MR344 Hollow Shaft Encoder

MR344 Hollow Shaft Encoder

ZapFREE® Hollow Shaft Fiber Optic Incremental Encoder

The MR344 ZapFREE® Heavy Duty Hollow Shaft Fiber Optic Incremental Sensor is an entirely passive, intrinsically safe, fiber optic incremental rotary encoder – ideal for a wide range of harsh and hazardous environmental applications. The passive, all-optical sensor connects to the remote controller via a standard duplex 62.5/125 multimode optical fiber link.

The remote MR340 Controller Module transmits and converts optical signals to/from the sensor. The Controller’s multiple built-in interfaces insure compatibility with industry standard motor drives, PLCs, quadrature counters and motion control systems.


Measurement Parameters
Resolution 1024ppr
Max Speed

3,000 RPM continuous (MR320 Quadrature Outputs and Analog Outputs activated ONLY)

3,600 RPM short term (< 1 minute)

(NOTE: At 3,000 RPM, MR344 housing temperature rises by 25°C above ambient due to bearing friction. Environmental temperature must be reduced accordingly. There is also a trade-off between operating speed and use of the MR340 auxiliary functions (analog outputs, divider, multiplier, etc.). Contact Micronor to discuss your requirements.

Mechanical Parameters
Moment of Inertia 2.06E-4 kg*m. (Pocket Hole version), 2.09E-4 kg*m. (Through Hole version)
Starting Torque 3.53E-3 N*m (Pocket Hole version)
System MTBF L10 Bearing life calculated at 2500 RPM: 2.12E+07 hours (2411 years)
Optical Interface
Optical Interface LC Duplex, 62.5/125μm Graded Index Fiber, 0.275NA, Type OM1
Link Length Up to 2000 meters with MR340 Controller
Explosive Atmospheres Inherently Safe, Simple Mechanical Device
EX Classification Inherently safe, simple mechanical device when used with MR340 Controller
Environmental Attributes

Standard: -40°C to +80°C, 0%-95% RH (non-condensing)

Extended: -60°C to +125°C, 0%-95% RH (non-condensing)

Ingress Protection

Through Hole Version=IP54 (dust protected, protected against splashing water)

Pocket Hole Version=IP66 (dust proof, protected against powerful water jets)

Physical Attributes
Housing Dimension Ø 100mm x 49mm
Unit Weight 655 g (23 oz)
Materials Body: Anodized Aluminum; Shaft Clamp and Bearings: Stainless Steel

Specifications subject to change without notice


  • 100% passive sensing design – no electronics whatsoever
  • Sensor can be installed in all manner of  hazardous locations and potentially explosive atmospheres – mines, gas and dust
  • Immune to EMI and RFI for safe use in and around medical equipment, VFD drives and other “noisy” industrial environments
  • Immune to lightning and high voltage which “zaps” electronics-based encoders
  • Outdistances copper, link lengths to 2000m
  • Standard Temperature range: -40°C to +80°C;
  • Extended Temperature option: -60°C to +125°C
  • Special versions can be engineered for radiation and thermal-vac environments

Ordering Information

MR344-F38XYYYZ Where X=Bore/IP Option, strong>YYY=Optical Interface, Z=Temperature Range
X Options: (Blank)=Through Hole-IP54, P=Pocket Hole-IP66
YYY Options: C1R5=1.5m Pigtail , C03=3m Pigtail
Z Options: (Blank)=Standard -40°C to +80°C, E=Extended -60°C to +125°C
MR344-99-XX Shaft Adapters, where XX=Shaft OD Option
For 8mm, order MR344-99-01
For 10mm, order MR344-99-02
For 12mm, order MR344-99-03
For 14mm, order MR344-99-04
For 15mm, order MR344-99-05
For 16mm, order MR344-99-06
For 18mm, order MR344-99-07
For 20mm, order MR344-99-08
For 25mm, order MR344-99-09
For 30mm, order MR344-99-10
For 32mm, order MR344-99-11
For 0.5″, order MR344-99-12
For 0.625″, order MR344-99-13
For 0.75″, order MR344-99-14
For 1″, order MR344-99-15
For 1.25″, order MR344-99-16
MR314A Long Tether Arm Kit
MR340-1 DIN Rail Mount Controller


Quick Ship Configurations

MR340-0 OEM PCB Controller
MR340-1 DIN Rail Mount Controller
MR344-F38C1R5 Hollow Shaft Encoder, 1024ppr, Though Hole, IP54, 1.5mm Pigtail
MR344-F38PC1R5 Hollow Shaft Encoder, 1024ppr, Pocket Hole, IP66, 1.5m Pigtail

Shaft Adapter, For 12mm OD ShaftShaft Adapter, For 15mm OD Shaft
Shaft Adapter, For 0.5″ OD Shaft
Shaft Adapter, For 0.625″ OD Shaft
Shaft Adapter, For 0.75″ OD Shaft
Shaft Adapter, For 1″ OD Shaft

MR314A Long Tether Arm Kit