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BNC-2120 Installation Guide
Connecting Differential Analog Input Signals
Use the BNC-2120 BNC connectors on the front panel to connect AI <0..7> signals to your
DAQ device. The BNC-2120 is
only
intended for differential analog input signals. The number
of connectors you use depends on your DAQ device and application. Complete the following
steps to measure a differential (DIFF) analog input signal.
1.
Connect the BNC cable to one of the AI <0..7> BNC connectors on the front panel.
1
2.
If you are using AI 0, move the BNC/Temp. Ref. switch to the BNC position.
If you are using AI 1, move the BNC/Thermocouple switch to the BNC position.
If you are using AI 3, move the RES/BNC switch to the BNC position.
3.
Configure your software to measure the channel differentially.
4.
Move the FS/GS switch to the applicable position, depending on whether you are
measuring a floating source (FS) or ground-referenced source (GS) analog input signal.
Refer to the
and
Measuring Ground-Referenced Signals
sections for more information about these signal sources.
Measuring Floating Signals
To measure floating signal sources, move the corresponding switch below the BNC connector
to the FS position. In the floating source switch position, the DAQ device’s amplifier negative
terminal connects to ground through a 4.99 k
Ω
resistor, as shown in Figure 2. Refer to your
DAQ device documentation for more information about measuring floating signals.
Figure 2.
Measuring a Floating Signal Source
1
When using the BNC-2120 with Connector 1 of two connector M/X Series devices, the AI <0..7> BNCs
on the BNC-2120 map to the AI <16..23> channels on the device.
+
–
S
ign
a
l
S
o
u
rce
BNC-2120
DAQ Device
(Differenti
a
l Inp
u
t Mode)
AI GND
+
–
4.99 k
Ω
F
S
F
S
Mode
0.1
μ
F
