EC-TD5325 Cradle Position Sensor System

EC-TD5325 Cradle Position Sensor System

ZapFREE® MRI Safe Cradle Position System (Gold Standard)

The position of the patient cradle within an MRI machine must be accurately measured and verified to the standard built-in position measuring system. The EC-TD5325 uses the Micronor MR338 MRI Safe (non-metallic) Absolute Position Sensor to calibrate and verify the accuracy of the factory-installed system.

The all-optical MRI safe position sensor is coupled to a purpose-built accurate pull string mechanism which measures the pay-out of a film strip that is attached to the cradle. One end of the film is secured to the cradle while the far end of the string is wound up on a drum. When the cradle moves, the film is either pulled from the drum, or retracted onto the drum. The measurement is made by a precision pulley attached to the MR338 absolute position sensor. The pulley is a sprocket wheel that engages into the sprocket holes of the film, preventing slippage over the measuring wheel. Any small minute change in film pay-out is registered as a change in distance to the cradle.

The EC-TD5325 system is supplied with CMS, a PC software package used to capture, monitor and analyze the position of the cradle within an MRI machine. The CMS derives the position information from the MICRONOR MR338 MRI Safe Fiber Optic Absolute Sensor. During a capture sequence, it continuously monitors and logs in real-time the position at a predetermined time interval. The acquisition timing is controlled by the sensor controller (MR330) and uses a quartz crystal for accuracy to within 100ppm. The high resolution and fast update rate of the sensor makes it possible to derive accurate velocity and acceleration information from the position signal.

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Measurement Parameters
Maximum Payout 4000 mm (4m)
Repeatability ±0.05mm (Std Dev)
Accuracy ±0.15mm (Std Dev)
Speed 500 mm/s
Acceleration 250 mm/s²

Specifications subject to change without notice


  • Medical
  • MRI
  • Robotics
  • Industrial


  • 100% passive optical sensor
  • MRI safe design
  • Immune to EMI, RFI, lightning and ground loops
  • Immune and invisible to magnetic fields
  • Inherently Safe, Simple Mechanical Device
  • Supplied with Cradle Monitoring Software package