BNC-2120 Installation Guide
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© National Instruments
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7
Measuring Ground-Referenced Signals
To measure ground-referenced signals, move the switch below the BNC connector for the
AI channel you are using to the GS position. Using the ground-referenced source switch position
avoids ground loops, as shown in Figure 3. Refer to your DAQ device documentation for more
information about measuring ground-referenced signals.
Figure 3.
Measuring a Ground-Referenced Signal Source
AI GND and AI SENSE signals are located at the analog input screw terminals of the
BNC-2120. When connecting signals to the screw terminals, use 28–16 AWG wire with the
insulation stripped to 0.28 in.
Measuring Temperature
You can measure temperature on the BNC-2120 with the temperature reference and
thermocouple connector.
To use the integrated circuit (IC) temperature reference on the BNC-2120, move the BNC/Temp.
Ref. switch above the AI 0 BNC to Temp. Ref. The integrated circuit (IC) temperature reference
provides built-in cold-junction compensation (CJC) through software. The IC sensor voltage is
linearly proportional to the sensor temperature where:
°C = Volts
×
100
The sensor is accurate to ±1.5
°
C.
To use the thermocouple on the BNC-2120, move the BNC/Thermocouple switch above the AI 1
BNC to Thermocouple. You can connect any type of thermocouple with a two-prong miniature
or subminiature male connector to the thermocouple connector.
For more information on thermocouples and CJC, refer to the Developer Zone document,
Taking
Thermocouple Temperature Measurements
, by going to
ni.com/info
and entering the Info
Code
rdtttm
.
+
–
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
G
S
G
S
Mode
0.1
μ
F
