ML33YD Integrated Eddy Current Displacement Sensor

Ⅰ. ML33YD integrated eddy current displacement sensor working principle:

The eddy current measuring principle is an inductive measuring principle. The eddy current effect results from the energy of an oscillating circuit. Eddy currents can only be formed in electrically conductive materials. By introducing an alternating current into the coil inside the sensor probe, a magnetic field is formed around the probe coil. If a conductor is placed into this magnetic field, eddy currents are excited in the conductor according to Faraday's law of electromagnetic induction. According to Franz's law, the direction of the eddy currents is opposite to the magnetic field of the coil, and this changes the impedance of the coil inside the probe. This change in impedance is directly related to the distance from the coil to the object being measured. When the sensor probe is connected to the controller, the controller can obtain the change in voltage value from the sensor probe and, based on this, calculate the corresponding distance value. The eddy current measuring principle can be used to measure all electrically conductive materials. Because eddy currents can penetrate insulators, even metal materials covered with insulators can be used as eddy current sensors. The unique coil winding design enables the sensor to be operated in high temperature measurement environments while achieving a jizhi compact profile.

Ⅱ、ML33YD integrated eddy current displacement sensor technical parameters:

Ⅲ、ML33YD integrated eddy current displacement sensor selection:

Ⅳ、Installation dimensions of ML33YD integrated eddy current displacement sensor:

Ⅴ、ML33YD Integrated Eddy Current Displacement Sensor is installed and used：

1、Requirements for the probe mounting clearance

     When installing the probe, the linear measurement range of the sensor should be considered and the amount of change in the measured gap, when the total amount of change in the measured gap is close to the linear operating range of the sensor, in particular, attention should be paid to (in the order selection should be made to select the linear range of the sensor is greater than 15 per cent or more of the measured gap). Usually, when measuring vibration, the probe mounting gap is set at the linear midpoint of the sensor; when measuring displacement, according to the displacement to which direction or to which direction of the change in the amount of the larger to determine the mounting gap setting. When the displacement changes in the direction away from the end of the probe, the mounting gap should be set at the linear proximal end; conversely, it should be set at the linear distal end.

2、Requirements for the initial clearance

Various types of eddy current sensors, are in a certain gap voltage value of its readings have a better linearity, so in the installation of the sensor must be adjusted to the appropriate initial gap, for each set of products will be characteristics of the test, drawing the corresponding characteristic curve, engineers and technicians in the use of sensors must be carefully studied supporting the certificate of calibration, and carefully analyse the characteristic curve, to determine whether the sensor Meet the gap to be measured, generally the larger the diameter of the sensor to measure the gap is also larger.

3、Requirements for the probe stent

Eddy current sensor is mounted on a fixed bracket, so the bracket is good or bad directly determines the effect of measurement, which requires that the bracket should have enough stiffness to improve the self-oscillation frequency, to avoid or reduce the vibration of the measured body when the bracket is also excited by self-oscillation at the same time, the bracket's self-oscillation frequency should be at least 10 times the mechanical rotational speed, the bracket should be parallel to the tangent direction of the surface to be measured, the sensor is mounted perpendicularly on the bracket, although the probe's The sensor is mounted vertically on the bracket, although the centre line of the probe has no effect on the characteristics of the system when it is offset from the vertical by an angle of 15°, it is best to ensure that the sensor is perpendicular to the surface being measured.

4、Effect of the subject material on the sensor measurements

Sensor characteristics and the conductivity of the body to be measured magnetic permeability related, when the body to be measured for the permeability of the material (such as ordinary steel, structural steel, etc.), due to eddy current effect and magnetic effect at the same time, and the magnetic effect of the counter-action on the eddy current effect, so that the eddy current effect is weakened, i.e., the sensor's sensitivity is reduced. When the measured body is weakly magnetically conductive material (such as copper, aluminium, alloy steel, etc.), due to the weak magnetic effect, the eddy current effect is relatively strong, so the sensor induction sensitivity is higher.

              Copper: 14.9V/mm

              Aluminium: 14.0V/mm

              Stainless steel (1Cr18Ni9Ti): 10.4V/mm

              45 steel: 8.2V/mm

              40CrMo steel: 8.0V/mm

5、The influence of surface processing of the body on sensor measurements

The surface finish of the DUT directly in front of the probe also affects the measurement results! The surface of the measured body is not smooth, in the actual measurement application will bring a large additional error, especially for vibration measurement, the error signal and the actual vibration signal superposition together, and is difficult to separate electrically, so the measured surface should be smooth, there should be no scratches, holes, bumps, grooves, and other defects (for the purpose of keying the phase, rotational speed measurement set up for the exception of the bumps or grooves). Generally, for vibration measurement, the roughness of the measured surface is required to be between 0.4um and 0.8um; for displacement measurement, the roughness of the measured surface is required to be between 0.4um and 1.6um. If it cannot be satisfied, it is necessary to carry out diffraction grinding or polishing on the measured surface.

