Hettich EBA 200: rotor imbalance protection out of action after misuse
What happened
The unit had been damaged by improper operation, and the rotor imbalance detection was in doubt; suspicion fell on the imbalance sensing assembly.
What was checked
- Checked the magnetic imbalance sensor of the rotor, including whether its magnet had come loose from its seat.
- Examined the sensor signal at the input IC with an oscilloscope to identify the sensor type and select a functional replacement.
- After replacement, adjusted the sensor trigger height and carried out the balance calibration.
Cause
The engineers found that the imbalance sensor had failed as a result of improper operation, leaving the imbalance protection out of action; the original sensor type was unknown in this case.
What was done
The engineers fitted an SS49E Hall sensor, matched to the input stage by comparing signals with an oscilloscope, then adjusted the trigger height and re-ran the balance calibration. In this case the centrifuge was returned to working order.
Safety
The imbalance sensor is a safety device: before returning the centrifuge to use, confirm the protection actually responds, following the manufacturer's service documentation, and run a test spin with the lid closed, a properly balanced rotor and nobody standing over the machine.
Lesson: Mechanical abuse of a centrifuge often takes out the imbalance protection first, so after any such event the sensor, its magnet and the trigger height must be checked and recalibrated before the rotor is spun again.
Covered in the course: Lab Analyser Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.