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Keysight Technologies
U1881A and U1882A
Measurement Application for InfiniiVision
and Infiniium Oscilloscopes
Data Sheet
Fast, automatic and reliable characterization of
switching mode power devices
Today's power supply designers are facing an increasing number of constraints in the
development of high-efficiency, low-cost power supplies. Cost-effective solutions used
to be the designer's key target. Today, rising energy costs bring power supply efficiency
to the forefront. Additionally, other constraints such as design compactness, migration
to digital control, tighter voltage tolerances, and regulations for power quality and EMI
force the need for quick and reliable power supply testing. Increasing design constraints
translate into more time dedicated to power device measurement and analysis for
today's power supply designers.
In spite of the increasing analysis capability offered by many oscilloscopes over recent
years, it is not uncommon to see designers perform measurements and characterization
manually. These measurements typically take a considerable amount of time to capture,
analyze, and report.
Figure 1. Power measurement application running on a Keysight 8000 Series
oscilloscope provides a single-box solution for testing switching mode
power supply characteristics
03 | Keysight | U1881A and U1882A Measurement Application for InfiniiVision and Infiniium Oscilloscopes - Data Sheet
Full-featured measurements and automatic reporting of switch-
ing mode power supply (SMPS) characteristics
Now you can skip the time-consuming manual measurements Keysight's power measurement application offers seven
when you are characterizing your power devices. The U1881A modules to help you characterize your devices (power
and U1882A power measurement application for device analysis, input line analysis, output analysis, turn on/off
Keysight Technologies, Inc. oscilloscopes provide a full suite analysis, transient analysis, modulation analysis) in addition to
of power measurements that run directly on an Infiniium 8000 deskew and report generation. Each module contains relevant
and 9000 Series oscilloscope or on a separate PC for use with measurement and setup selections for easy repeatability.
InfiniiVision 3000 X-Series and 7000 Series oscilloscopes.
Modules Measurements
Deskew Automatic deskew for voltage and current probes
Power device analysis Switching loss
Safe operating area (SOA) with SOA mask editing
Dynamic ON resistance
dI/dt
dV/dt
Input line analysis Power factor (real power/apparent power)
Real power
Apparent power
Reactive power
Crest factor
Precompliance test to IEC61000-3-2 std A, B, C, D and RTCA DO-160E
Inrush current analysis Inrush current
Output analysis Output voltage ripple
Turn on/off analysis Turn on time
Turn off time
Transient analysis Transient load response
Modulation analysis Pulse width versus time plot
Duty cycle versus time plot
Period versus time plot
Frequency versus time plot
Report generation Report generation
04 | Keysight | U1881A and U1882A Measurement Application for InfiniiVision and Infiniium Oscilloscopes - Data Sheet
Auto deskewing and U1880A deskew fixture
A power measurement is simply a point-by-point multiplication of application, you can use the saved deskew values or perform
the voltage and current waveforms measured by the voltage and the deskewing again.
current probes. To make accurate power measurement and
calculation, it is extremely important to equalize the time delay The deskew accuracy is a function of the electrical
between the voltage and current probes using a procedure characteristics of the voltage and current probes as well as the
known as deskewing. This step is critically important since a risetime of the signal under test. In general, higher bandwidth
small offset in the timing of the voltage and current traces can probes will allow for better risetime fidelity and better deskew
cause a large error in the instantaneous power reading. To resolution. Keysight's N2790A to N2793A differential probes
deskew a pair of probes, drive both voltage and current probes are recommended for most applications.
with the same pulse signal using the U1880A deskew fixture.
With only a single click on the menu, deskewing is automatically The U1880A deskew fixture is recommended for use with the
performed and its values are saved in the power measurement following voltage and current probe combinations given various
software, so the next time you launch the power measurement test signal risetime characteristics.
Figure 2. Deskew dialog Figure 3. Deskew fixture
05 | Keysight | U1881A and U1882A Measurement Application for InfiniiVision and Infiniium Oscilloscopes - Data Sheet
Power device analysis
The switching loss in a power supply determines its
efficiency. You can easily characterize instantaneous power loss
and conduction power loss at the switching device over a
designated switching cycle. The dynamic ON resistance
measurement shows you power loss while the power transistor is
conducting.
To determine the reliability of the power supply it is very
important to measure the power loss during dynamic load
changes and to observe the SOA (safe operating area) plot. Using
deep acquisition memory on the scope with the SOA plot, you
can easily identify improper power transistor behavior.
Figure 4. Power device analysis results are displayed both graphically and in
a tabular, "lister" format
Input line analysis
Power supply designers need to characterize the line power
for power quality, harmonics and conducted emissions under
different operating conditions of the power supply. Some of the
implicit measurements are real power, apparent power, reactive
power, power and crest factor, and graphical display of
harmonics with respect to standards such as IEC 61000-3-2
(Class A, B, C, D) and RTCA DO 160E. By using a current probe
and the power measurement software (equipped with an FFT
math function), you can measure conducted power line
harmonics.
Figure 5. Input line analysis results
06 | Keysight | U1881A and U1882A Measurement Application for InfiniiVision and Infiniium Oscilloscopes - Data Sheet
Modulation analysis
Modulation analysis allows you to quickly see the on-time and
off-time information of the PWM signal, which is difficult to
visualize because the information bandwidth is much lower than
the pulse switching frequency. Plotting the embedded variation
of on time or off time in the PWM signal over a long period of
time can reveal the control loop response of the feedback loop
system. This measurement performs data trending on the
switching variation of the acquired waveform in the following
formats: