One of the important cases in different control industries Vibration Rotating tools and machines such as generator turbines, pumps, bearings, motors, fans, etc., and if they exceed a certain limit, can lead to accidents or equipment failure, therefore Vibration measurement Parts and machines are of great importance in various industries, measuring this Fluctuations and vibrations By Vibration meter or Vibration meter will be done.
Vibration meter Frequent application in maintenance Industrial equipment Movable, in more advanced models of vibrometers it is possible to measure speed, acceleration, displacement range.
The vibration of a mechanical oscillation is around an equilibrium point. This oscillation can occur periodically like a clock pendulum or randomly at different intervals of time. A vibrometer is actually an instrument that measures these fluctuations and vibrations for us. Parameters such as frequency or time frequency, Speed, Acceleration, spatial displacement and in more advanced models can make advanced oscillating movements analyze Slowly Use a vibrometer or Vibrometer It will be widely used in the maintenance of many mobile industrial equipment.
When these oscillations exceed the defined range, they will cause irreparable damage to industrial equipment, and continuous inspection of vibration of motors and rotating equipment will prevent damage caused by them.
- Vibration sensors Vibration
sensor The first element required for Vibration measurement And it is a device that senses vibrational motion and converts it into an electrical signal proportional to vibrational motion. By converting vibrations into electrical signals, it is possible to store, perform further processing and also view the signal through electronic devices (data collection equipment).
Vibration sensors are usually divided into two groups: - Relative motion (vibration) sensors: Vibration It is measured by these sensors relative to a fixed reference point, such as eddy current sensors.
- Absolute motion (vibration) sensors: such as sensors Speedometer And accelerometer
According to the working mechanism and the main measurement parameter, the vibration sensors that are used in rotary machines today are:
1- Transfer meter
2- Speedometer 
3- Accelerometer
Displacement sensor (transducer)
These sensors are non-contact. These types of sensors are also called eddy current sensors.
The basis of this type of sensor is based on the production of a magnetic field in a coil that is embedded in the tip of the sensor. This magnetic field induces a vortex current in the axis of rotation (shaft), which is an electrical conductor. The closer the electrical conductor is to the page wire, the higher the energy absorption in the conductor. A system that uses eddy current sensors consists of an oscillator, a communication cable, and a probe.
The oscillator generates a high frequency signal (radio frequency) to send to the sensor (probe) and this signal creates a magnetic field around the sensor. Since the magnetic field is affected only by the conductor objects, there will be no effect on the magnetic field and consequently no reduction in the RF signal until the conductor body is in front of the sensor. As a conductor approaches the magnetic field, this field penetrates the conductor and creates eddy currents on its surface, resulting in reduced return energy and RF signal amplitude, oscillator and detector of RF signal amplitude. Measures and generates a direct voltage in proportion to its peak points.
How a displacement sensor of a vibration type works
As shown in the figure above, depending on the rotation of the conductor body, the amplitude of the RF signal also changes due to the displacement of the conductor surface, and it is as if a signal with amplitude modulation is generated that oscillates around a DC signal. .
The DC signal indicates the position of the object and the AC signal indicates the amount of vibration.
The non-contact vibration sensor has a linear range of operation and when setting it up and connecting it to the display system, it should be noted that the sensor is located at a distance from the conductor / shaft body where the operating point is in an area. Do not deviate from the linear range of the sensor in case of maximum oscillation.
During installation, care must be taken that the tip of the sensor is not damaged and is tightly closed in the desired location. In addition to the sensor length set, the communication cable to the oscillator / detector is specified and calibrated by the manufacturer, and if for any reason this length changes, the system must be restarted.Calibrated Appeared.
Vibration measurement sensors of the accelerometer
type. This type of sensor or transducer is installed on the body of the object and hence it is called contact or body sensor. The basis of the operation of this sensor is that after installation on the object, according to the amount of vibration of the object, the outer shell of the sensor vibrates and this movement moves the magnet that is installed inside the transducer and is connected to a spring in Bringing and moving the magnet creates a voltage in the coil. Due to the fact that the voltage changes are proportional to the speed of movement of the magnet, the absolute speed of vibrational motion of the object can be measured from the voltage.
As mentioned above, to measure vibration, the sensor must vibrate, so it is necessary to consider the natural frequency of the sensor, in other words, the sensitivity of the sensor to all frequencies should be the same and equal to the value set for the sensor. Be. Therefore, the frequency range that can be used for the sensor is the range outside the normal frequency range of the sensor and is located in an area whose frequency response is so-called flat.
These sensors do not require a power supply but are sensitive to external magnetic fields.
Accelerometer-type vibration measuring
sensors These sensors are also contact-type and use a piezoelectric element to convert the acceleration into an electrical signal. The piezoelectric element generates electric charges at two levels in proportion to the force exerted on it.
In the original design of the accelerometers, this electric charge, equal to Pico Columbus, was used as the sensor output. In today’s designs using in-sensor amplifiers, this electric charge is amplified and used in mv as the sensor output.
Accelerator transducers typically have two structures, compression type and shear type. In the compression type, the piezoelectric is separate from the base and is therefore less sensitive to heat.
Another difference between the two types of acceleration sensors is in the use of signal modifiers, so that some acceleration sensors are equipped with an electronic circuit to amplify the signal, and because this part is built into the sensor, the operating temperature of these sensors is limited.
Accelerometers measure absolute vibration. Some manufacturers also use an integral circuit inside the acceleration sensor to show the amount of vibration of the speed type.
How to install vibration
sensors Vibration sensors are installed on cars in various ways, including:
Permanent installation: where the sensor is connected to the machine using screws or welds.
Magnetic installation: which is often in Measuring Equipment It has a portable user.
Manual method: In this method, the sensor is held in the desired location when used by hand.
Rose Calibration Company in Melbourne, Australia with over ten years of experience provides all calibration, maintenance, and repair services throughout Australia. If you live in Sydney, Melbourne, Adelaide, Perth, Geelong, and Brisbane, you can receive your quote in less than two hours by fill-up the form via the “Booking” link.
