Thermometer calibration for HACCP: what a "calibrated sensor" means and when you need a certificate

Thermometer calibration in a food business, in short: every sensor needs a demonstrable comparison against a reference standard. Since 2023 the metrology inspectorate has been running targeted checks of calibration documents in chilled and frozen storage — which is why every sensor we supply comes with a calibration certificate from an accredited laboratory, included; it is renewed with regular sensor exchanges, typically every 2 years. An uncalibrated thermometer can meanwhile read two degrees off — which is worse than none, because it gives you false peace of mind.

What calibration is

Calibration compares your sensor against a reference standard at known temperatures (e.g. −18 / 0 / +5 °C). The result is a set of measured deviations — either confirmation the sensor reads correctly, or corrections to apply. Without calibration you don't know whether your "4 °C in the fridge" isn't actually 6.

What metrological traceability is

The key word during an inspection. It means the chain of comparisons leads all the way to a national standard: your sensor was compared against a reference that was calibrated in an accredited laboratory. Such a calibration is demonstrable — and that's precisely what an inspector cares about.

Do HACCP thermometers need official verification?

No. Ordinary thermometers and sensors in a food-service operation (fridges, freezers, storage, hot holding) are not subject to statutory metrological verification — the law reserves that for specific regulated instruments. HACCP does, however, require the accuracy of your instruments to be demonstrable, and that is exactly what regular calibration with metrological traceability provides.

When a calibration report is enough and when you need an accredited certificate

• Regular operations (shop, restaurant, butcher): a calibration report with traceability to an accredited standard is sufficient in practice — what matters is that deviations are documented and measurements defensible.
• Demanding audits (IFS/BRC production plants, pharma, large buyers): the auditor may require a certificate issued directly by an accredited laboratory for every sensor. With us it comes with every sensor, included in the price.

How often to calibrate

The common recommendation for food businesses is recalibration every 2 years — and always after suspected damage (a dropped sensor, extreme temperature, nonsensical readings). Keep the calibration date and validity documented; inspections ask for them.

What our calibration report looks like

A calibration report is not a rubber stamp — it's the document you put on the table during an inspection. Ours includes, for every sensor:

• Report number and sensor identifier — the document pairs unambiguously with a specific monitoring point on site.
• Calibration points at −18 / 0 / +5 °C — the temperatures a freezer and fridge actually operate at, not a laboratory abstraction.
• Measured deviations and corrections at each point — in black and white, how far off the sensor read and what correction applies.
• Details of the reference standard used, including the number of its accredited calibration certificate and its measurement uncertainty.
• An acceptance criterion of ±0.5 °C — a sensor outside it is retired or deployed only with a documented correction.
• The recommended recalibration date — calibration validity readable at a glance.

Metrological traceability is closed end to end: the reference standard we calibrate against is itself calibrated in an accredited laboratory to ISO/IEC 17025, so the chain of comparisons leads all the way to a national standard. And the corrections don't stay on paper — the system applies them automatically to every single reading, so charts and HACCP records show the true temperature.

How TempeStorm handles it

Every sensor we ship comes calibrated — multi-point, traceable to an accredited reference standard, with a calibration report; the measured corrections are applied automatically, so charts and HACCP records show the true temperature. We track calibration validity for you. A calibration certificate from an accredited laboratory is included with every sensor we supply — including regular sensor exchanges.