Example 2: Logging a Temperature Signal with Start and Stop Conditions

The following procedure describes how to log a temperature signal from an NI-DAQmx device. This example uses the project you created in Example 1: Logging a Temperature Signal.

Complete the following steps to configure LabVIEW SignalExpress to begin logging the temperature signal when the signal rises above 75 degrees Fahrenheit and to stop logging the signal when the signal falls back below 75 degrees Fahrenheit.

1. Open the project you saved in Example 1: Logging a Temperature Signal.
2. Select View»Recording Options to display the Recording Options tab. The Category list displays the pages of the tab you can use to configure logging operations. The Signal Selection page is selected by default because you must select a signal to log before you can configure logging.
3. The Signal selection list on the Signal Selection page displays the signals in the project that you can log. In the Channel Name column, expand Thermocouple and place a checkmark in the Record checkbox for channel Dev1/ai0. The Record While Running button replaces the Record button in the toolbar.
4. In the Category list, select Start Conditions to display the Start Conditions page.
5. Click the Add button to add a new start condition to the Start condition list and display additional configuration options.
6. Verify that Signal trigger appears in the Condition type pull-down menu, Thermocouple - Dev1_ai0 appears in the Signal pull-down menu, and Rising slope appears in the Trigger type pull-down menu.
7. Enter 75 in the Trigger value field to specify for logging to start when the signal from the thermocouple crosses 75 with a rising slope, or exceeds 75 degrees Fahrenheit.
8. In the Category list, select Stop Conditions to display the Stop Conditions page.
9. Click the Add button to add a new stop condition to the Stop condition list and display additional configuration options.
10. Select Signal trigger from the Condition type pull-down menu.
11. Verify that Thermocouple - Dev1_ai0 appears in the Signal pull-down menu and select Falling slope from the Trigger type pull-down menu.
12. Enter 75 in the Trigger value field to specify for logging to stop when the signal from the thermocouple crosses 75 with a falling slope, or falls below 75 degrees Fahrenheit.
13. Switch to the Data View tab and click the Run button to run the project continuously. The status indicator below the Project View displays Waiting for start conditions until LabVIEW SignalExpress detects that the temperature signal is above 75 degrees Fahrenheit.
14. After the start condition is met, the status indicator updates to display Recording. If the logged signal does not appear on the Data View tab, drag the signal from the Logged Data window to the Data View tab to view the progress of the log.
15. The project runs and LabVIEW SignalExpress logs the signal until the temperature falls below 75 degrees Fahrenheit and the stop condition is met. After the stop condition is met, LabVIEW SignalExpress stops recording the signal and stops running the project. Select File»Save Project to save the project.

In addition to start and stop conditions, you can use the Recording Options tab to configure LabVIEW SignalExpress to record alarms and events that occur during logging. Example 3: Displaying Alarms when a Temperature Signal Meets a Specified Value describes how to configure alarms in LabVIEW SignalExpress.