© National Instruments
|
2-25
Choose a capacitor that has the following suggested characteristics:
•
AXL or RDL package
•
Tolerance of 20%
•
Maximum voltage of at least 25 V
Adding Components for Lowpass Filters on Analog
Input Signals
Using the circuit shown in Figure 2-21, you can use a two-component circuit to build a simple
RC filter with analog input. You can build a lowpass filter for the following analog input modes:
•
Differential analog input lowpass filter
—To build a differential lowpass filter, refer to
Figure 2-22. Add the resistor to position F and the capacitor to position E. Refer to
Table 2-1 for component positions for all analog input channels.
The SCB-68A ships with a surface mount 0
Ω
resistor in the F position. You
must
remove
the resistor to use the position.
Figure 2-22.
SCB-68A Circuit Diagram for Differential Analog Input Lowpass Filter
•
Single-ended analog input lowpass filter
—To build a single-ended lowpass filter, refer to
Figure 2-23. Add the resistor to position F or G, depending on the AI channel you are using.
Add the capacitor to position B or D, depending on the AI channel you are using. Refer to
Table 2-1 for component positions for all analog input channels.
The SCB-68A ships with a surface mount 0
Ω
resistors in the F and G positions. You
must
remove the resistor to use the position.
AI
i
AI
i
+
8
y
S
C
x
E
A
F
G
B
C
D
+
+
+
+ 5 V
AI GND
+ 5 V
AI GND
AI
i
AI
i
+
8
