©
National Instruments Corp.
11
NI 9478 Operating Instructions and Specifications
Yo
u
can red
u
ce the effective length of the cable by adding a
capacitor close to the NI 9478 across the power s
u
pply leads and
adding a diode from the digital o
u
tp
u
t line to the V
s
u
p
pin line.
National Instr
u
ments recommends that yo
u
u
se a capacitor with a
capacitance of at least 20
μ
F. In this case, the effective length of the
cable is the distance from the o
u
tp
u
t pin, thro
u
gh the new diode,
thro
u
gh the capacitor, and back to the COM pin, as shown in
Fig
u
re 5.
Figure 5.
Cable Length of the NI 9478 with a Capacitor and Diode
NI 947
8
COM
V
su
p
DO
+
–
External
Power
S
u
pply
Cable
Length
Load
Cable
Clamp
