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A vibration meter measures changes in the baseline vibration patterns of machinery components. These changes can indicate mechanical malfunctions that can result in costly repairs.These devices are usually handheld and provide different types of vibration analysis, which might include recording acceleration, displacement, and velocity along with internal temperature readings. Liquid crystal displays provide the readings, which may be stored in the vibration meter for future reference or transferred to computers for condition monitoring.
Maintenance engineers can use vibration sensing tools for monitoring the compressors, fans, gearboxes, and pumps. Using vibration meters on a regularly scheduled basis, as part of monitoring machinery performance, alerts personnel when parts become loose or worn. Many vibration meters display the vibration measurement of rotating engine components. Some devices might require actual contact with the machine part, while others relay information by using laser beams and reflective tape. These tools not only measure the amount of vibration but may also provide the number of rotations per minute.
Vibration meters are often designed to provide readings in the user’s choice of units. Displacement measurements are generally displayed in inches or millimeters, velocity measurements are indicated as inches or millimeters per second, and acceleration measurements are usually indicated in either feet or meters per second squared. Certain models of vibration meter provide acceleration and velocity measurements, while others include displacement readings.
Displacement generally denotes amplitude or the distance of change from a specific reference point. Readings may further indicate average displacement or peak levels. Velocity is the rate of changing displacement, and acceleration indicates the rate of changing velocity. Vibration meters differ in their capacity to measure frequency. Displacement vibrations typically occur in the low frequency range, velocity vibrations usually occur in the low to medium frequency ranges, and acceleration vibrations generally occur anywhere between the low to high frequency levels.
Frequency levels read by a vibration meter are generally shown in hertz (Hz) and kilohertz (kHz). Some models might provide the same frequency range for displacement, velocity, and acceleration vibrations. More expensive models usually measure different frequency ranges for each type of vibration. For example, readings for displacement frequencies may range from 10 Hz to 500 Hz, velocity frequencies from 10 Hz to 1 kHz, and acceleration frequencies from 10 Hz to 10 kHz.
Movement analysis is done by comparing stored readings on a vibration meter in the form of numerical or graphical displays. Some units include computer software and others offer optional computer programs. Transferring data to the computer-based program through a transfer cable generally allows users to evaluate information in greater detail.