BioSystems A25: unstable results and drifting baseline
What happened
A biochemistry analyzer gave unstable results across many parameters: controls jumped from run to run, and a baseline error appeared from time to time.
What was checked
- First ruled out the aspiration pump on the wash station.
- Reviewed the cuvette routine — as reported in the case, the plastic cuvettes were washed daily and replaced monthly — and checked cuvette cleanliness optically.
- Checked dispensing repeatability (five runs on glucose, as reported), plus the needle bore, syringe and heater.
- Inspected the lamp and the engineers found the filament visibly worn and deformed.
Cause
In this case the worn lamp filament was taken as the probable cause of the instability; fluidics and cuvettes could not be fully excluded, so the conclusion remains probable.
The cause is probable and was not fully confirmed.
What was done
The lamp was replaced and the analyzer was kept under observation; since the outcome is only probable, the engineers watch the controls and baseline over further runs before closing the case.
Safety
Isolate the analyzer from the mains and let the lamp cool completely before touching it — an old bulb is hot and fragile, and its glass should not be handled with bare fingers.
Lesson: When results drift across many parameters at once, check the optical source early — a tired lamp can imitate fluidics and cuvette problems.
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.