MR338 Encoder

MR338 Encoder

ZapFREE® MRI Safe Fiber Optic Absolute Position Sensor

The MR338 Series ZapFREE® Fiber Optic Absolute Position Sensor is an entirely passive, non-metallic absolute rotary encoder designed for use in Magnetic Resonance Imaging (MRI), nanomagenetic detection, EMC test labs, and similar applications where immunity and transparency to electromagnetic fields is required.

The MR330 system measures absolute angular position from 0° to 360° with 0.025° (14-bit) resolution and can track turns up to 4096 counts (12 bits). The remote MR330 Controller Module features multiple built-in interface for compatibility with industry standard motor drives, PLCs, and motion control systems.


Measurement Parameters
Measurement Range 0° to 360° (continuous)
Resolution 13 bits (8192 counts), 14 bits (13,950 counts, 0.025°)
Maximum RPM Maximum 2,500 rpm for position reading; Mechanical limit is 6,500 rpm
Mechanical Performance
Moment of Inertia 2.17E-06 kg*m2
Starting Torque 3.58E-04 N*m with Shaft Seal
Max Shaft Loads Axial 30 N (6.75 lbf), Radial 60 N (13.5 lbf)
System MTBF (ISO Method) L10 bearing life at 100% of max radial/axial load at 2500 rpm: 5.68E+05 hours

L10 bearing life at 10% of max radial/axial load at 2500 rpm: 1.22E+06 hours

MR Attributes ACR Guidance Document for Safe MR Practices
MRI Useage Zones MR338 sensor is designed for safe use in all MR Zones I-IV
Materials Used Non-metallic except for fiber optic connector end
Explosive Atmospheres Inherently Safe, Simple Mechanical Device
EX Classification Inherently safe, simple mechanical device when used with MR330 Controller IECEx Test Report (IECExTR) GB/CML/ExTR 16.0070/00
IEC Ex EPL Mb/Gb/Gc/Db/Dc
NEC Exempt
Environmental Performance
Temperature/Humidity Operating: -20° C to +65° C, Storage: -20° C to +65° C, 0%-95% RH (non-condensing)
Ingress Protection Y Shaft Seal Option = IP65

N Shaft Shield Only Option = IP40

Physical Attributes
Housing Dimension Ø 58mm x 80mm L (industry standard 58mm servo mount housing)

Specifications subject to change without notice


  • 7″ Servo Mount Package
  • R1 = 1:10 (Fine)
  • R2 = 10:1 (Medium)
  • R3 = 500:1 (Coarse)