National Instruments NI 9478 - page 11

© National Instruments Corp. 11 NI 9478 Operating Instructions and Specifications
You can reduce the effective length of the cable by adding a
capacitor close to the NI 9478 across the power supply leads and
adding a diode from the digital output line to the Vsup pin line.
National Instruments recommends that you use a capacitor with a
capacitance of at least 20 μF. In this case, the effective length of the
cable is the distance from the output pin, through the new diode,
through the capacitor, and back to the COM pin, as shown in
Figure5.
Figure 5. Cable Length of the NI 9478 with a Capacitor and Diode
NI 9478COM
Vsup
DO
+
–
External
Power
Supply
Cable
Length
Load
Cable
Clamp