National Instruments NI 6238 - Manual (Page 30)

Chapter 4 Analog Input
NI 6238/6239 User Manual 4-4 ni.com
Figure 4-2. Analog Current Input Connection Method 1
Method 2
Method 2, shown in Figure 4-3, ties the AI – input to AI GND. When
measuring current up to 20 mA, this type of connection ensures that the
voltage level on both the positive and negative side are within the
common-mode input range for NI 6238/6239 devices.
Figure 4-3. Analog Current Input Connection Method 2
+
–
AI +
AI –
Isolation
Barrier
AI GND
V
AI GND
+
–
+
–
AI +
AI –
Isolation
Barrier
AI GND