61 / 84
so the longer the cables the bigger
the error.
The result would be considered to
be excellent even if the result were
further from the nominal, in order
to account for these additional
tolerances. It is clear that the Picotest
J2102A common mode transformer
and a preamp are indispensable when
it comes to getting the most accuracy
during PDN measurement.
Figure 5 Impedance measurement of the 2mΩ resistor, using Port 1
and Port 2, with and without the common mode coaxial transformer
on the Keysight E5061B. The unique GP ports don’t require the
transformer, but are limited to 30MHz
Figure 5 A DC measurement
is made using precision, low
noise 6.5 Digit DMMs (Picotest
M3500A) to obtain a second
measurement for correlation.
The power supply does not have
current programming, which is
the reason the current is set to an
odd number. The two channels of
the power supply are connected
in parallel and both are in current
limit for this measurement.
Figure 6 - Noise floor in Ohms on
the Bode 100 using the J2102A
and the J2180A preamplifier
included
Figure 4, The Bode 100
measurement of the 250uOhm
resistor shown in Figure 1. The
measured resistance and ESL are
shown
New-Tech Magazine Europe l 61