Measuring Resistance; Connecting Analog Output Signals - National Instruments BNC-2120 Installation Manual

For more information on thermocouples and CJC, refer to the Developer Zone document, Taking
Thermocouple Temperature Measurements, by going to
.
rdtttm

Measuring Resistance

You can measure resistance with the analog input screw terminals on the BNC-2120. Figure 4 is a
schematic representation of how the BNC-2120 measures resistance.
RES+ is internally connected to AI 3 and V
10 kΩ resistor between AI 11 and AI GND.
When connecting signals to the screw terminals, use 28–16 AWG wire with the insulation stripped
to 0.28 in.
Complete the following steps to measure resistance.
1. Move the RES/BNC switch above the AI 3 BNC to the RES position.
2. Configure your software to measure AI 3 and AI 11 in referenced single-ended (RSE) mode.
3. Connect the resistor to the RES+ and RES– screw terminals.
You can measure resistors with values ranging from 100 Ω to 1 MΩ.
4. Measure V
5. With these measurements, calculate the resistor value using the following formula:

Connecting Analog Output Signals

Use the AO <0..1> BNC connectors on the BNC-2120 front panel to connect analog output signals to
your DAQ device.
Refer to your DAQ device documentation for information about the use of these signals.
1
When using the BNC-2120 with Connector 1 of NI 6229/6259/6289 devices, the AO <0..1> BNCs on the BNC-2120 map to
the AO <2..3> channels on the M Series device.
© National Instruments Corporation
Screw
Terminals
User Resistor
Figure 4. Measuring Resistance on the BNC-2120
on AI 3 and the voltage drop across the internal 10 kΩ resistor on AI 11.
CC
Resistor Value
1
The number of connectors you use depends on your DAQ device and application.
ni.com/info
BNC-2120
V
CC
RES+
AI GND
AI SENSE
RES–
10 kΩ
0.5%
AI
. RES– is internally connected to AI 11. There is also a
CC
V V
–
AI 3 AI 11
= -------------------------------------- -
⁄ (
V 10 kΩ
AI 11
7
and entering the info code
AI 3
AI 11
)
BNC-2120 Installation Guide