Connecting Ai Signals On The Usb-6215/6218 Devices; Differential Measurements; Differential Pairs - National Instruments NI USB-621x User Manual

Connecting AI Signals on the
USB-6215/6218 Devices
Note You must always connect AI GND to a local ground signal in your system using a
low impedance connection. If you leave AI GND unconnected, you cannot ensure that
AI <0..31> are within 10 V of AI GND, and your measurement may be unreliable.

Differential Measurements

Differential Pairs

© National Instruments Corporation
You can connect the USB-6215/6218 directly to a variety of devices and
other signal sources. Make sure the devices you connect to the
USB-6215/6218 are compatible with the input specifications of the
module.
When connecting various sources to the USB-6215/6218, you can use
differential, single-ended, or a combination of single-ended and differential
connections. Refer to Figures 6-1, 6-2, and 6-3 for diagrams of each
connection type.
To attain more accurate measurements and less noise, use a differential
measurement configuration. A differential measurement configuration
requires two inputs for each measurement.
Table 6-1 the signal pairs that are valid for differential connection
configurations with the USB-6215/6218.
Channel
0
1
2
Table 6-1. I/O Connector Signals
Signal +
AI 0
AI 1
AI 2
6-1
6
Signal –
AI 8
AI 9
AI 10
NI USB-621x User Manual