Wiring And Noise Reduction Methods; Separating Digital And Analog Scp Signals; Wiring And Noise Reduction - VXI VT1422A User Manual

Wiring and Noise Reduction Methods

Separating Digital and Analog SCP Signals

Analog Input and
Digital Input and
Appendix E
Signals with very fast rise time can cause interference with nearby signal
paths. This is called cross-talk. Digital signals present this fast rise-time
situation. Digital I/O signal lines that are very close to analog input signal
lines can inject noise into them.
To minimize cross-talk, maximize the distance between analog input and
digital I/O signal lines. By installing analog input SCPs in positions 0
through 3 and digital I/O SCPs in positions 4 through 7, these types of
signals are kept separated by the width of the VT1422A module. The signals
are further isolated because they remain separated on the connector module
as well. Note that in Figure E-1, even though only seven of the eight SCP
positions are filled, the SCPs present are not installed contiguously, but are
arranged to provide as much digital/analog separation as possible.
If it is necessary to mix analog input and digital I/O SCPs on the same side,
the following suggestions will help provide quieter analog measurements.
•
Use analog input SCPs that provide filtering on the mixed side.
•
Route only high level analog signals to the mixed side.
SCP Pos 0
Output
SCP Pos 7
VT1533A
Digital I/O
Output
Figure E-1. Separating Analog and Digital Signals
SCP Pos 1 SCP Pos 2 SCP Pos 3
SCP Pos 6 SCP Pos 5 SCP Pos 4
VT1534A empty VT1531A
PWM, Freq & Voltage DAC
Totalizer
Wiring and Noise Reduction Methods
Appendix E
483