MRI safe linear encoder delivers 100µm resolution

June 19, 2015 // By Julien Happich
Micronor has introduced what the company claims to be the world's first commercially-available MRI Safe linear position sensor system for OEM motion control applications. With 100µm resolution and 50µm accuracy, the MR303 linear sensor is suitable for medical, MRI, robotic and industrial applications where position and speed must be precisely monitored, and electromagnetic immunity and invisibility is required.

The sensor works in conjunction with the MR302-2 OEM Controller which enables the sensor to integrate with conventional PLC controllers and servo drives.

The position sensor is immune to any electromagnetic interference, such as magnetic fields, lightning, high voltage and radiation. Being fabricated from non-ferrous and non-metallic materials, the sensor is also completely transparent to electromagnetic fields. The sensor’s magnetic invisibility also makes it the ideal position sensor for use in Super Paramagnetic Relaxation Measurements in which extremely small magnetic fields are measured. These attributes allow the MR303 sensor to be safely used in and around the MRI bore and does not produce any imaging artefacts.

The fiber optic linear incremental encoder system is based on an innovative optical technique embodied in Micronor’s U.S. Patent 7,196,720 in which an electrically passive, all-optical sensor and remote controller are interconnected via a duplex fiber optic link. The system uses a coarse wavelength division multiplexing technique incorporating two lasers representing the A and B quadrature signals. An encoder film strip passes through the MR303 optical read head, modulating the A and B optical signals. The remote MR302-2 Controller provides both the optical input to the MR303 Sensor and processes the modulated optical return signal.

The MR302-2 Controller features both A/B quadrature outputs and Modbus RTU serial interface for transparent integration into the user’s application. A discrete HOMING Input is used for internally pre-setting the absolute position while a discrete STATUS Output provides the direct means of monitoring the encoder’s system health. The controller contains a feature-rich Modbus communications protocol for ease of integration into the user’s control system.

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