When you take measurements with a data-acquisition system, you often must program the system to get the right amount of data at the right time. The way you initiate, or trigger, the acquisition makes a significant difference in the quality of the data you collect. By learning about your options, you'll know which combination of hardware and software triggers to use and whether the triggers should be analog or digital.
Different events require different triggers.
Software triggers are easy to develop. You program the system to start an acquisition when a software event occurs, such as when a program starts or when you click on a button on a user screen. Listing 1 contains some code for a software trigger. Applications that employ triggers beyond basic software triggering usually do so to reference the acquisition to an external event or time. For example, when you measure vibration in a crash test, you may need to capture data for the 10 ms that immediately follow the impact.