A thermometer shows the temperature at that moment and supports the acceptance decision; a logger measures at intervals and shows afterwards when an excursion happened. The logger writes through the shipment, the thermometer decides at handover.

An infrared thermometer reads the surface only: a carton that stood in the sun can be warm outside and still cold inside. For an acceptance or rejection decision the product core is measured with a probe thermometer.

The logger's recording interval follows the length of the trip and how quickly an excursion affects the product; too long an interval misses a brief excursion.

  • The sensor goes inside the product or at the container's weakest point
  • It does not go beside the coolant, at the door opening or in front of the airflow

For equipment carrying frozen food, ATP requires a recorder that complies with EN 12830 and is verified to EN 13486; the records are kept for at least one year.