The uncomfortable truth about calibration is that it's a snapshot. Your balance was within tolerance on the day we calibrated it — but a knock, a spill, a moved bench or simple drift can change that any week of the year. The defence is a routine so simple it actually gets done.
The two-minute routine
Choose one or two check masses that bracket your typical working range — for an analytical balance weighing samples around 50 g, a 50 g mass alone does most of the work. At the start of each working day (or each shift, for critical work): confirm the balance is level, zero it, place the check mass, and record the reading with date and initials. That's it. The value of the routine isn't any single reading — it's the trend line those readings build.
Set action limits before you need them
Decide in advance what reading triggers action, and write it into the procedure. A common approach is a warning limit (investigate: cleanliness, level, draughts, static) and an action limit (stop using the balance for reportable work and call your calibration provider). Deriving limits from your tolerance and the balance's calibrated uncertainty keeps them defensible — we're happy to help you set them when we calibrate.
Look after the check masses
The routine is only as good as the mass on the pan. Handle check masses with tweezers or gloves — fingerprints genuinely add mass — store them covered, and have them calibrated periodically so their values are traceable to national standards maintained by the National Measurement Institute. They don't need to be the highest class of mass; they need to be stable, documented, and treated with respect.
Why auditors love this (and your intervals will too)
Under ISO/IEC 17025 and most quality frameworks, intermediate checks between calibrations are expected for equipment whose performance matters — it's one of the things NATA assessors look for in accredited laboratories. But the practical payoff is bigger than audit comfort: months of stable check records are the strongest evidence there is for keeping (or extending) your calibration interval, and a drifting trend catches a failing balance before it quietly invalidates weeks of results.
Between checks and calibration
In-house checks and accredited calibration aren't alternatives — they're partners. The check tells you something changed; the calibration tells you by exactly how much, against traceable references, with stated uncertainty. Run both and your weighing results become very hard to argue with.
Want a check procedure template and sensible action limits for your balances? Ask when you book your next calibration — we'll set it up with you.