National Instruments PXI Terminal Block NI TB-2708 - Manual (Page 6)

NI TB-2708 Installation Guide 6 ni.com
Measuring Floating Signals
You can use the TB-2708 to measure floating and ground-referenced
analog input signals. To measure floating signal sources, move the switch
located under the rubber-sealed door on the enclosure cover for the AI
channel you are using to the ON (floating source) switch position. In the
floating source switch position, the amplifier negative terminal connects to
ground through a 5 k
Ω resistor in parallel with a 0.1 μF capacitor. Table 2
shows the TB-2708 switch configuration options.
Measuring Ground-Referenced Signals
It is possible to set the switch on the TB-2708 to either the floating or
ground-referenced source position to measure ground-referenced signals.
However, for best results, use the OFF (ground-referenced source) switch
position to avoid ground loops. Refer to the S Series User Manual for more
information on measuring floating and ground-referenced signals.
Table 2. Configuration Summary
TB-2708 Switch
Configuration
Signal Source Types for S Series Devices
Floating Source Ground-Referenced Source
Floating Source
Ground-
Referenced Source
+
–
Signal
Source
TB-2708
DAQ Device
(Differential Input
Mode)
AI GND
+
–
Recommended
+
–
Signal
Source
TB-2708
DAQ Device
(Differential Input
Mode)
AI GND
+
–
Not Recommended
+
–
Signal
Source
TB-2708
Improper Configuration
DAQ Device
(Differential Input
Mode)
+
–
AI GND
+
–
Signal
Source
TB-2708
DAQ Device
(Differential Input
Mode)
AI GND
+
–
Recommended