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Application Note
Make Safe and Accurate
Measurements with High-
Voltage Probes
Moreover, the P5100 offers the
rugged physical construction
needed for power measure-
ments. Its special retractable
hook tip provides a positive
connection on test points up
to 6.5 mm in diameter.
The Unit-Under-Test
The Unit-Under-Test (UUT)
is a control board within a
"cell" of a Robicon Motor
Drive. Robicon, Inc. is a lead-
ing manufacturer of conven-
tional and harmonic drives
for high-power AC electric
motors used in air condition-
ing systems, oilfield pumping
TDS 220 Digital Real-Time Oscilloscope (top); P5100 High-Voltage
Probe (right). equipment, etc. A system
may consist of many modular
power cells. Each must pass
rigorous manufacturing qual-
ity tests to ensure not only
customer satisfaction, but
also customer safety.
High-voltage measurements conventional DSO equipped
The cells use IGBT (Insulated
with a general-purpose oscil- with a 10X passive probe. For
Gate Bipolar Transistor)
loscope aren't complex or the TDS 220, the maximum
devices to deliver power to
esoteric, but they do call for input voltage is 300 V RMS or
the load. These IGBTs are
tools and methods different 424 V DC + peak AC when
controlled by a logic board
from those used in everyday using a standard P6112 Probe.
that is integral to the cell; the
testing of logic and low- Most measurements require digital ICs on this board are
power analog circuits. High- the viewed signal to be posi- powered by low-voltage sup-
voltage measurements are tioned entirely within the plies derived from the sys-
important for testing switch- eight vertical divisions of the tem's transformer secondary
ing power supplies, motor scope graticule. Signals voltage. The conversion from
controllers, power distribu- exceeding this level must be line input level to the
tion systems, and more. This attenuated to fit within the