Not all M and X Series devices support analog triggering on all channels. To determine what physical channels can be used as analog triggers, see the specifications document for your specific M Series or X Series device. You can find the specifications document for your device by searching for your device model number at NI Product Manuals.
To use analog triggering, change the polymorphic selector on the DAQmx Start Trigger vi to 'Start Analog Edge', as shown in the snippet below:
Notice that by default the source terminal of the VI is a string data type instead of a DAQmx physical channel data type. Consequently, you will have two options:
- Create a DAQmx physical channel constant or control and wire it into the source terminal to be coerced to a string, and select the physical channel to trigger off of from the dropdown menu.
- Type out the correct name for the specific physical channel that you would like to use into a string constant or control.
Additional Information
Note:
When configuring an analog input channel as a trigger source, the selected channel must also be included in the acquisition task. The reason is that the analog triggering mechanism relies on the same hardware configuration used for data acquisition. Therefore, the device must actively acquire from the specified channel in order to evaluate the trigger condition. If the trigger source channel is not part of the task, NI-DAQmx will return the following error:
Note: For tasks that include multiple analog input channels, the trigger source channel must be listed first in the physical channel list. The reason is that, due to the device’s internal multiplexing and trigger routing architecture, the analog trigger source must correspond to the first channel in the scan list. This ensures proper alignment between the trigger evaluation circuitry and the acquisition sequence. If the trigger channel is not the first channel in the list, NI-DAQmx will return the following error: