You can use the FD-11601 in finite acquisition and continuous acquisition analog input applications.

The FD-11601 features the following timing and triggering signals.

AI Sample Clock Signal

A sample consists of one reading from each channel in the AI task. Sample Clock signals the start of a sample of all analog input channels in the task.

Refer to the following figure for sample clock source options.

Figure 32. AI Sample Clock Timing Options


The FD-11601 is considered a Delta-Sigma device. It contains multiple A/D converters that require a high-frequency oversample clock to produce accurate, synchronized data. The FieldDAQ device returns a sample on every Sample Clock pulse.

The oversample clock is used as the AI Sample Clock Timebase. The FieldDAQ device supplies 13.1072 MHz, 12.8 MHz, 12.288 MHz, and 10.24 MHz timebases. By default, NI-DAQmx automatically chooses the most suitable timebase for a selected data rate.[1]1 Automatic timebase coercion is supported in NI-DAQmx 18.5 and later. Previous versions of NI-DAQmx use the 12.8 MHz timebase by default.

The FieldDAQ device automatically issues a synchronization pulse to each bank that resets their ADCs at the same time. You can also specify a specific time for the synchronization pulse to occur. Because of the filtering used in the Delta-Sigma FieldDAQ device A/D converters, these devices exhibit a fixed input delay relative to non-Delta-Sigma devices in the system. This input delay is specified in the FD-11601 Specifications .

When using multiple FieldDAQ devices in a task that contains channels for a Delta-Sigma device, such as the FD-11601, ensure that one of those channels is the first in your channel list.

AI Sample Clock Timebase Signal

The AI Sample Clock Timebase signal is divided down to provide a source for Sample Clock.

AI Start Trigger Signal

Use the Start Trigger signal to begin a measurement acquisition. A measurement acquisition consists of one or more samples. If you do not use triggers, begin a measurement with a software command. Once the acquisition begins, configure the acquisition to stop in one of the following ways:

  • In finite mode, when a certain number of points has been sampled
  • In continuous mode, with a software command

You can specify a default delay from the Start Trigger to the first sample.

Use the Start Trigger signal with a time source, by specifying a specific time in NI-DAQmx. Refer to Time Triggering in the NI-DAQmx User Manual for more information on accessing time-based features in the NI-DAQmx API.

Analog Input Sync Pulse

You can use time as a trigger for sync pulses on the FieldDAQ device.

To use a sync pulse with a time source, specify a specific time in NI-DAQmx. Refer to Time Triggering in the NI-DAQmx User Manual for more information on accessing time-based features in the NI-DAQmx API.

Note To accurately synchronize Delta-Sigma devices in two or more separate tasks, you must specify the same sync pulse. Otherwise, a sync pulse is initiated by software implicitly, even if time start triggers are specified for the tasks. However, for multidevice tasks, the sync pulses and start triggers are automatically synchronized.

1 Automatic timebase coercion is supported in NI-DAQmx 18.5 and later. Previous versions of NI-DAQmx use the 12.8 MHz timebase by default.