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. Using a NI-DAQmx Global Virtual Channel, you can configure a thermocouple measurement without any programming. You can use NI MAX to quickly verify the accuracy of your measurement system setup. Refer to Figure 3 for an illustration of a typical shielding configuration.įigure 3. Connecting a Shielded Thermocouple The shield grounding methodology can vary depending on the application. If you are using a floating thermocouple or a thermocouple within ☑.2 V of earth ground, connect COM and the shield to earth ground. A common-mode voltage reference is a voltage that is within ☑.2 V of the common-mode voltage of the thermocouple. 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. If you are unsure which of the thermocouple leads is positive and which is negative, check the thermocouple documentation or the thermocouple wire spool. Connect the positive lead of the thermocouple to the TC+ terminal and the negative lead of the thermocouple to the TC– terminal.

The connection diagram in Figure 2 indicates which pins on your DAQ device should be wired according to the physical channel you selected.

Each thermocouple wire has a positive lead and a negative lead.

Set up a pid controller in labview vi