Sound, which can either be low, soft or loud, is created by vibrations. When an object moves rapidly back and forth, the air molecules around it are disturbed. The disturbance moves away from the object in waves, which is what is interpreted as sound. Vibrations can be measured with different instruments. Measuring the amount of vibration is critical in some industries and production processes. There are sensitive machineries that can be affected by too much vibration. Exposure to vibration of workers in different industries is also monitored as this relates to their health and safety while working. Just think of a person using a jackhammer. Imagine how a person's whole body is affected by the vibration produced by the jackhammer. Below are some ways to measure vibrations.
- One of the common devices used to measure vibration is a piezoelectric accelerometer. This instrument is used in industries where the exposure to workers to vibration is measured. The device is attached to a vibrating machine that is to be analyzed. The whole device comes with a frequency analyzer, a recorder, an amplifier and an oscilloscope. The force that is produced by the vibration produces a corresponding electrical signal that is in direct proportion to the amount of vibration acceleration applied to the instrument. The instrument reading is expressed in meters per second square.
- For rotating machines, a velocity transducer or a velocity pickup is used. The instrument has a coil of wire within. Vibration is translated into electrical energy, which is then measured. The velocity signal that is produced in once cycle when measured is equivalent to twice the maximum value. The second value should be the same as the first value even they are in different directions. Since velocity is measured in one direction only, the reading should show a wave from the lowest point or zero to the highest point or the peak of the velocity. When using a velocity pickup to measure vibrations in rotating machines it is important that you use a unit whose response will be within the machine's expected vibration frequencies.
- Modern laboratories use more sophisticated and smaller, hand-held versions of the accelerometer and velocity transducer in different applications. These are electronic versions with graphical and digital displays. These tools are used to measure sensitive and precision laboratory instruments to calibrate them.
- The earth's vibrations particularly during an earthquake are measured with a seismograph. The earth gives off two kinds of waves, the surface wave and the body wave. The surface waves as the name implies travel on the surface of the earth while the body waves travel through the earth's layers. The seismograph has three pendulums attached to a base that supports them. One pendulum records the vertical movements and the other two record the horizontal movements. The pendulums are connected to a recorder, such as a pen that records the intensity of the earth's movement on paper during an earthquake.
Vibration can both be useful and harmful. It is useful in some industries like transporting mineral and rocks on a conveyor belt used by drilling companies, ultrasonic cleaning baths, pile drivers and concrete compactors. It is harmful when continued exposure to vibration can cause machine breakdowns as well as when excessive vibration affects the health of workers. Correct measurements in both cases are necessary to make vibration useful in selected industries and eliminated in others.