Vibration sensor principle and application - Solutions - Huaqiang Electronic Network

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In the highly developed modern industry, the development of modern testing technology to digitalization and informationization has become an inevitable development trend. The front end of the test system is the sensor. It is the soul of the whole test system and is listed as a cutting-edge technology by the countries in the world. It is a rapidly developing IC technology and computer technology in recent years, which provides a good and reliable scientific and technological foundation for the development of sensors. The development of sensors is becoming more and more prosperous, and digitalization, versatility and intelligence are important features of modern sensor development.
I. Engineering Vibration Test Method In the field of engineering vibration test, the test methods and methods are various, but according to the measurement methods of various parameters and the physical properties of the measurement process, they can be divided into three categories.
1. The mechanical measurement method converts the parameters of the engineering vibration into mechanical signals, and then performs measurement and recording after being amplified by the mechanical system. The commonly used instruments are a lever type vibrometer and a Geiger vibrometer, which can measure the frequency. Lower and less accurate. However, it is simple and convenient to test in the field.
2. The optical measurement method converts the parameters of the engineering vibration into optical signals, which are displayed and recorded after being enlarged by the optical system. Such as reading microscopes and laser vibrometers.
3. The electrical measurement method converts the parameters of the engineering vibration into electrical signals, which are displayed and recorded after being amplified by the electronic circuit. The main point of the electrical measurement method is to convert the amount of mechanical vibration into electric quantity (electromotive force, electric charge, and other electric quantity), and then measure the electric quantity to obtain the mechanical quantity to be measured. This is currently the most widely used measurement method.
Although the physical properties of the above three measurement methods are different, the measurement systems are basically the same, and they all include three steps of picking up, measuring and amplifying lines and displaying records.
1. Pick up the link. The measured mechanical vibration is converted into a mechanical, optical or electrical signal, and the device that performs this conversion is called a sensor.
2. Measuring lines. There are many types of measurement lines, and they are all designed for the transformation principle of various sensors. For example, the measuring circuit for the piezoelectric sensor has a voltage amplifier, a charge amplifier, etc.; in addition, there are integral lines, differential lines, filter lines, normalization devices, and the like.
3. Signal analysis and display and recording. The voltage signal output from the measuring line can be input to the signal analyzer or to the display instrument (such as electronic voltmeter, oscilloscope, phase meter, etc.) and recording equipment (such as light oscilloscope, tape recorder, X-Y) according to the measurement requirements. Recorder, etc.). It can also be recorded on a tape if necessary, and then input to a signal analyzer for various analysis processes to obtain the final result.
Second, the mechanical receiving principle of the sensor Vibration sensor is one of the key components in the testing technology, its role is mainly to receive the mechanical quantity and convert it into a proportional power. Because it is also an electromechanical conversion device. So we sometimes call it a transducer, a vibrator, and so on.
The vibration sensor does not directly convert the original mechanical quantity to be measured into electric quantity, but takes the original mechanical quantity to be measured as the input quantity of the vibration sensor, and then receives it by the mechanical receiving part to form another mechanical quantity suitable for transformation. Finally, the electromechanical conversion part will be converted into electric quantity. Therefore, the performance of a sensor is determined by the performance of the mechanical receiving portion and the electromechanical transducer.
1. Relative mechanical receiving principle Since mechanical motion is the simplest form of material motion, the first thing people think of is to measure vibration by mechanical means, thus manufacturing a mechanical vibrometer (such as Geiger vibrometer). ). The mechanical receiving principle of the sensor is based on this. The working receiving principle of the relative vibrometer is to fix the instrument on the stationary bracket during the measurement, so that the contact rod and the object to be tested have the same vibration direction, and the elastic force of the spring is in contact with the surface of the object to be measured. When the object vibrates, the lever moves with it, and pushes the recording pen to draw a curve of the displacement of the vibrating object over time on the moving paper strip. According to this recording curve, the magnitude and frequency of the displacement can be calculated.
It can be seen that the measured result of the relative mechanical receiving portion is the relative vibration of the measured object relative to the reference body, and the absolute vibration of the measured object can be measured only when the reference body is absolutely stationary. In this way, a problem arises. When it is necessary to measure absolute vibration, but can not find a stationary reference point, such instruments are useless. For example: testing the vibration of a diesel locomotive on a moving diesel locomotive, measuring the vibration of the ground and buildings during an earthquake... There is no fixed reference point. The circuit has a voltage amplifier, a charge amplifier, etc.; in addition, there are integral lines, differential lines, filter lines, normalization devices, and the like.
