ML33Y Integrated Eddy Current Displacement Sensor

Ⅰ、ML33Y Integrated eddy current sensor principle：

The principle of eddy current measurement belongs to an inductive measurement principle. The eddy current effect results from the energy of the oscillating circuit. Eddy currents need to be formed in a material that conducts electricity. An alternating current is introduced into the inner coil of the sensor probe to create a magnetic field around the probe coil. If a conductor is placed in this magnetic field, according to Faraday's law of electromagnetic induction, eddy currents will be excited within the conductor. According to Lenz's law, the direction of the eddy current magnetic field is opposite to the coil magnetic field, and this will change the impedance value of the coil inside the probe. The change in this impedance value is directly related to the distance between the coil and the object being measured. After the sensor probe is connected to the controller, the controller can obtain the change of voltage value from the sensor probe and calculate the corresponding distance value based on it. The principle of eddy current measurement can measure all conductive materials.

Because the eddy current can penetrate the insulator, even if the surface is covered with the insulator metal material, it can also be used as the measured object of the eddy current sensor. The unique coil winding design enables the compact shape of the sensor jizhi, while meeting the requirements of its operation in high temperature measurement environments.

Ⅱ、ML33Y Integrated Eddy current sensor Applications：

By measuring the relative position of the metal being measured and the probe end, the eddy current displacement sensor senses and processes the corresponding electrical signal output. The sensor can work reliably for a long time, has high sensitivity, strong anti-interference ability, non-contact measurement, fast response speed, and is not affected by oil and water and other media. It is widely used in long-term real-time monitoring of parameters such as shaft displacement, shaft vibration and shaft speed of large rotating machinery. And has been extended to satellite launch, material identification, weighing measurement, metal plate thickness measurement, material shape variables and other applications.

Ⅲ、ML33Y Integrated eddy current sensor Technical parameters：

Ⅳ、ML33Y Integrated eddy current sensor selection：

Ⅴ、ML33Y Integrated Eddy Current Sensor Mounting size：

Ⅵ、ML33Y Integrated Eddy current sensor installation：

1、The probe installation clearance requirements

    When installing the probe, the linear measurement range of the sensor and the change of the measured gap should be considered, and when the total change of the measured gap is close to the linear working range of the sensor, it is especially important to pay attention to (the linear range of the selected sensor should be greater than 15% of the measured gap when ordering the selection). Generally, when measuring vibration, the installation gap of the probe is set at the linear midpoint of the sensor; When measuring displacement, it is necessary to determine the setting of the installation gap according to which direction the displacement changes or the amount of change in which direction is larger. When the displacement changes away from the probe end, the installation gap should be set at the linear near end; Otherwise, it should be located at the linear far end.

2、Requirements for initial gap

 Various models of eddy current sensors, are in a certain gap voltage value of its reading has a better linearity, so in the installation of sensors must adjust the appropriate initial gap, each set of products will be characteristic test, draw the corresponding characteristic curve, engineering and technical personnel in the use of sensors must carefully study the matching verification certificate, Carefully analyze the characteristic curve to determine whether the sensor meets the gap to be measured, and generally the larger the diameter of the sensor, the larger the measured gap.

3、Requirements for the probe bracket

  The eddy current sensor is installed on the fixed support, so the quality of the support directly determines the measurement effect, which requires that the support should have sufficient stiffness to improve the natural vibration frequency, avoid or reduce the vibration of the support when the measured body is vibrating at the same time, the natural vibration frequency of the support should be at least 10 times the mechanical rotation speed, the support should be parallel to the tangent direction of the measured surface. The sensor is vertically mounted on the bracket, and although the center line of the probe has no effect on the system characteristics when the vertical direction is offset by 15°, it is best to ensure that the sensor is perpendicular to the measured surface.

4、The influence of the material to be measured on the sensor measurement results

 The characteristics of the sensor are related to the conductivity and permeability of the measured body. When the measured body is a magnetic conductive material (such as ordinary steel, structural steel, etc.), eddy current effect and magnetic effect exist at the same time, and the magnetic effect reacts on the eddy current effect, so that the eddy current effect is weakened, that is, the sensitivity of the sensor is reduced. When the measured body is a weak magnetic permeability material (such as copper, aluminum, alloy steel, etc.), due to the weak magnetic effect, the eddy current effect is relatively strong, so the sensor sensitivity is high.

