Before connecting any signals, locate your device pinout.
An IEPE sensor needs an appropriate cable and/or connector to hook into the BNC inputs of the C Series module.The next step is to physically connect the microphone to your DSA device. NI DSA devices use BNC or SMB connectors. The center pin of the connector, AI+, provides the DC excitation, when enabled, and the positive input signal connection. The shell of the connector, AI-, provides the excitation return path and the signal ground reference. To minimize ground noise, keep the metal shells of the connectors from touching each other, the DSA device(s), or the chassis/computer.
You can use MAX to quickly verify the accuracy of your measurement system setup. Using an NI-DAQmx Global Virtual Channel, you can configure a microphone measurement without any programming. A virtual channel is a concept of the NI-DAQmx driver architecture used to represent a collection of device property settings that can include a name, a physical channel, input terminal connections, the type of measurement or generation, and scaling information.Follow these steps to begin:
With MAX still open, click back on the NI-DAQmx Global Virtual Channel tab and click on the Run button. You see the sound pressure value of your measurement displayed at the top of the screen.
Figure 5. Testing the virtual channel in MAX.
You can choose to view the signal in tabular form or as a graph by selecting Graph from the Display Type pull-down menu. You also have the option of saving your NI-DAQmx Global Virtual Channel should you wish to refer to this configuration screen again in the future.
Once you have configured the system properly, you can acquire and visualize data using the LabVIEW graphical programming environment.You can find examples for your device from any LabVIEW window by selecting the following: Help » Find Examples. Once in NI Example Finder, browse to the Sound and Vibration examples by selecting Toolkits and Modules » Sound and Vibration » Analyzing and Processing » Sound Level Measurements » Sound Level Meter (DAQmx).vi.With the Sound Level Meter (DAQmx).vi shown, you can continually acquire sound pressure data from the specified channel. This VI then applies the specified weighting filter, computes a third-octave spectrum, and measures the equivalent continuous level (Leq) and a decimated exponential average level.
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