3. Signal analysis and display and recording. The voltage signal output from the measuring line can be input to the signal analyzer or to the display instrument (such as electronic voltmeter, oscilloscope, phase meter, etc.) and recording equipment (such as light oscilloscope, tape recorder, X-Y) according to the measurement requirements. Recorder, etc.). It can also be recorded on a tape if necessary, and then input to a signal analyzer for various analysis processes to obtain the final result.
Second, the mechanical receiving principle of the sensor Vibration sensor is one of the key components in the testing technology, its role is mainly to receive the mechanical quantity and convert it into a proportional power. Because it is also an electromechanical conversion device. So we sometimes call it a transducer, a vibrator, and so on.
The vibration sensor does not directly convert the original mechanical quantity to be measured into electric quantity, but takes the original mechanical quantity to be measured as the input quantity of the vibration sensor, and then receives it by the mechanical receiving part to form another mechanical quantity suitable for transformation. Finally, the electromechanical conversion part will be converted into electric quantity. Therefore, the performance of a sensor is determined by the performance of the mechanical receiving portion and the electromechanical transducer.
1. Relative mechanical receiving principle Since mechanical motion is the simplest form of material motion, the first thing people think of is to measure vibration by mechanical means, thus manufacturing a mechanical vibrometer (such as Geiger vibrometer). ). The mechanical receiving principle of the sensor is based on this. The working receiving principle of the relative vibrometer is to fix the instrument on the stationary bracket during the measurement, so that the contact rod and the object to be tested have the same vibration direction, and the elastic force of the spring is in contact with the surface of the object to be measured. When the object vibrates, the lever moves with it, and pushes the recording pen to draw a curve of the displacement of the vibrating object over time on the moving paper strip. According to this recording curve, the magnitude and frequency of the displacement can be calculated.
It can be seen that the measured result of the relative mechanical receiving portion is the relative vibration of the measured object relative to the reference body, and the absolute vibration of the measured object can be measured only when the reference body is absolutely stationary. In this way, a problem arises. When it is necessary to measure absolute vibration, but can not find a stationary reference point, such instruments are useless. For example: testing the vibration of a diesel locomotive on a moving diesel locomotive, measuring the vibration of the ground and buildings during an earthquake... There is no fixed reference point. In this case, we must measure with a vibrometer of another measurement method, that is, use an inertial vibrometer.
2. Inertia-type mechanical receiving principle When the inertial mechanical vibrometer is used for vibration measurement, the vibrometer is directly fixed on the measuring point of the measured vibrating object. When the sensor shell moves with the measured vibrating object, the inertia of the elastic support The mass will move relative to the outer casing, and the stylus mounted on the mass can record the relative vibration displacement amplitude of the mass element and the outer casing, and then use the relationship between the inertial mass and the relative vibration displacement of the outer casing. Find the absolute vibration displacement waveform of the measured object.
Third, the electromechanical transformation principle of vibration sensor In general, the vibration sensor in the mechanical receiving principle, only the relative, inertial two, but in the electromechanical transformation, due to different transformation methods and properties, its variety, the scope of application is also extremely widely.
The sensors used in modern vibration measurement are not traditionally independent mechanical measurement devices. They are only one part of the entire measurement system and are closely related to subsequent electronic circuits.
Due to the different internal electromechanical conversion principle of the sensor, the output power is also different. Some convert the change in the mechanical quantity into the electromotive force and the change in the electric charge, and some convert the change in the mechanical vibration amount into a change in electrical parameters such as resistance and inductance. In general, these amounts of electricity are not directly accepted by subsequent display, recording, and analytical instruments. Therefore, sensors for different electromechanical conversion principles must be accompanied by a dedicated measuring circuit. The function of the measuring circuit is to finally change the output power of the sensor into a general voltage signal that can be accepted by the analysis instrument and analyzed by the instrument. Therefore, the vibration sensor can have the following classification methods according to its function:
According to the principle of mechanical reception: relative, inertial;
According to the principle of electromechanical transformation: electric, piezoelectric, eddy current, inductive, capacitive, resistive, photoelectric;
According to the measured mechanical quantity: displacement sensor, speed sensor, acceleration sensor, force sensor, strain sensor, torsional vibration sensor, torque sensor.