National Instruments SCB-68A - Adding Components for Highpass Filtering on Analog Input Signals

2-30 | ni.com
Chapter 2 Analog Input and Temperature Sensor Measurements
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 Highpass Filtering on Analog
Input Signals
Using the circuit shown in Figure 2-27, you can use a two-component circuit to build a simple
RC filter with an analog input.
• Differential analog input highpass filter—To build a differential highpass filter, add the
resistor to position E and the capacitor to position F, as shown in Figure 2-28. 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 2-28. SCB-68A Circuit Diagram for Differential Analog Input Highpass Filter
• Single-ended analog input highpass filter—To build a single-ended highpass filter, refer
to Figure 2-29. Add the resistor to position B or D, depending on the AI channel you are
using. Add the capacitor to position F or G, 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 resistor in the F and G positions. You must
remove the resistor to use the position.
AIi
AIi+8
y
SCx
E
A
F
G
B
C
D
+
+
+
+
5 V AI GND
+
5 V AI GND
AI i
AI i
+
8