Eddy current sensor

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Eddy current sensor


MJ-VR9800 Split type eddy current displacement sensor


Centrifugal pumps

Turbo compressors

Steam turbines

Fans and blowers


Electric motors

Gear boxes

Journal bearing machines

MJ-VR9800 Split type eddy current displacement sensor can measure the relative position of the measured object (must be a metal conductor) and the probe end. Because of its features of non contact measurement, long-term high working reliability, high sensitivity, strong anti-interference ability, fast response speed and no oil-water and other medium influence, it is often used for long-term real-time monitoring the shaft displacement, shaft vibration, shaft speed and other parameters of the large rotating machinery, then we can analyze the work condition and failure reason of the equipment, in order to protect the equipment and do predicting repair effectively. It can measure displacement, amplitude, speed, size, thickness, surface unevenness. Analysis on the theory of rotor dynamics and bearing science, the running state of large rotary machines mainly depends on its core-rotating shaft, and the proximity sensor can measure the condition of the shaft directly, the measurement result is reliable and credible.

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  • Description
  • Specifications
  • Parameter selection
  • Feature
  • Inquiry

Section 1  Brief Introduction 

 The leading science and technology of MJ-VR9800 Proximity Transducer System  :

1. " the best parameter matching of coil temperature stability" technology ensure a good stability of probe temperature;

2. using the new PPS engineering plastics through" two injection" technology to ensure the good sealing of the probe, dimensional stability and exchange ability, working temperature range expanded to -50℃


3. " deformation connection" technology, higher strength and reliability of probe;

4. " deep negative feedback stability resonant loop" technology, make the preamplifier stability reach (0.05%/℃,0.02%/year );

5. according to the American military standard design and produce, preamplifier can work continuously in the environment of -50+105℃;

6. Proximitor circuit adopts the fault-tolerant design to ensure that any wiring errors will not  make damage; 

7. Proximitor uses the latest electronic technology, power consumption is lower than 12mA;

8. The shell of the proximitor adopts die casting technology, high frequency socket concave, wiring terminal mosaic protection and engineering plastics insulated structure, in order to make the preamplifier more solid and more convenient to use and install.

9. Advanced phase frequency characteristics of the testing and control method of the proximity sensor makes MJ-VR9800 series products are in the international leading level in the dynamic characteristics.



 It is widely used for online monitoring and fault diagnosis of displacement, vibration, rotational speed, the oil film thickness of the steam turbine, hydraulic turbine, generators, blowers, compressors, gear boxes and other equipments in the industries of electric power, petrochemical, metallurgical and so on.

Typical application diagram 


Section 2  Probe Types and Specifications

A.The probe diameter selection

Diameter of the probe head(mm) Linear range(mm) the length of the probe head

☆ Choose Pipe diameter to ensure the linear range is greater than the maximum range of movement 20% above of the measured object, unless the measured surface area does not meet the requirements of the minimum specimen size or restrictions on installation space, should choose larger linear range.

B.Thread specification selection and common probe casing thread specification

☆ Thread specification allows other choice

 C. Installation options

   --Standard installation

Reverse installation 

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C. Installation options


Standard installation

( a ) usually use a sleeve fix it on the machine

(b) φ50 commonly used methods for probe



The cable side out


Select it when the installation of axial space is small, usually fix it with the clamping block 




Flange mounting


Select it when the installation of axial space is small, fix it with bolts



☆ Unless the machine external mounting bracket mounted probe or the installation space limit, usually select standard installation type probe.


D. No thread length selection


With 10 mm for the unit,

Minimum no thread length is 0mm 0 0,

Maximum no thread length is 250mm 2 5,

Incremental change is 10mm 0 1


☆ No thread part of the probe is for the convenience of installation; when use the screw to install, the appropriate length of the no thread part can reduce the need length for screwed into the screw hole.


E. Selection of the shell length 


With 10 mm for the unit,

Minimum shell length is 20mm  0 2,

Maximum shell length is 250mm 2 5,

Incremental change is 10mm 0 1


☆ The shell length of the probe depends on the distance between the mounted position and the measured surface.

F. Selection of the cable length


1 0: 1.0m 

5 0: 5.0m 

9 0: 9.0m

☆ Selection of the cable length should consider the distance between the measured surface and the installation position of the proximitor.When use the screw to install, recommend to select 05 (0.5m), 10 (1.0m), ensure that when swirl the probe, the probe cable can rotate with the probe together, it is not easy to break the cable. We need to select an extension cable, total length of the extension cable and the probe is 5m or 9m. Mounted a probe inside of the machine, choose a probe, the total length should ensure that the cable joint is outside of the machine to prevent the oil pollute joint.

K. Armored selection

" K" means cable with armor

☆ if probe cable without pipeline protection, recommend to choose armored probe, so that the cable is not easy to be damaged.

Selection of sample


Meaning: the probe diameter φ8, casing thread M10×1, standard installation, no thread length is 10mm,shell length is 50mm, cable length is 5m, without armor.

Section 3 Proximitor sensor specifications

A. Probe diameter selection


0 5 match φ5 probe,

0 8 match φ8 probe,

1 1 match φ11 probe,

2 5 match φ25 probe,

5 0 match φ50 probe.


B. Cable length selection

5 0 match 5m cable long probe,

9 0 match 9m cable long probe.

C. Output mode selection

V Negative voltage output ( -18Vdc-26Vdc power supply )

I 420mA current output ( +18Vdc+30Vdc power supply )

☆ The proximitor is calibrated according to 40CrMo steel when it leaves factory, if the measured material is not 40CrMo steel, please inform the measured material when make the order, we will calibrate it according to the designated material when it leaves factory.


☆ The negative voltage output signal is compatible with BN3300, 7200 series of the United States of America Bentley Nevada company and the German PHILIPS products of Germany,  4 ~ 20mA current output signal is suitable for the computer data acquisition system.

Probe: working temperature is -50+175°C ; temperature drift ≤0.05%/°C

Preamplifier: working temperature is -50+120°C ; temperature drift ≤0.05%/°C

Frequency response : 0 ~ 10kHz; amplitude frequency characteristics: when 1kHz, it is -1%; when 10kHz, it is -5%; phase frequency characteristics: when 1kHz, it is -1 degree; when 10kHz, it is -100 degree.

Output characteristics: 

1.a negative voltage output, 

Power supply: -18Vdc-24Vdc 

power consumption ≤ 12mA ( not including the output current )

2. 4 ~ 20mA current output 

Power supply: +18Vdc+30Vdc  

Power consumption ≤ 12mA ( not including the output current )


Selection of  the front end

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