Basic Vibration Analysis in a Laboratory Classroom Using Virtual Instruments

Abstract

The use of virtual instruments in a laboratory classroom setting for basic vibration analyses is presented. The objective of the laboratory experience is to experimentally measure the natural frequencies and damping ratio of a cantilever beam. The acceleration amplitudes due to an impact loading are measured with an accelerometer and processed with a National Instruments myDAQ data acquisition system. The myDAQ system comes with a standard set of virtual instruments including a dynamic signal analyzer and an oscilloscope, both of which are used in this laboratory. These virtual instruments are used to interface and measure actual sensor data. The dynamic signal analyzer is used in real time to analyze the accelerometer data and identify the natural frequencies of the system. It has many settings that allow the user to change the frequency range and sampling rate along with various windowing options. In this manner, the students are exposed to how each of these parameters, as well as the impact type and location, influences the signal captured and the resulting natural frequencies observed. The oscilloscope is used to capture the accelerometer signal for a relatively short period of time to calculate the damping ratio of the beam. Several periods of oscillations are captured to then find the logarithmic decrement and the corresponding damping ratio. The use of virtual instruments has been found to be a cost-effective means to expose students to basic vibration analysis without the expense and complexities of multiple pieces of hardware for multiple lab stations. The system also provides an effective tool for many other laboratory exercises with the use of the other virtual instruments such as the digital multimeter, function generator, and power supplies.