Scale Signals to Engineering Units

You must scale a signal to the appropriate engineering units (EU) before you perform measurement analysis.

The NI Sound and Vibration Toolkit expect input signals and return results with the appropriate units, such as time-domain signals in the correct EU, integrated signals in units of velocity or displacement, frequency spectra in decibels with the proper reference, phase information in degrees or radians, and so on. To handle units properly, the Sound and Vibration Toolkit requires the signal to be scaled to the appropriate EU.

NI-DAQmx scales the acquired data to engineering units when a specific measurement type is selected. NI-DAQmx scales the data to Pascals when a sound pressure measurement type is selected, and scales the data to g (gravitational acceleration) or m/s² when an acceleration measurement type is selected. The Sound and Vibration Measurement Suite maintains these engineering units through subsequent measurement analysis.

You also can choose to define an NI-DAQmx task or global virtual channels in Measurement & Automation Explorer. You can use global virtual channels in applications and environments that require identical channel configuration. For example, you can define a global virtual channel to perform acceleration measurements. The global virtual channel includes channel configuration such as physical channel, measurement type, terminal configuration, input range, coupling, IEPE, sensor sensitivity, and so on.
Note National Instruments provides several tools and methods to apply scaling to a waveform. These include, but are not limited to, NI-DAQmx tasks or global channels created with Measurement & Automation Explorer or the DAQmx Create Virtual Channel VI. You also can use Scaling VIs of the Sound and Vibration Measurement Suite or your own scaling function. Scale your data from voltage to engineering units only once.