Datasheet

www.tektronix.com/power 5
Power Supply Measurement and Analysis with Bench Oscilloscopes
Figure 7. Tektronix Deskew Pulse Generator and Deskew Fixture.
Figure 9. Tektronix TCP0030 AC/DC Current Probe with Degauss/AutoZero.
Figure 8. Manual Removal of Timing Skew between Voltage and Current Probes.
Selecting “Set all deskews to recommended values” accounts
for the probes’ nominal propagation delay differences which
will come very close to deskewing them correctly, but still
may not precisely align the waveforms. In order to precisely
align the waveforms for greatest measurement accuracy, the
TEK-DPG (Deskew Pulse Generator) and deskew fixture are
required.
The TEK-DPG provides a source signal to the Power
Measurement Deskew Fixture (Tektronix part number
067-1686-XX) as shown in Figure 7. With the probes
connected to the deskew fixture, the “Actual Deskew” may
be manually dialed-in to change the deskew value to precisely
align the waveforms. Figure 8 depicts that the TDP1000
probe’s “Actual Deskew” value has been adjusted 680 ps from
6.5 ns to 7.18 ns for maximum accuracy.
Eliminating Probe Offset
Differential probes tend to have a slight voltage offset. This
offset can affect accuracy and must be removed before
proceeding with measurements. Most differential voltage
probes have built-in DC offset adjustment controls, which
makes offset removal a relatively simple procedure.
Current probes may also need to be adjusted before making
measurements. Current probe offset adjustments are made
by nulling the DC balance to a mean value of 0 amperes
or as close as possible. TekVPI-enabled probes, such as
the TCP0030A AC/DC current probe, have an automatic
Degauss/AutoZero procedure built in that’s as simple as
pressing a button on the probe compensation box.