N2808A Datasheet, PDF (2/13 Pages) Keysight Technologies – PrecisionProbe for the 9000 Series

02 | Keysight | N2808A PrecisionProbe for the 9000 Series - Data Sheet
Keysight’s PrecisionProbe TDT (N2808A) allows
you to characterize and correct your measurement
system quickly and accurately, without adding
expensive equipment.
PrecisionProbe solves measurement challenges by
allowing you to:
–– Characterize the frequency response (both magnitude and
phase) of any input to the 9000 Series without the need for
extra equipment such as a VNA or TDR
–– Quickly and accurately compensate for probe and cable loss,
gaining you valuable margins
–– Correct probing issues such as phase non-linearity, magni-
tude non-flatness, and see the effect of probe loading
–– Quickly gain insight into the impedance/capacitance that
defines your connection
–– Increase the bandwidth of your oscilloscope and probe
Background – PrecisionProbe (Cable correction)
A measurement system is only as good as its weakest link. Users
spend thousands of dollars on test and measurement equipment,
including oscilloscopes, but then ignore the weakest element in
their link, the cable. Oscilloscope vendors now provide methods
to strengthen the weak link with the use of de-embedding
software (Keysight Technologies, Inc. InfiniiSim N5465A
software). However, de-embedding software requires specific
characterization of the cable and the creation of an s-parameter
file. To get the correct characterization you must characterize the
cable using either a TDR or a VNA. Both of these methods provide
characterization and s-parameters, but take time and instrument
knowledge and more investment on test and measurement
equipment.
It is the time, knowledge, and additional equipment that causes
us to simply choose to ignore cable loss, and measurements
taken by the oscilloscope now may be measuring the weakest
link (the cable) and not the device you wish to measure as cable
loss can dominate a measurement. At best you may choose to
characterize only one or two cables, and use that characterization
(s-parameter file) to compensate for of every similar cable you
own, causing the magnification of cable-to-cable variability as
the cables characteristics vary from the “golden” cable.
Figures 1 and 2. Cable loss degrades rise times and causes measurement
non-repeatability. Figure 1 shows the rise time of a signal with a cable
that’s loss is uncharacterized and not compensated. Figure 2 shows the
same measurement with characterization and compensation. Notice
the rise time is >15% faster and the measurement is nearly 50% more
repeatabile.