Generating a Non-repetitive Noise Signal or Phase Continuous Signal

NI-DAQmx-supported devices can update their output buffer while running and generate phase continuous or non-repetitive noise signals.

Complete the following steps to generate a non-repetitive noise signal.

1. Place the Create Analog Signal step in the Project View.
2. In the Signal type pull-down menu, select Noise Signal.
3. Enter 10k in the Sample rate field.
4. Make sure there is no checkmark in the Repeated signal checkbox.
5. Click the Add Step button and select Generate Signals»DAQmx Generate»Analog Output and select Voltage or Current.
6. On the Configuration page of the Step Setup tab for the DAQmx Generate step, select Continuous Samples from the Generation Mode pull-down menu.
7. Run LabVIEW SignalExpress continuously. The Create Analog Signal step produces a new noise pattern at each iteration and passes the pattern to the DAQmx Generate step that loads it into the analog output device, resulting in a non-repetitive noise generation.

You can use the Create Analog Signal and the DAQmx Generate steps to generate a phase continuous signal of any arbitrary frequency. Complete the following steps to generate a phase continuous noise signal.

1. Place the Create Analog Signal step in the Project View.
2. In the Signal type pull-down menu, select a Sine Wave and specify an arbitrary Frequency.
3. Remove the checkmark from the Repeated signal checkbox so that each iteration of the signal is contiguous to the previous iteration.
4. Run LabVIEW SignalExpress continuously. The Create Analog Signal step produces a continuous signal with increasing timestamp and phase continuity.

To maintain phase continuity of a generated signal, LabVIEW SignalExpress must sustain a minimum loop rate. The minimum loop rate is equal to the sample rate divided by the number of samples in the signal. If LabVIEW SignalExpress cannot sustain the minimum loop rate, remove any unnecessary graph display plots in the Data View and close any configuration views. If the software still cannot sustain the minimum loop rate, decrease the sample rate or increase the buffer size to decrease the loop rate.

Refer to the Continuous Noise Generation and Finite Acquisition (Non Regeneration) example located in the SignalExpress\examples\DAQmx directory for an example of generating a true noise signal.