How should we choose our sensors when measuring the vibration of technical equipment?

The determination of measurement parameters largely depends on the machine equipment itself. For example, in flexible rotors such as steam turbines and rotary compressors, the majority of the force generated by the rotor is consumed in the relative motion between the shaft and bearings. Non contact sensors are used to measure the relative displacement between the shaft and bearings. On the contrary, for rigid rotors such as electric motors, most of the force generated by the rotor is consumed in the structural motion, so it is best to use speed sensors or acceleration sensors to measure the vibration of the housing.

When the rotating components are located inside the equipment that is not easily accessible, speed or acceleration sensors can generally only be used, and displacement signals can be obtained by integration when necessary.

The response of mechanical equipment status is another aspect that needs to be considered in the process of selecting sensors, that is, the maximum amount of change that the measured parameter should be able to display or respond to when the mechanical equipment status changes.

The frequency range of mechanical equipment is the third aspect to consider when selecting sensors. If the frequency range includes high-frequency components such as gear meshing, it is best to choose an accelerometer for measurement. If the measurement is limited to operating frequency, displacement or velocity sensors should be selected for measurement depending on the specific situation.

The working frequency of the vibration sensor should cover the highest frequency or the highest effective frequency being measured. In general, the upper limit frequency of non-contact displacement sensors is about 2kHz, while speed sensors are limited by their structure to a frequency range of 10-1500Hz. Acceleration sensors have the widest frequency range among all vibration sensors and can measure vibration frequencies from below 0 1Hz to over 20kHz. Therefore, vibration parameters and sensors should be selected reasonably according to specific operating conditions to meet measurement requirements.

The following situations commonly use displacement sensors.

① Flexible rotor.

② When the displacement amplitude parameter is particularly important.

③ Low frequency vibration, where the velocity and acceleration values are too small to be measured using velocity or accelerometer.

The following situations can use speed sensors.

① When the vibration frequency is low.

② When detecting mobile modes, the use of speed sensors is mostly handheld contact measurement, rather than fixed methods.

③ When evaluating the degree of mechanical failure using vibration intensity.

Acceleration sensors can be used in the following situations.

① When detecting vibration of rolling bearings or gears, or analyzing blade faults in the high-frequency domain.

② High frequency vibration, if the measured vibration frequency is higher than 1kHz, an accelerometer is required.

③ Due to limited measurement space, it is not allowed to use piezoelectric acceleration in situations where the sensor volume is large, important, or large.

④ The sensor requires a long lifespan.