Can eddy current sensors be used in a vacuum?

OK. Proximity sensors measure the distance between the measured metal conductor and the probe surface in a static and dynamic non-contact, high-linearity, high-resolution manner. It is a non-contact, linearized metrology tool.

The eddy-current sensor accurately measures the static and dynamic relative displacement changes between the body to be measured (which must be a metal conductor) and the probe end face.

In the state analysis, vibration research, analysis and measurement of high-speed rotating machinery and reciprocating moving machinery, a variety of parameters of the rotor vibration state can be continuously and accurately collected for non-contact high-precision vibration and displacement signals. Such as the radial vibration of the shaft, the amplitude, and the axial position. From the theoretical analysis of rotor dynamics and bearing science, the motion state of large rotating machinery mainly depends on its core - the rotating shaft, and the eddy current sensor can directly measure the state of the rotating shaft without contact, and can provide key information for the early judgment of mechanical problems such as rotor imbalance, misalignment, bearing wear, shaft cracks and friction.

The eddy current sensor has been widely used in the monitoring and fault diagnosis of large rotating machinery due to its advantages of good long-term work reliability, wide measurement range, high sensitivity, high resolution, fast response speed, strong anti-interference force, not affected by oil pollution and other media, and simple structure.

Resources.

1. The eddy-current displacement sensor can measure the relative position of the measured body (must be a metal conductor) and the end face of the probe.

2. The eddy current displacement sensor has good long-term working reliability, high sensitivity, strong anti-interference ability, non-contact measurement, fast response speed, and is not affected by oil and water and other media, and is often used for long-term real-time monitoring of shaft displacement, shaft vibration, shaft speed and other parameters of large rotating machinery, which can analyze the working conditions and failure causes of the equipment, effectively protect the equipment and carry out first-class maintenance.

3. From the theoretical analysis of rotor dynamics and bearing science, the operating state of large rotating machinery mainly depends on its core-rotating shaft, while the eddy-current displacement sensor can directly measure the state of the rotating shaft, and the measurement results are reliable and credible.

The eddy current sensor accurately measures the relative position of the measured object and the end face of the probe through the principle of eddy current effect, which is characterized by good long-term work reliability, high sensitivity, strong anti-interference ability, non-contact measurement of the amount of rent, fast response, and is not affected by oil and water and other media, and is often used for long-term real-time loose wheel monitoring of the shaft displacement, shaft vibration, shaft speed and other parameters of large rotating machinery, which can analyze the working conditions and failure causes of the equipment, and effectively protect and pre-repair the equipment.

The principle of an eddy current sensor is to generate an electromagnetic field, when approaching a conductor, the conductor will produce a reverse electromagnetic field, and the sensor senses the electromagnetic field generated by the conductor to know the position of the measured object. The principle of eddy currents such as KD2306 KD2446.

Therefore, the eddy current sensor requires that the measured body must be a conductor, and because the measured body needs to generate a reverse electromagnetic field, the measured body needs to have a certain area, which is generally 3 times the area of the probe of the eddy current sensor. In order to generate current on the measured body, a certain thickness is also required, and generally more than the thickness is acceptable.

Summarize the requirements of the test body:

1. The object to be measured is a conductor; 2. The surface of the measured body is flat and has a certain area; 3. The measured body has a certain thickness;

In addition, it depends on the specific model of the eddy current sensor, such as KD2306 can measure aluminum and iron, KD5100 can only measure aluminum. 1. The eddy-current sensor can realize non-contact measurement of a variety of physical quantities on the surface of the object as a metal conductor. It can be used to measure vibration, displacement, thickness, speed of revolution, temperature, hardness and other parameters, and can also perform non-destructive testing. ,1,

This is due to the principle of eddy current transducer sensor, there are many eddy current sensing devices on the market, imported more zhi

The good one is the KD2306 made in the United States.

Because the electric DAO eddy current sensor generates an electromagnetic field, the measured body needs to be able to conduct electricity to generate a reverse electromagnetic field, and the distance of the measured body is judged according to the strength of the reverse electromagnetic field.

The conductivity of the test body determines the strength of this reverse electromagnetic field, so each eddy current sensor needs to be calibrated for the test body. For example, if a sensor is calibrated with aluminum, if it is used to measure copper, the measurement value will definitely not be accurate.

To sum up, the requirements for the subject are very strict.

The eddy current sensor relies on the eddy current generated inside the material to complete the measurement. Materials that can generate large DAO eddy currents are conductive materials with good energy rights, such as copper, aluminum, silver, etc. The insulating material does not generate eddy currents, which makes it impossible for eddy current sensors to detect the insulating material.

Magnetic materials (e.g. iron, nickel, etc.) produce very little eddy currents, which greatly reduces the sensitivity of eddy current sensors. Therefore, eddy current sensors do have strict requirements for the material to be measured.

Requirements for the subject to be measured.

In order to prevent the magnetic field generated by eddy current from affecting the normal output of the instrument, a certain range of non-conductive dielectric space must be left around the sensor head during installation, if more than two sensors are installed at the same time in a certain part, it is necessary to consider whether there will be cross-interference, the specified distance must be maintained between the two probes, the surface area of the measured body should be more than 3 times the diameter of the probe, and when the requirements of 3 times cannot be met, it can be appropriately reduced, but this is at the expense of sensitivity, Generally, when the diameter of the probe is equal to the surface area of the measured body, the sensitivity is reduced to 70%, so when the sensitivity is not high, the measurement surface area can be appropriately reduced.

Requirements for the operating temperature.

Generally, the maximum temperature of imported eddy current sensors is not more than 180, and the domestic ones can only reach 120, and these data are the best manufacturers, which have great unreliability, according to the analysis of various relevant data, in fact, when the working temperature exceeds 70, the sensitivity of the eddy current sensor will be significantly reduced, and even cause damage to the sensor, in the nuclear power plant industry, turbine engine manufacturing, rocket launch, automobile engine inspection, Metallurgy, steel, furnaces and other fields must be resistant to high temperature eddy current sensors must be very resistant, it is reported that the British Zhenshang Group eddy current sensor design engineers have successfully developed such sensors that can withstand thousands of degrees Celsius. The sensitivity of the eddy current sensor is affected by the temperature, and the installation and use of the eddy current sensor in the shaft vibration measurement should be as far away from the vapor seal as possible, and only special high-temperature resistant sensors such as high and low temperature eddy current sensors can be used near the installation of the vapor seal.

Requirements for probe holders.

The eddy current sensor is installed on the fixed bracket, so the quality of the bracket directly determines the measurement effect, which requires that the bracket should have enough stiffness to increase the natural frequency, and the bracket is also stimulated by the natural vibration when the measured body vibrates at the same time, the data show that the natural frequency of the bracket should be at least 10 times the mechanical rotation speed, the bracket should be parallel to the tangential direction of the measured surface, and the sensor is vertically installed on the bracket, although the center line of the probe has no effect on the system characteristics when the vertical direction is deviated by 15° angle, However, it is still best to ensure that the sensor is perpendicular to the surface being measured.

Requirements for initial clearance.

Various types of eddy current sensors, all under a certain gap voltage value, its reading has a good linearity, so when installing the sensor, the appropriate initial clearance must be adjusted, the characteristics of each set of products will be tested, and the corresponding characteristic curve is drawn.