Helena AC 4: sampling probe misses tubes and dispenses to wrong positions after downtime
What happened
After the analyzer sat idle, the sampling arm lost track of coordinates: it moved to the wrong positions, failed to dip into sample tubes, and started dispensing into cuvettes.
What was checked
- Repeated the axis coordinate setup — the mispositioning persisted, so the fault was not purely calibration.
- Checked needle patency with an aspiration test; during the draw the syringe pump reported an error, pointing at the probe assembly.
- Concluded that the worn probe was disturbing the sensitive liquid level detection the analyzer relies on for positioning.
Cause
In this case the engineers found a worn, faulty sampling probe: its condition degraded the liquid level sensor signal, and the analyzer, relying on that signal, behaved as if its coordinates were lost after the idle period.
What was done
Replaced the sampling probe (a serviceable second-hand unit) and repeated the axis coordinate setup; the analyzer then positioned and sampled normally. The fix depends on a standard coordinate setup procedure from the manufacturer's service documentation, done by authorised personnel. In this reported case the fault was solved.
Safety
The probe and fluid path carry patient material — treat them as biohazardous, wear gloves, disinfect after the work — and run the electrical safety test before returning the analyzer to use.
Lesson: On analyzers that confirm position by liquid level, a worn or contaminated sampling needle can look exactly like a coordinate fault — check the probe hardware before re-teaching the axes.
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.