Describe how to use

oscilloscopes in different modes

 Oscilloscopes
• An oscilloscope, previously called an
oscillograph, and informally known as a scope
or o-scope, CRO (for cathode-ray
oscilloscope), or DSO (for the more modern
digital storage oscilloscope), is a type of
electronic test instrument that graphically
displays varying signal voltages, usually as a
two-dimensional plot of one or more signals
as a function of time.
• Oscilloscopes display the change of an electrical
signal over time, with voltage and time as the Y-
and X-axes, respectively, on a calibrated scale. The
waveform can then be analyzed for properties such
as amplitude, frequency, rise time, time interval,
distortion, and others. Modern digital instruments
may calculate and display these properties directly.
Originally, calculation of these values required
manually measuring the waveform against the
scales built into the screen of the instrument.
• Oscilloscopes are used in the sciences,
medicine, engineering, automotive and the
telecommunications industry. General-
purpose instruments are used for
maintenance of electronic equipment and
laboratory work. Special-purpose
oscilloscopes may be used for such purposes
as analyzing an automotive ignition system or
to display the waveform of the heartbeat as
an electrocardiogram.
KEYSIGHT DSOX1102G Oscilloscope: 70 MHz,
 The Three Systems
• A basic oscilloscope consists of three different
systems – the vertical system, horizontal system, and
trigger system. Each system contributes to the
oscilloscope’s ability to accurately reconstruct a
signal.

• The front panel of an oscilloscope is divided into

three sections labeled Vertical, Horizontal, and
Trigger. Your oscilloscope may have other sections,
depending on the model and type.
• When using an oscilloscope, you adjust settings in
these areas to accommodate an incoming signal:

• Vertical: This is the attenuation or amplification of the

signal. Use the volts/div control to adjust the
amplitude of the signal to the desired measurement
range.
• Horizontal: This is the time base. Use the sec/div
control to set the amount of time per division
represented horizontally across the screen.
• Trigger: This is the triggering of the
oscilloscope. Use the trigger level to stabilize a
repeating signal, or to trigger on a single
event.
The use of Oscilloscopes
in different modes
 Acquisition Modes

• Acquisition modes control how waveform

points are produced from sample points.
Sample points are the digital values derived
directly from the analog-to-digital converter
(ADC). The sample interval refers to the time
between these sample points.
• Waveform points are the digital values that
are stored in memory and displayed to
construct the waveform. The time-value
difference between waveform points is
referred to as the waveform interval.
Acquisition Menu
• Waveform points are the digital values that are
stored in memory and displayed to construct the
waveform. The time-value difference between
waveform points is referred to as the waveform
interval.
• The sample interval and the waveform interval
may or may not be the same. This fact leads to
the existence of several different acquisition
modes in which one waveform point is
comprised of several sequentially acquired
sample points.
• Additionally, waveform points can be created
from a composite of sample points taken from
multiple acquisitions, which provides another
set of acquisition modes. A description of the
most commonly used acquisition modes
follows.
 Sample Mode
• This is the simplest acquisition mode. The
oscilloscope creates a waveform point by
saving one sample point during each
waveform interval.
 Peak Detect Mode
• The oscilloscope saves the minimum and
maximum value sample points taken during
two waveform intervals and uses these
samples as the two corresponding waveform
points.
• Peak detect mode is particularly useful for
seeing narrow pulses spaced far apart in time,
as shown in
Peak detect mode
 Hi-Res Mode
• Like peak detect, hi-res mode is a way of getting more
information in cases when the ADC can sample faster
than the time base setting requires. In this case,
multiple samples taken within one waveform interval
are averaged together to produce one waveform point.

• The result is a decrease in noise and an improvement

in resolution for low-speed signals. The advantage of
Hi-Res Mode over Average is that Hi-Res Mode can be
used even on a single shot event.
 Envelope Mode
• Envelope mode is similar to peak detect mode.
However, in envelope mode, the minimum and
maximum waveform points from multiple acquisitions
are combined to form a waveform that shows
min/max accumulation over time. Peak detect mode is
usually used to acquire the records that are combined
to form the envelope waveform.
 Average Mode
• In average mode, the oscilloscope saves one
sample point during each waveform interval as
in sample mode. However, waveform points
from consecutive acquisitions are then
averaged together to produce the final
displayed waveform.

• Average mode reduces noise without loss of

bandwidth, but requires a repeating signal.
 Waveform Database Mode
• In waveform database mode, the oscilloscope
accumulates a waveform database that
provides a three-dimensional array of
amplitude, time, and counts.
Signal sources
Advantages of Oscilloscopes (Analog Type)
• It is cheaper compare to digital counterpart.
• It delivers reasonable performance which are
accurate for many lab exercises.
• It does not require ADC, µP (Microprocessor)
and acquisition memory for measurement
purpose.
Advantages of Oscilloscopes (Digital Type)
• It can analyze signal in real time as well as can
analyze large samples of acquired data with
the help of storage memory.
• It can analyze high frequency transients due to
advanced DSP algorithms available.
Disadvantages of Oscilloscopes (Analog Type)

• It can not analyze high frequency sharp rise

time transients.
• As there is no storage memory available, it can
only analyze signal in real time.
• It does not offer all the capabilities as
supported by digital oscilloscope type.
• It requires some amount of training to use it
 Disadvantages of Oscilloscopes
(Digital Type)
• It requires ADC, µP and acquisition memory
for measurement purpose.
• It is costly and cost depends on features
supported in different available models viz.
digital storage oscilloscope, digital phosphor
oscilloscope and digital sampling oscilloscope.
 Digital storage oscilloscope
• The digital storage oscilloscope is of the three
digital oscilloscopes but DSO is the
conventional form of digital oscilloscope. Its
screen is like a computer monitor or TV screen
as it uses raster type screen. By using the
raster screen its helps to display images that
fill the whole screen and it may include text on
the screen.
• First you have to store the waveform in the
digital format to get the raster type display on
screen. As a result of storing the waveform
form digitally it can be processed by the
oscilloscope or by connecting to a computer.
“This enables a high degree of processing to
be achieved, and the required display
provided very easily and often with a very
cheap processing platform.
• It also enables the waveform to be retained
indefinitely, unlike the analogue scopes for
which the waveform could only be stored for a
very limited time.
• The operation of the digital storage oscilloscope
is pretty simple, “The first stage the signal enters
within the scope is the vertical amplifier where
some analogue signal conditioning is
undertaken to scale and position the waveform.
Next this signal is applied to an analogue to
digital converter (ADC).” (www.Radio-
electronics.com).
• The samples are taken at regular intervals. The
sampling rate is important because it
determines the resolution of the signal.
• The samples are taken in per second or MS/s
(mega sample rate). All the samples are stored
within is the oscilloscope as waveform points,
and several samples of waveform make up a
single waveform point. “The overall waveform is
stored as a waveform record and its start is
governed by the trigger, its finish being
determined by the horizontal time base time.”
• The digital storage oscilloscope is an in the
digital format which means there is a signal
processor. With having a signal processor it
helps to process the signal in different ways,
before it passes the display memory and the
display.
(Ian P (2004) oscilloscope types [internet].
Available fromhttp://www.radio-
electronics.com/info/t_and_m/oscilloscope/osci
lloscope_types.php