Chapter 5 Connecting AI Signals on the USB-6210/6211 Devices

Using Differential Connections for Ground-Referenced Signal Sources

Figure 5-7shows how to connect a ground-referenced signal source to the

USB-6210/6211 device configured in DIFF mode.

 

 

AI+

 

 

 

Ground-

+

 

 

 

 

Referenced

 

Instrumentation

Signal

Vs

 

+

Amplifier

Source

–

 

 

 

 

 

 

AI–

PGIA

 

+

 

 

 

 

Measured

 

 

–

 

Vm

 

 

 

 

Voltage

Common-

 

 

 

 

+

 

 

 

–

Mode

 

 

 

 

 

 

 

Vcm

 

 

 

 

Noise and

 

 

 

 

Ground

–

 

 

 

 

 

 

 

 

 

Potential

 

 

 

 

 

 

 

Input Multiplexers

 

 

 

 

 

AI SENSE

 

 

 

 

 

AI GND

 

 

 

I/O Connector

 

 

 

 

 

 

M Series Device Configured in DIFF Mode

Figure 5-7.Differential Connections for Ground-Referenced Signal Sources

With this type of connection, the NI-PGIA rejects both the common-mode noise in the signal and the ground potential difference between the signal source and the device ground, shown as Vcm in the figure.

AI+ and AI– must both remain within ±11 V of AI GND.