Before connecting any signals, locate your device pinout.
The following terminal types correspond with thermocouple measurements:
The next step is to physically connect the thermocouple to your DAQ device.
Each thermocouple wire has a positive lead and a negative lead. The connection diagram in Figure 2 indicates which pins on your DAQ device should be wired according to the physical channel you selected. Connect the positive lead of the thermocouple to the TC+ terminal and the negative lead of the thermocouple to the TC– terminal. If you are unsure which of the thermocouple leads is positive and which is negative, check the thermocouple documentation or the thermocouple wire spool.If you are using a shielded thermocouple, connect the COM terminal of your device to the shield and the shield to a common-mode voltage reference of the thermocouple. A common-mode voltage reference is a voltage that is within ±1.2 V of the common-mode voltage of the thermocouple. If you are using a floating thermocouple or a thermocouple within ±1.2 V of earth ground, connect COM and the shield to earth ground. The shield grounding methodology can vary depending on the application. Refer to Figure 3 for an illustration of a typical shielding configuration.
Figure 3. Connecting a Shielded Thermocouple
You can use NI MAX to quickly verify the accuracy of your measurement system setup. Using a NI-DAQmx Global Virtual Channel, you can configure a thermocouple measurement without any programming. A virtual channel is a concept of the NI-DAQmx driver architecture used to represent a collection of device property settings that can include a name, a physical channel, input terminal connections, the type of measurement or generation, and scaling information.
Follow these steps to begin:
With NI-DAQmx global virtual channels, you can preview your measurements.
The following example code is provided in the LabVIEW Example Finder under Hardware Input and Output» DAQmx» Analog Input» Thermocouple - SW-Timed Input. vi. (Note that this example file may have a different name or filepath depending on your LabVIEW version.)The front panel of this example allows the user to:
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