Robust Eddy Current Displacement Sensors Resistant to Oil and Dirt

Micro-Epsilon offers eddy current displacement sensors which occupy a special position within inductive displacement sensors. These sensors are not affected by environmental influences such as temperature, pressure and dirt; and they measure displacement, distance and position with high accuracy. Our compact eddyNCDT 3001 range now offers greater measuring ranges, opening up new application areas.

Micro-Epsilon’s eddy current sensors are an individual in the market of inductive measuring techniques. They provide accurate and precise measurement results even under harsh industrial environments. Measurements from eddy currents utilize the extraction of energy from an oscillating circuit. This energy is required for the induction of eddy currents in electrically-conductive materials. In these measurements, an alternating current coil is placed, causing a magnetic field to form around the coil. When an electrically conducting object is introduced to the magnetic field, eddy currents become induced and form a field relative to Faraday‘s induction law. This field acts against the field of the coil and causes a change in the impedance of the coil. The controller can calculate the impedance by measuring the change in the amplitude and phase position of the sensor coil.

This principle can be used to measure the electrically conductive of all materials. Micro-Epsilon sensors possess a special coil wrapping creating a very compact sensor design that can still be used across high temperature ranges. Eddy currents penetrate insulating materials and metals behind an insulating layer can even be used as the object of measurement. Even dust, dirt and oil do not have any effect on the measurement. Combining this immunity with the sensor’s robust temperature-resistant design enables highly precise measurements under strenuous industrial environments.

Eddy current sensors provide a "clean performance" in dirty conditions

Eddy current sensors provide a "clean performance" in dirty conditions

Inductive Sensors Based on Eddy Currents Now Offer even more Flexibility

The eddyNCDT 3001 series is specifically designed for applications where standard inductive displacement sensors are stretched beyond their performance limits. Their compact size has only previously been seen in inductive sensors and proximity sensors. This compact sensor stands out due to its ease of operation. The eddyNCDT 3001 eddy current sensors not only possesses an M12 housing but are now also available with an M18 housing covering measurement ranges of to 2 mm to 8 mm. These ranges now open new application areas. The sensors are protected to IP67 and are usable across automation, machine building and machine design applications. Moreover, these sensors possess a temperature-compensation of up to 70 °C. These sensors are easy to use and give an excellent price to performance ratio, making them particularly suitable for high volume, OEM applications and for salt water in offshore/marine applications. The excellent measurement accuracy, linearity and high frequency response rate of 5 kHz are outstanding characteristics compared to conventional inductive sensors in the same price range. EddyNCDT sensors are factory-calibrated for ferromagnetic and non-ferromagnetic objects, such as aluminum and steel. Customizable adaption to other materials is also possible.

Oil Gap in Hydrostatic Bearings

Eddy current displacement sensors are often used in large plant and machinery, such as stone mills or telescopic installations which usually operate using hydrostatic bearings. These bearing systems are constantly supplied with liquid lubricant through an external pressure supply. The lubricant is squeezed between the bearing surfaces. Therefore, they are always separated from each another by a thin film of lubricant. The bearing surfaces operate without wear because they are not exposed to any friction. This enables a positional control on the sub-micrometer level. Any changes in the hydraulics or pressure drops can have serious consequences and can result in wear to the bearings and system failure.

This can lead to high maintenance and repair costs. Therefore, the oil gap in hydrostatic bearings must always be inspected regularly. This is possible using the eddyNCDT 3001 eddy current sensor. The compact sensor is placed horizontally to the bearing shoe, so that it is not exposed to oil pressure in the bearing. Instead, it measures through the oil film onto the opposite bearing surface. It is easy to install eddyNCDT 3001 sensors, so are they suitable for aging plants that require retrofitting.

Inspection of the oil gap in hydrostatic bearings using eddy current eddyNCDT 3001 sensors.

Inspection of the oil gap in hydrostatic bearings using eddy current eddyNCDT 3001 sensors.

The eddyNCDT 3005 has been developed by Micro-Epsilon for integration into various plants and machineries. The eddyNCDT 3005 is a novel, powerful eddy current measurement device for fast and high precision displacement measurements. Aside from providing an ease of use and high measurement accuracy, it also offers an excellent price to performance ratio. Therefore, this sensor is typically suited for OEM integration and mechanical engineering applications. The system comprises of a compact M12 controller, a sensor and an integrated cable. It is also factory-calibrated for ferromagnetic or non-ferromagnetic materials. Our eddyNCDT 3005 sensors and controller compensate for temperature, which is why high temperature measurement accuracies can be achieved, even under fluctuating temperatures.

Maximum signal stability thanks to active temperature compensation.

Maximum signal stability thanks to active temperature compensation.

These sensors are designed for ambient temperatures up to a maximum of 125 °C, but they can be custom engineered for temperatures ranging from -30 °C to 180 °C, if the user wishes. The measurement system is also resistant to up to 10 bar of pressure. Customer-specific designs can also be tailored to suit individual requirements in high volume orders.

Unconditional Precision

EddyNCDT sensors offer exceptionally precise measurements and can be used when micron accuracies are required. The can also be used at ambient temperatures ranging from -40 °C to more than 200 °C, making the eddy current displacement sensors robust against large temperature fluctuations.

This information has been sourced, reviewed and adapted from materials provided by Micro Epsilon.

For more information on this source, please visit Micro Epsilon.

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