The incubator display is not the measurement

Every lab has one incubator that never alarms. It shows the right temperature and the right gas, day after day, and nobody worries about it.

That is the one to check most carefully.

What the screen is really telling you

An incubator's display reports what its own sensor believes. The sensor sits in one place, it ages, and it is calibrated against itself. If it drifts, the display drifts with it, and the screen keeps showing exactly the value you set.

So a perfect display proves only that the incubator agrees with itself. It does not prove the chamber matches the setting.

The things that move a chamber away from its setting are ordinary:

• a sensor slowly ageing
• a gas cylinder change, or a regulator that has been knocked
• a door seal that has worn, or a door opened more often on busy days
• humidity changing after the water pan is refilled
• the unit being moved, serviced or restarted

None of these sets off an alarm on the day it starts.

Two readings, not one

The habit that catches drift is simple: measure the chamber with an independent instrument on a fixed schedule, and write down both numbers, what the display says and what your own analyser or thermometer says.

Then watch the gap between them, not the display.

• A gap that stays small and steady means the unit and your instrument agree.
• A gap that grows slowly is the early warning. It usually appears weeks before anything you would notice in the lab.
• A sudden jump points to an event: a cylinder change, a service, a moved probe. The log tells you which.

The value of this is in the record over time. A single reading tells you very little. The same reading taken the same way every day tells you when something changed.

Making the habit stick

A check only helps if it happens on the dull days too. A few things make that easier:

• Same time, same way. Measure at a fixed point in the day, after the unit has been closed for the same length of time, with the same instrument.
• Write it down at once. A reading recorded later from memory is not a record.
• Record what you did about it. When the gap moves, note what you checked, what you changed and who did it. The reading stays as it was; your response sits beside it.
• Look at the trend weekly. Five minutes with the last few weeks of readings shows more than any single day.

Why this matters beyond the incubator

The same idea applies across the lab. Gas, pH, temperature and storage levels all have a display that can be wrong and a measurement that can be checked. In each case the protection is the same: an independent reading, written down every time, and a look at how it changes.

Quality is what the record can show, not what anyone remembers.

Try it free

Our free Daily QC tool records the display and your own reading side by side for every unit, dates each entry on our server so nothing can be back-dated, and shows the gap as a trend. A gap that grows raises a calibration flag on that unit.

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