6、The influence of the residual magnetic effect on the sensor of the tested body surface

The eddy current effect is mainly concentrated on the surface of the measured body, if the residual magnetic effect is formed due to processing, as well as uneven quenching, uneven hardness, uneven metallurgical organisation, uneven crystalline structure, etc. will affect the sensor characteristics. In vibration measurement, if the residual magnetic effect on the surface of the measured body is too large, the measurement waveform will be distorted.

7、Effect of the measured body surface size on the sensor

As the magnetic field generated by the probe coil is of a certain range, the eddy current field formed on the surface of the measured body is also of a certain size. This requires a certain size of the surface of the body to be measured. In order to prevent the magnetic field generated by eddy currents affect the normal output of the instrument when the installation of the sensor head must leave a certain range of non-conductive media around the space, if in a certain part of the installation of more than two sensors at the same time, it must be considered whether it will produce cross-interference between the two probes must be to maintain the required distance.

 Usually, when the surface of the body to be measured is a plane, to the point directly opposite the probe centre line as the centre, the diameter of the surface to be measured should be greater than the probe head diameter of more than 1.5 times; when the body to be measured is a circular axis and the probe centre line and the axis of the line orthogonal to the general requirements of the diameter of the measured axis of more than three times the diameter of the head of the probe, or else the sensor's sensitivity will decline, the smaller the surface of the body to be measured, the more the sensitivity decreases. The smaller the surface of the body under test, the more the sensitivity drops. When the surface size of the body under test is the same as the probe head diameter, the sensitivity will drop to about 72%. The thickness of the measured body also affects the measurement results. The depth of eddy current field action in the measured body is determined by the frequency, material conductivity, and magnetic permeability. Therefore, if the measured body is too thin, will cause the eddy current effect is not enough, so that the sensor sensitivity decreases, the general requirements of the thickness of more than 0.1mm above the steel and other magnetically conductive materials and thickness of more than 0.05mm above the copper, aluminium and other weakly conductive materials, the sensitivity will not be affected by the thickness of the impact of its.

8、Effect of the tested body surface coating on the sensor

The effect of the plating on the surface of the measured body on the sensor is equivalent to changing the material of the measured body, depending on the material, thickness of the plating, the sensitivity of the sensor will change slightly.

9、Effect of the high-frequency coaxial cable on the sensor

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

10、Effect of the external magnetic field on the sensor

Eddy current sensor belongs to the inductive sensor, because its main principle of action is the eddy current effect, so the influence of the external magnetic field in the engineering application should be fully considered! Strong external magnetic field will certainly affect the performance of the sensor.

For the external static magnetic field, because the static magnetic field strength is certain, the direction and the eddy current magnetic field may present a variety of 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 the actual engineering applications, the effect of static magnetic field can be measured through the field of the test changes in the sensor sensitivity, through the subsequent circuit or software algorithms to exclude.

For external alternating magnetic fields, such as large exciters, large motors with frequent start-ups, starters, etc., the direction and strength of the magnetic field may not be a certain value, and thus the amount of its generation needs to keep the eddy current sensor away from the scope of action of the alternating magnetic field, or to take magnetic field shielding measures so as to minimise the impact of the generation.

Ⅵ、Acceptance and storage of eddy current displacement sensor

ⅰ. Acceptance

1、Remove the system parts from the box. Check whether there is any damage caused by improper transport. If there is, immediately take up the matter with the carrier to file a claim and refer the situation to our company.

2、Check against the order form and packing list that the goods are complete and that the product type and specification are correct. If the order is for a complete set, connect the system and power it up to check that the static characteristics of the system are in accordance with the specifications stated in the factory calibration sheet, which should normally be in accordance with the technical specifications set out in the appendices or the agreed technical agreement.

3、If the product is intact and is not to be installed and used immediately, it is best to place the parts carefully back into the original box, seal it and store it for future use.

4、If the acceptance fails, please contact us as soon as possible.

ⅱ．Storage

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

ⅲ．Material for test

Unless otherwise specified at the time of ordering, the sensor system is normally calibrated at the factory using a 45 gauge steel specimen, which produces characteristic equations similar to those of 45 gauge steel only if the DUT material is of the same series; when the DUT material is of a very different or completely different composition from 45 gauge steel, please specify or provide a sample of the DUT material at the time of ordering.