National Instruments sbRIO-9605 - Page 33

© National Instruments 33 NI sbRIO-960x/962x/963x OEM Instructions & Specifications
Figure 25. Differential Connections for Floating Signal Sources with
Single Bias Resistor
You can fully balance the signal path by connecting another resistor of
the same value between the positive input and AI GND, as shown in
Figure 26. This fully balanced configuration offers slightly better noise
rejection, but has the disadvantage of loading the source down with the
series combination (sum) of the two resistors. If, for example, the source
impedance is 2 kΩ and each of the two resistors is 100 kΩ, the resistors
load down the source with 200 kΩ and produce a –1% gain error.
–
+
R is about
100 times
source
impedance
of sensor
AI GND
R
V
s
Floating
Signal
Source
AI+
AI–