Design of Amplifying Circuit in Bearing Vibration Sensor
When the bearing vibration is detected, the vibration signal collected by the sensor is relatively weak and mixed with noise, so a charge amplifier with simple structure and convenient debugging is designed to improve the signal, reduce noise interference, and improve the signal-to-noise ratio to meet the requirements of subsequent signal processing.
The relevant national standards for bearing measurement have a division of the frequency of the vibration signal, including the general frequency of 50-10KHz, the low frequency of 50-300Hz, the intermediate frequency of 300-1800Hz, and the high frequency of 1800-10KHz. More accurate vibration can be extracted after segmentation Information. The frequency response of the amplifying circuit to different frequency signals is not less than 0.707 times of the theoretical magnification without distortion, and at the same time it has the advantages of high input impedance, low output impedance, low noise interference and wide output frequency bandwidth.
The design of the charge amplifier mainly includes two parts: (1) amplifier circuit (2) filter circuit
amplifying circuit
Practical data shows that it is ideal to set the multiple of the amplifier to 1000, considering the amplification of the unipolar amplifier
The magnification is relatively limited, so it is most reasonable to use 2-stage amplification.
filter circuit
It is required to ensure that the frequency characteristic curve of the signal is flat and free of fluctuations in a large frequency range.
Source 2nd order Butterworth low pass filter.
Validation results
The signal generator is used to input sine waves with different frequencies and the same amplitude, and the output of the charge amplifier is recorded through the oscilloscope.
Through the analysis of the experimental data, the designed charge amplifier has a magnification of about 1000 times, a good filtering effect, a frequency response that meets the relevant requirements of the national standard, and is easy to debug, so it can be well applied in the bearing vibration measuring instrument.
The charge amplifier (dual channel) is shown in the figure below:
