What is vibration? Vibration measurement methods

Vibration is the oscillation or movement of an object back and forth. To start the vibration, an external or internal force is needed to make the vibration happen. It means that some energy enters through the applied force. But how can we measure vibration? What is the frame of reference for measuring vibration? Stay with us to answer the above questions. In this series of educational articles by Brenna Paish, we are going to discuss what is the topic of vibration? Let's check the vibration measurement methods completely. Stay with us.

What is vibration?

Vibration is the static and dynamic imbalance of equipment. Vibration is the oscillation or movement of an object back and forth. To start the vibration, an external or internal force is needed to make the vibration happen. It means that some energy enters through the applied force.

Once we have introduced the energy to vibrate the system, how do we define the vibration? Amplitude and frequency are common features. It also becomes important when we deal with multiple levels of vibration. The force we apply to the vibration directly affects the vibration. The more force we apply, the greater the vibration amplitude. But what limits vibration? When we increase the stiffness, like a spring, the vibration decreases. It can be said that 3 physical properties control vibration:

mass

Hardness

damping

Vibration measurement

The main characteristics of the vibration signal that we measure:

Domain

Frequency

Phase

oscillating field

1. Domain

The measurement range is the intensity of the vibration. And it can be expressed in 3 different ways, depending on the signal we are measuring: Peak to Peak, Zero to Peak and RMS.

Vibration is measured in terms of displacement, velocity or acceleration. Vibration displacement is always measured peak-to-peak. For example, measuring the total rotation of the rotor or the body of the device in MILS or MICROMETERS is done in this way. Vibration velocity and acceleration are measured as zero-to-peak or RMS. The units used for velocity are "inches per second" or "millimeters per second" and for acceleration in "G" or "meters per second".

Dear Yeonsig Nam, TDM is calculted by default in Gaussian within a TD or CIS job, see e.g. https://gaussian.com/td/

Best, Pablo

Hi Pablo, thanks for your answer but I'm looking for a transition between vibrational states coupled to different electronic states, not between electronic states