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The Input signal plot of the Getting Started Exercise VI is a vibration signal plot. Vibration signal plots illustrate how sound or vibration signals change over time. You can use a speed profile plot to illustrate how rotational speed changes over time. You then can use these two plots in parallel to observe how raw sound or vibration changes with speed.

The Analog Tacho Processing Express VI uses an analog tachometer signal to determine the rotational speed of a device under test. You can use this Express VI to compute the rotational speed of the computer fan.

Press the <Ctrl-E> keys to switch to the block diagram of the Getting Started Exercise VI. Notice that the oax_Load Data (Analog Tacho, single channel) VI loads the example data and returns both the vibration signal as an analog tachometer signal as well as information about the tachometer. You also can see several indicators on the block diagram of the Getting Started Exercise VI. You will use these indicators in later exercises.

Complete the following steps to compute the rotational speed of the computer fan and to display the information in a speed profile plot.

1. Place the Analog Tacho Processing Express VI on the block diagram of the Getting Started Exercise VI. A configuration dialog box appears.
   
    
   
   
2. On the Configuration page, set Pulse/Revolution to 2. Recall that you acquire the pulse per revolution information in the Tacho info indicator when you run the Getting Started Exercise VI for the first time.
3. Click the OK button to save the current configuration and close the configuration dialog box.
4. Wire the analog tacho signal output of the oax_Load Data (Analog Tacho, single channel) VI to the analog tacho signal input of the Analog Tacho Processing Express VI.
5. Wire the speed profile output of the Analog Tacho Processing Express VI to the Speed profile indicator.
   
   The block diagram should appear similar to the following block diagram.

6. Run the Getting Started Exercise VI to calculate the rotational speed of the computer fan and to display the information in the Speed profile plot.
7. Save this VI.

On the front panel, the Waveform and Speed page displays vibration signal and speed profile plots of the example data. From the Input signal plot, you can see that the vibration amplitude of the computer fan generally increases over 15 seconds. The Speed profile plot shows that the rotational speed of the computer fan increases steadily from approximately 1,400 RPM to 3,700 RPM over 15 seconds. The Input signal and Speed profile plots therefore illustrate that the vibration amplitude is approximately linearly related to the rotational speed of the computer fan.

Previous: 1. Loading the Example Data

Next: 3. Analyzing the Colormap

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