National Instruments Data Acquisition Device E Series User Manual
Page 56
Chapter 2
Analog Input
© National Instruments Corporation
2-23
Therefore, half as many DIFF channel pairs are available compared to
individual channels.
Use DIFF input connections for any channel that meets any of the following
conditions:
•
The input signal is low-level (less than 1 V).
•
The leads connecting the signal to the device are greater than 3 m
(10 ft.).
•
The input signal requires a separate ground-reference point or return
signal.
•
The signal leads travel through noisy environments.
DIFF signal connections reduce noise pickup and increase common-mode
noise rejection. DIFF signal connections also allow input signals to float
within the common-mode limits of the PGIA.
Differential Connections for Ground-Referenced Signal Sources
Figure 2-9 shows how to connect a ground-referenced signal source to a
channel on the device configured in DIFF mode.
Figure 2-9. Differential Connections for Ground-Referenced Signal Sources
E Series Device Configured in DIFF Mode
PGIA
–
+
–
+
–
+
–
+
Vcm
Vs
Ground-
Referenced
Signal
Source
Common-
Mode
Noise and
Ground
Potential
AI GND
AI SENSE
Input Multiplexers
Vm
Measured
Voltage
Instrumentation
Amplifier
AI +
AI –
I/O Connector