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2.5.4 General instrument connections
The following paragraphs discuss connecting the Model
7174A to various general classes of instrumentation such as
DMMs, electrometers, sources, and source/measure units.
Because these configurations are generic in nature, some
modification of the connecting schemes may be necessary
for your particular instrumentation. Also, special cables or
adapters may be necessary. In all cases, 3-lug triax cables
must be used to make the connections.
WARNING
Do not use coaxial cables and adapters
because hazardous voltage from guard
sources may be present on the cable
shields.
Figure 2-5 shows the general instrument connections for the
discussions below. Note that DUT guarding or shielding are
not included here; see Figures 2-22 and 2-23 for shielding
and guarding information. As shown, all figure assume
instruments are connected to rows, and the DUT is con-
nected to columns.
DMM connections
General DMM connections are shown in Figure 2-5 (A), (B),
and (C). Floating connections are shown in (A) with LO and
HI routed to two separate jacks on the Model 7174A. The
common LO connections in (Figure 2-5B) should be used
only for non-critical applications because the performance of
the GUARD pathway is not specified.
WARNING
Hazardous voltage from other guard
sources may be present on LO or the
DUT if other crosspoints are closed.
4-wire DMM connections are shown in Figure 2-5(C). In this
case, a total of four jacks are required; HI, LO, SENSE HI,
and SENSE LO.
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Electrometer connections
Typical electrometer connections are shown in Figure 2-5(D)
through (G). The unguarded volts connections in (D) show
the HI signal path routed through one jack, and the LO path
goes through the other connector. Both GUARD pathways
are connected to electrometer LO. For guarded voltage (E),
Model 7174A GUARD is connected to electrometer
GUARD.
The connections for electrometer fast amps and resistance
measurements are shown in Figure 2-5(F) and (G). These
configurations are essentially the same as those discussed
above. For the case of fast amps, both GUARD paths are
connected to electrometer LO, while in the case of guarded
resistance, one GUARD path is connected to electrometer
GUARD, and the other GUARD path is connected to elec-
trometer LO.
Source connections
Voltage and current source connections are shown in Figure
2-5(H) through (J). The HI and LO paths of the voltage
source (H) are routed through two jacks, with both card
GUARD pathways connected to voltage source LO. For the
unguarded current source connections (I), card GUARD is
again connected to source LO, with source HI and LO routed
through two pathways. In the case of the guarded current
source in (J), card GUARD of the HI signal path is connected
to source GUARD, and the other GUARD path is connected
to source LO.
Source/measure unit connections
Figure 2-5(K) shows typical connections for a source/mea-
sure unit (SMU). In this instance, a remote-sensing type of a
SMU is shown, requiring a total of four signal pathways to
the DUT. For critical measurements, both source and sense
HI pathways would be guarded as shown, with two of the
four card GUARD pathways connected to SMU GUARD
terminals. As with other instrument connections, the LO card
GUARD pathways are connected to SMU LO terminals.
Operation
2-5
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