Copper: 14.9V/mm

Aluminum: 14.0V/mm

Stainless steel (1Cr18Ni9Ti): 10.4V/mm

45 steel: 8.2V/mm

5、The influence of the surface processing status of the measured body on the sensor measurement results

  The surface finish of the measured body facing the probe also affects the measurement results! The non-smooth surface of the measured body will bring a large additional error in the actual measurement application, especially for vibration measurement, the error signal is superimposed with the actual vibration signal, and it is difficult to separate electrically, so the measured surface should be smooth and clean. There should be no defects such as nicks, holes, bumps, grooves, etc. (except for bumps or grooves specially installed for key phasers and speed measurements). Generally, the measured surface roughness of vibration measurement is required to be between 0.4um and 0.8um; For displacement measurement, the measured surface roughness is required to be between 0.4um and 1.6um. If this cannot be met, the surface to be measured needs to be refined or polished.

6、The influence of residual magnetic effect on the sensor

 The eddy current effect is mainly concentrated on the surface of the measured body. If the residual magnetic effect is formed during the processing, the characteristics of the sensor will be affected by uneven quenching, uneven hardness, uneven metallographic structure, and uneven crystalline structure. During vibration measurement, if the residual magnetic effect on the surface of the measured body is too large, the measurement waveform will be distorted.

7、The influence of the surface size of the measured body on the sensor

  The range of magnetic field generated by the probe coil is certain, and the eddy current field formed on the surface of the measured body is also certain. In this way, there are certain requirements for the surface size of the measured body. In order to prevent the magnetic field generated by the eddy current from affecting the normal output of the instrument, a certain range of non-conductive media space must be left around the sensor head when installed, if more than two sensors are installed at the same time in a certain part, it is necessary to consider whether cross interference will occur, and the specified distance between the two probes must be maintained.

8、The influence of the surface coating of the measured body on the sensor

  The influence of the coating on the surface of the measured body on the sensor is equivalent to changing the material of the measured body. Depending on the material and thickness of the coating, the sensitivity of the sensor will change slightly.

9、The influence of high-frequency coaxial cable on the sensor

  High frequency coaxial cable is also a major factor affecting the electrical performance of eddy current sensors. Because the sensor works in a high frequency state (oscillation frequency about 1MHZ), the frequency attenuation, temperature characteristics, impedance, length, etc. of the high frequency coaxial cable have become factors affecting the performance of the sensor.

10、The influence of external magnetic field on the sensor

  Eddy current sensor is an inductive sensor, because its main principle is the eddy current effect, so the influence of external magnetic field should be fully considered in engineering applications! Strong external magnetic field will definitely affect the performance of the sensor.

  For the external static magnetic field, because the strength of the static magnetic field is certain, the direction and eddy current magnetic field may present various conditions, and once the direction of the external static magnetic field is determined, its interference with the eddy current magnetic field is also certain. Therefore, in practical engineering applications, the influence of static magnetic field can measure the change of sensor sensitivity through field tests and eliminate it through subsequent circuits or software algorithms.

  For external alternating magnetic fields, such as large exciter, frequently started large motor, starter, etc., the direction and strength of the magnetic field may not be a definite value, so the amount generated needs to keep the eddy current sensor away from the range of the alternating magnetic field, or take magnetic field shielding measures to minimize the impact.

Ⅶ、Acceptance and storage of eddy current:

One .Acceptance check

1.Remove all parts of the system from the packing box. Check for any damage caused by improper transportation. If so, it shall immediately negotiate with the carrier to lodge a claim and report the situation to the company.

2.Check the order and packing list to check whether the goods are complete, product model specifications are correct. If it is a complete order, the system is connected, and the power is switched on to check whether the static characteristics of the system comply with the indicators indicated in the factory verification list, usually these indicators should be in accordance with the technical specifications specified in the appendix or the agreed technical agreement.

3. If the product is in good condition, and not immediately installed and used, it is best to carefully put all parts back into the original packaging box, sealed and stored for future use.

4、If the acceptance is not qualified, please contact the company as soon as possible.

two. storage

 If not used for a long time, the sensor system should be stored in a clean room where the temperature is between -30 ° C and 70 ° C and the relative humidity is not greater than 90%, and the indoor air must not contain corrosive gases. If the storage period is more than one year, it should be newly calibrated before use.

Three. Specimen material

Unless specifically stated at the time of ordering, the sensor system is usually calibrated using 40CrMO material samples before leaving the factory, and only the material of the tested body of the same series can produce the characteristic equation similar to that of 40CrMO; When the material of the tested body is very different or completely different from the 40CrMO composition, please explain or provide a sample of the tested body material when ordering.