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 medium space must be left around the sensor head during installation. If more than two sensors are to be installed at a certain position at the same time, it is necessary to consider whether there will be cross interference, and a specified distance must be kept between the two probes. The surface area of the measured object should be more than three times the diameter of the probe, and it can be appropriately reduced if it cannot meet the requirements of three times, but this is at the expense of sensitivity. Generally, when the diameter of the probe is equal to the surface area of the measured object,
Working temperature requirements
The highest temperature of imported eddy current sensors is generally not higher than 180℃, while the highest temperature of domestic eddy current sensors can only reach 120℃, and these data are all from manufacturers, which is very unreliable. According to the analysis of various related data, in fact, when the working temperature exceeds 70℃, the sensitivity of eddy current sensor will be obviously reduced, and even the sensor will be damaged. Eddy current sensors necessary for high temperature resistance in nuclear power plant industry, turbine engine manufacturing, rocket launch, automobile engine detection, metallurgical steelmaking furnace and other fields must have high tolerance. It is reported that some group eddy current sensor design engineers in Britain have successfully developed this sensor which can withstand thousands of degrees Celsius. The sensitivity of eddy current sensor is affected by temperature. When installing and using eddy current sensor in shaft vibration measurement, it should be as far away from the seal as possible. Only special high temperature sensors, such as high and low temperature eddy current sensors, can be installed near the seal.
Requirements for probe bracket
The eddy current sensor is installed on the fixed bracket, so the quality of the bracket directly determines the measurement effect, which requires the bracket to have enough stiffness to improve the natural vibration frequency to avoid or reduce the natural vibration of the bracket when the measured object vibrates. The data show that the natural vibration frequency of the bracket should be at least 10 times of the mechanical speed, the bracket should be parallel to the tangent direction of the measured surface, and the sensor should be installed vertically on the bracket, although the center line of the probe is 10 in the vertical direction.
Requirements for initial permission
Various types of eddy current sensors have good linearity only under a certain gap voltage value, so when installing the sensor, it is necessary to adjust the appropriate initial gap, conduct a characteristic test on each set of products, and draw the corresponding characteristic curve. When using the sensor, engineers and technicians must carefully study the matching calibration certificate and analyze the characteristic curve to determine whether the sensor meets the gap to be measured. Generally, the larger the diameter of the sensor, the larger the gap to be measured.