Eddy Current Position Sensors

Inductance Gabe Poehls Eddy current position sensors rely on the principle of inductance to determine the proximity of a sensor coil to a conductive Summer Research target. Inductance is a result of the Blue Line Engineering specializes in the interaction between magnetic fields and design and fabrication of high precision electrical current within a coil of wire. eddy current position sensors for Faraday’s Law and Lenz’s Law describe various aerospace applications, typically this interaction: used on fast steering mirrors for laser communication. This summer we -An electromotive force Eddy Currents worked on developing a modeling (EMF) is generated within in process for their line of sensor coils to a closed loop equal to the Eddy currents are loops of electrical current induced within aid in new position sensor development. rate of change in magnetic conductors as a result of a changing magnetic field. These Michael Faraday flux through the loop. currents circulate such that a new magnetic field is created to oppose the field that created them. This relationship is -This EMF causes a current to shown in the following diagram: flow through the loop and a magnetic field is formed which opposes the field that caused it. Emil Lenz

Deriving Self Inductance ANSYS Maxwell Software used to model coil sensors and perform E&M analysis with an aluminum target (not shown) and collect inductance data

A changing magnetic field is generated in the sensor coil when supplied by an AC Voltage source. As the target approaches the sensor coil, eddy currents are formed within the body of the aluminum target which create a magnetic field of their own to oppose that of the coil. This decreases the net magnetic flux through the coil and with it the Inductance vs. Position for physical test data (red) and ANSYS model data (blue). As the target approaches the sensor (the zero of the x- measured inductance of the circuit. By measuring axis) the inductance of the sensor coil circuit is shown to decrease

inductance at various coil-target distances, a relationship Image References: Self Inductance: Image #1: https://en.wikipedia.org/wiki/Emil_Lenz between inductance and target position can be determined. Image #2: https://en.wikipedia.org/wiki/Michael_Faraday Image #3: https://www.bluelineengineering.com/