Principle of vibration analyzer
principle
Vibration analyzer vibrometers are generally piezoelectric, and there are roughly two types of structures: 1 compression type; 2 shear type, vibration analyzer principle is to use the piezoelectric effect of quartz crystal and artificially polarized ceramic (PZT). Designed. When a quartz crystal or an artificially polarized ceramic is subjected to mechanical stress, a charge is generated on the surface thereof, and the magnitude of the charge density formed is strictly linear with the magnitude of the applied mechanical stress. At the same time, the mechanical stress is proportional to the acceleration value under certain sensitive mass. Under certain conditions, the charge generated by the piezoelectric crystal is proportional to the perceived acceleration.
The generated charge is output by the charge amplifier and other arithmetic processing. It is the data we need. Q=dij?F=dij?ma where: Q-piezoelectric crystal output charge, dij-piezoelectric crystal second-order piezoelectric Tensor, sensitive mass of m-acceleration, a-accepted vibration acceleration value. The vibrometer piezoelectric accelerometer bears the amount of charge output per unit of vibration acceleration value, and its charge sensitivity is expressed in units of pC/ms-2 or pC/g (1g=9.8ms-2). The vibration accelerometer is essentially equivalent to a charge source and a capacitor. After the equivalent circuit is simplified, the voltage sensitivity of the accelerometer can be converted to Sv=SQ/CaSv-, the voltage sensitivity of the accelerometer, mV. Charge sensitivity of /ms-2SQ-accelerometer, capacitance sensor of pC/ms-2Ca-accelerometer Piezoelectric speed sensor, which adds an integral circuit to the piezoelectric accelerometer by passing an acceleration signal By dividing the product once, you can get the speed value of the vibration!
Measurement method
1. Using the vibration analyzer to check the status of the equipment, although it can not be used as the sole basis for the equipment overhaul cycle, it is very necessary as a reference condition. Since the speed of pumps, fans and other equipment is low, the damage caused by vibration is not unique. For example, sometimes there is no problem with the vibrometer, but the impeller is severely corroded and needs to be overhauled. Therefore, it is determined that the equipment overhaul period should be comprehensively considered from the aspects of the vibration meter test results, the cumulative operation time of the equipment, and the efficiency.
2. The application of vibration analyzer detection is also necessary as an acceptance method after equipment overhaul. It should be pointed out that due to the different degrees of old and new equipment, the inspection value of the acceptance is not uniformly defined. It should be based on the detection value of the pump group before the overhaul, and the inspection value of the repair value is not made. Uniform provisions shall be based on the test value before the overhaul of the pump set being accepted, and the repair value shall be lower than the pre-repair value. In addition, the application of the vibrometer can also find pump group installation problems (including poor alignment, long-term loosening of anchor bolts), and cavitation of the pump.
In short, the vibration analyzer and other testing instruments are used together to facilitate analysis of the operating state of the equipment. If the vibrometer is combined with oil quality analyzer, motor fault detector and other instruments, it can more accurately judge the operation of the equipment.
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