How to install the eddy current sensor?
It is understood that the eddy current sensor can measure the distance between the measured metal conductor and the probe surface statically and dynamically non-contact, high linearity, and high resolution. It is a non-contact linear measurement tool. The eddy current sensor can accurately measure the static and dynamic relative displacement changes between the measured body (must be a metal conductor) and the end face of the probe. Installation method of eddy current sensor
1. Probe installation
1.Before inserting the probe into the mounting hole, make sure that there is no debris in the hole and that the probe can rotate freely without being entangled with the wire.
2.In order to avoid scratching the end of the probe or the monitoring surface, the gap of the probe can be measured with a non-metallic feeler gauge.
3.The electric vapor method of connecting the probe lead to the extension cable and proximitor can also be used to adjust the probe gap.
When the probe gap is adjusted properly, tighten the lock nut. At this time, it should be noted that over tightening will damage the threads. After the probe is fixed, the lead wire of the probe should also be firm. The length of the extension cable should be the same as the length required by the Proximitor. Any lengthening or shortening will cause measurement errors. The specific installation is shown in Figure 1.
When each measuring point needs to install two sensor probes at the same time, the two probes should be installed on the same plane on both sides of the bearing 90°±5° apart. Since the bearing cover is generally divided horizontally, the two probes are usually installed at 45° on each side of the vertical centerline. From the end of the prime mover, they are defined as X probe (horizontal direction) and Y probe (vertical direction). The X direction is to the right of the vertical centerline, and the Y direction is to the left of the vertical centerline. as shown in picture 2.
2. Installation of extension cable
The extension cable is an important part of the eddy current sensor as the middle part connecting the probe and the Proximitor. Therefore, the installation of the extension cable should ensure that it is not easily damaged during use, and the high temperature environment of the extension cable should be avoided. The connection between the probe and the extension cable should be locked, and the connector should be wrapped with a heat-shrinkable tube to avoid grounding and prevent the connector from loosening. When laying the extension cable, avoid that the laying radius is too small and the cable will be damaged. Generally, the diameter of the extension cable reel shall not be less than 55mm.
3. Proximitor installation
The Proximitor should be placed in a cast aluminum box to avoid mechanical damage and contamination. Excess cables are not allowed to be attached to the box. Without changing the length of the cable from the probe to the Proximitor, multiple Proximitors are allowed in the same box to reduce installation costs and simplify the process from the Proximitor to the monitor. Cable routing. Use proper isolation and shielding to ground to minimize the interference on the signal. The Proximitor is the signal processing part of the entire sensor system. It is required to be installed in a place far away from the high-temperature environment. The surrounding environment should be free of obvious steam and water droplets, non-corrosive vapor, dry, low vibration, and Proximitor A place where the ambient temperature is not much different from the room temperature. During installation, the metal part of the Proximitor housing should not be in contact with the housing or the ground. During installation, other interference signals must be avoided to affect the measurement circuit.
4. Locking the installation gap of 4-axis vibration sensor
Connect the probe, extension cable, and proximitor, and connect the power supply to the sensor system, monitor the output voltage of the proximitor with a high-precision multimeter, and adjust the gap between the probe and the measured surface, and the output voltage of the current amplifier When it is between 10-11vDC, tighten the two fastening nuts of the probe to fix the probe.
5. matters needing attention
1.Irregular surface of the measured object will bring additional errors to the actual measurement. Therefore, the surface of the measured object should be flat and smooth, and there should be no protrusions, holes, nicks, grooves and other defects.
2.When the measured body is a circular axis and the probe center line is orthogonal to the axis line, the diameter of the measured shaft is generally required to be more than 3 times the diameter of the probe head.
3.There should be no scars, small holes and gaps on the surface of the tested body, and surface plating is not allowed. The material of the tested body should be the same as the material calibrated by the probe and proximitor.
4.The probe is fixed on the bearing seat by a bracket. The bracket should have sufficient rigidity to increase its natural frequency and avoid or reduce the excited natural vibration of the bracket when the measured body vibrates.
5.Requirements for initial clearance
The eddy current sensor should have a good linearity under a certain gap voltage (the gap between the top of the sensor and the measured object, which is generally the voltage indicated on the meter) value, so the reading must be adjusted properly when installing the sensor The initial gap.
After the rotor rotates and the unit is loaded, the rotor will be displaced relative to the sensor. If the sensor is installed on the top of the bearing, the gap will be reduced; if installed in the horizontal direction of the bearing, the gap depends on the direction of rotation of the rotor; when the steering is constant, the gap depends on whether it is installed on the right or left. In order to obtain a suitable working clearance value, the shaft journal displacement value and displacement direction of the unit after load from the static state to the rotating state of the rotor should be estimated during installation, so as to be considered when adjusting the initial clearance. According to field experience, the shaft journal elevation of the rotor from static to working speed is about 1/2 of the bearing gap; the horizontal displacement is related to the bearing form, the gap on both sides of the bearing and the working status of the unit sliding pin system. The general displacement value is 0.05- 0.20mm.
When adjusting the initial gap of the sensor, in addition to the above factors, the maximum vibration value and the original rotor sway value should also be considered. The initial gap of the sensor should be greater than the maximum possible amplitude of the shaft and 1/2 of the original sway value of the shaft.
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