchronous,
stable signals.
Useful for maximizing your bits of
(ADC) and selectively plotting or combining sample points, different characteristics of
a signal can be observed.
High-resolution mode
Normal acquisition mode
Peak-detect acquisition mode
resolution while debugging synchronous or
asynchronous signals.
Valuable for gaining insight into unusually high or low
points that may not typically be seen.
Normal acquisition mode is the default mode for oscilloscopes. The ADC
samples, and the scope decimates down to the desired number of points and plots
the waveform. It’s best to use normal acquisition mode for day-to-day debugging
tasks because it gives a good general representation of your signal. It’s a safe mode
to use and has no significant caveats.
Averaging acquisition mode
Averaging mode takes multiple waveform captures and averages them
together. The main benefit of averaging acquisition mode is that it averages out
the random noise on your signal; this allows you to see just the underlying signal.
Averaging acquisition mode should be used only with periodic signals and with a
stable oscilloscope trigger. Averaging mode is great for viewing or characterizing very
stable periodic waveforms.
The screen on the right is with averaging and there is
significantly more detail visible.
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6 Essential Tips for Getting the Most Out of Your Oscilloscope | 12
High-resolution mode
High-resolution mode is another form of averaging. However, instead of waveformto-waveform averaging, it is point-to-point averaging. Essentially, the ADC
oversamples the signal and averages neighboring points together. This mode uses
a real-time boxcar averaging algorithm that helps reduce random noise. It also can
yield a higher number of bits of resolution.
High-resolution mode isn’t as effective at reducing random noise as the averaging
mode discussed earlier, but it has some distinct advantages. Because highresolution mode doesn’t depend on multiple captures, it can be used with aperiodic
signals and unstable triggers. This makes high-resolution mode much better than
averaging mode for general-purpose debugging.
Peak-detect acquisition mode
Peak-detect acquisition mode functions similar to high-resolution mode. The ADC
oversamples the signal and selectively chooses which points to display. But instead
of averaging these points together, peak-detect mode chooses the highest and
the lowest points and plots them both. This is useful because it can provide
insight into any unusually high or low points that might be otherwise hidden. Peakdetect mode is best used for detecting glitches or viewing very narrow pulses.
LEARN MORE
WATCH NOW
2 Minute
Guru: Weird
Acquisition
Modes
TRIGGERING
Webcast:
Make Great
Oscilloscope
Measurements
(23:50)
PROBING
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PROTOCOL DECODE
6 Essential Tips for Getting the Most Out of Your Oscilloscope | 13
TIP 5
See More Detail Using
Advanced Triggering
TRIGGERING
PROBING
SCALING
ACQUISITION MODE
ADVANCE TRIGGERING
PROTOCOL DECODE
6 Essential Tips for Getting the Most Out of Your Oscilloscope | 14
TIP 5
See More Detail Using
Advanced Triggering
In TIP 1 we talked about basic triggering, but there are many more triggering options
to choose from.
Rise/fall time trigger
Helpful if there’s an impedance mismatch or loading
on your system that’s causing your edges to be too
slow.
Setup and hold time trigger
Usually used to trigger on setup and hold timing
violations.
Built-in protocol triggers
Extremely useful if you are working with serial buses.
Rise/fall time trigger
The rise/fall time trigger looks for a rising or falling edge transition from one level
to another level in greater than or less than a certain amount of time. It triggers on
signals that change state either too fast or too slow. This trigger is helpful to see
if there’s an impedance mismatch or some extra loading on your system that is
causing your edges to be too slow.
A setup and hold time trigger is used for any data and clock signal. One oscilloscope
channel probes the clock signal and another channel probes the data signal. Setup
time is the time a data signal level must be present before the clock edge. Hold time
is the time a data signal level must remain after a clock edge. This is an important
trigger because digital designs require that the data line’s state be setup (0 or 1) for
a certain amount of time before the clock edge occurs. Set the trigger conditions to
your specified setup and hold requirements to check for violations in your design.
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6 Essential Tips for Getting the Most Out of Your Oscilloscope | 15
Protocol triggers
Many oscilloscopes today have built-in protocol triggers. These are extremely useful if
you are working with serial buses. For each of these different buses, there is a series of
different triggers (Start condition, Stop condition, Missing Ack, Address with no Ack and
more).
Aerospace/Defense
ARINC 429, MIL-STD 1553, etc.
Automotive
CAN, I2C, SPI, etc.
Computer
USB, etc.
You can begin your debugging by triggering on a start condition, which will give you a
stable view of the packets coming through and insight into how your system is operating.
If you’re getting system errors or want to prove that everything’s functional, you can even
trigger exclusively on errors. This will allow you to focus only on the areas causing
problems and not waste time wading through hundreds of error-free packets. If your
oscilloscope has segmented memory, you can turn it on and exclusively capture errors
over very long periods of time.
LEARN MORE
WATCH NOW
Webcast:
Advanced
Triggering
(14:30)
TRIGGERING
PROBING
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ACQUISITION MODE
ADVANCE TRIGGERING
PROTOCOL DECODE
6 Essential Tips for Getting the Most Out of Your Oscilloscope | 16
TIP 6
Use Integrated Protocol
Decoders for Serial Buses
TRIGGERING
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SCALING
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6 Essential Tips for Getting the Most Out of Your Oscilloscope | 17
TIP 6
Use Integrated Protocol
Decoders for Serial Buses
Protocol decode
Depending on what type of device you’re testing, you might need to test certain
serial buses (such as CAN and LIN for automotive and I²C and RS-232 for
embedded designs). Oscilloscopes can characterize the analog quality of these
signals by making physical layer measurements.
As described in Tip 5, a protocol trigger can help capture a specific instance or event
on the bus, which is tremendously useful. However, many of the serial buses used
today are encoded in a hexadecimal format and can be difficult to understand. An
integrated protocol decoder translates those events into a more useful format.
Hardware-based decoding
Hardware-based decoding provides a real-time update of the decode trace. This
enhances the scope’s probability of capturing and displaying infrequent serial bus
communication errors, such as stuff bit errors, form errors, acknowledge errors, CRC
errors, and error frames.
Expanded view of the hexadecimal decode trace.
Expanded view of symbolic decode trace.
LEARN MORE
WATCH NOW
2-Minute
Guru:
Protocol
Decoding
TRIGGERING
Webcast:
Debugging
Serial
Buses
PROBING
SCALING
Example: Above you see an oscilloscope triggering on and decoding a CAN
bus in a hexadecimal format, frame 0x201. There are also two subsets of that
screen, one decoded symbolically and one in its native hexadecimal format.
In this example, the oscilloscope triggered on frame ID 0x201HEX, which
correlates to 010 000 0001Binary. The decoder translates captured data into
useful information such as “Speed = 852.52 rpm” – instead of just bits.
ACQUISITION MODE
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PROTOCOL DECODE
6 Essential Tips for Getting the Most Out of Your Oscilloscope | 18
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Information is subject to change without notice. | 5992-2095EN © Keysight Technologies, 2019 | Published in USA, February 22, 2019 | keysight.com