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3.2.5 The 1689-9602 Extender Cable
with bnc-to-Banana-Plug
Adaptors
To connect to DUT's that are multi-terminal, physi-
cally large, or otherwise unsuited for remote test
fixtures, connect bnc-to-banana-plug adaptors to the
extender cable (See Figure 3-12). This is particularly
convenient for DUT's with binding posts. This acces-
sory cable (1689-9602), as well as the Pomona 1894
and 4684 adaptors, are available from IET Labs. Also
see 7000-04 Alligator Clip Leads.
Figure 3-12: 1689-9602 Extender Cable with
bnc-to-banana-plug adapters
To use this cable with the adaptors, proceed as
follows:
1. Connect 1689-9602 bnc cable to the 1693
Digibridge as specified in Table 3-1 on page 19.
2. Connect the set of four bnc-to-banana-plug
adaptors to the free ends of the cables. One
of these adaptors has a "pigtail" for connect-
ing GUARD.
3. Zero the Digibridge. (See Section 3.1.3 on
page 14.)
4. Connect the banana plugs (and GUARD, if
appropriate) to the DUT.
CAUTION
Avoid contact between the shells
o f b n c c o n n e c t o rs . O t h e r w i s e ,
m e a s u r e m e n t s a t h i g h t e s t
frequencies may have errors that
result from the changing mutual
inductances between cable shields.
Operation
3.2.6 The Effects of Cable and
Fixture Capacitances
It is important to use very low-capacitance shielded
wire for cables, not only for accuracy, but also to
minimize resonance effects in the measurement of
large inductance at high frequency.
The Capacitance that are Most Liable to Affect
Accuracy. Any test fixture extension cable adds a
bit of capacitance in parallel with the DUT (because
shielding of the leads is imperfect) and more between
each terminal and ground. The zeroing process
(Section 3.1.3) will compensate fully for the capaci-
tances between cables in any normal test setup.
However, capacitance between ground and the "low"
connections at the DUT (C from ground to IL and C
from ground to PL , in parallel, designated Csn) can
affect measurement accuracy of very-high-impedance
DUTs at high frequencies.
Zeroing. Be sure to repeat either the entire power-up
procedure or at least the open-circuit and short-circuit
zeroing procedure after any change in test fixtures or
their cable connections.
Calculating the Capacitance Loading Error. The error
due to this capacitance Csn is designated Ald ("ad-
ditional error due to loading"). The magnitude of Ald
can be calculated so that you know how significant
it is and so that measurements can be corrected if
desired. Refer to paragraph 3.6.7.
1693 RLC Digibridge
21
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