23 |
The cable connecting the signal to the acquisition
device
exceeds 3 meters
The input signal requires a separate reference location or a return signal
There is obvious noise in the environment of the signal wire
+
-
Differential connection mode can reduce noise interference and improve the common-mode
suppression of the acquisition
device
. Differential connection allows the input signal to float
within the common-mode operating range of the instrument amplifier.
Figure 3.7 shows how to use differential mode to connect the grounded signal source
USB-3200
AI+
AI-
+
Vcm
-
Figure 3.7 grounded signal source DIFF input
Use a non-grounded reference single-ended mode (NRSE) connection
When all of the following conditions are true, you can connect the float signal using a
non-grounded reference single-ended mode:
The input signal voltage is higher than 1V
The cable connecting the signal to the acquisition
device
is less than 3 meters
long
The input signal shares a reference point whose voltage is not AI-GND.
If the signal does not meet the above conditions, it is recommended to use a differential mode
connection to ensure better signal integrity. In single-ended mode, the electrostatic noise and
electromagnetic noise of the coupled input signal connection are more than that in the difference
mode.
Figure 3.8 shows the grounded signal source (NRSE) connection in non-grounded reference
single-ended mode.