Cold-chain conditions must be monitored and documented, not only maintained. A temperature data logger records measurements at configured intervals and stores a time-stamped history that can be reviewed after storage or transport. This guide explains the main logger types and the criteria that matter for medical refrigerators, freezers, transport containers and other temperature-controlled applications.

What is a temperature data logger?

A data logger combines a temperature sensor, memory, a clock and a way to retrieve records. Depending on the model, the report may be downloaded through USB, transferred by Bluetooth or Wi-Fi, or viewed in a cloud service. Unlike a display thermometer, a logger preserves the sequence of measurements and makes short excursions easier to investigate.

Why documented monitoring matters

Vaccines, medicines, reagents and biological samples may have defined storage or transport limits. A logger helps the responsible team verify the recorded conditions, identify excursions, review equipment performance and prepare evidence for internal procedures or audits. The acceptable range, alarm limits, recording interval and required retention period must be set by the organisation's approved procedure and the requirements applicable to the stored material.

Common types of temperature loggers

  • Reusable USB loggers are suitable for repeated monitoring when reports are downloaded locally.
  • Single-use transport loggers accompany an individual shipment and provide a trip record.
  • Loggers with an external probe allow the sensor to remain inside a chamber or container while the display or body stays outside.
  • Wireless loggers use Bluetooth, Wi-Fi or a mobile connection for remote access and notifications, subject to network availability.
  • Temperature and humidity loggers monitor both parameters where relative humidity is relevant.

Current reusable solutions are listed in the temperature data logger category. For transport applications, also review medical insulated containers and transport cases.

Independent logger or built-in refrigerator controller?

The instruments serve different purposes. A refrigerator controller regulates the equipment and may provide its own alarms or records. An independent logger provides a separate measurement history and can be positioned according to a monitoring plan. In critical applications, the required arrangement should be defined during commissioning, qualification or the organisation's risk assessment.

How to choose a logger

  • Measurement range: it must cover the operating range and any expected excursion without saturating the sensor.
  • Accuracy and resolution: compare the specified performance in the part of the range that will actually be used.
  • Probe configuration: choose an internal sensor or an external probe according to the chamber, container and access requirements.
  • Memory and interval: calculate whether the capacity is sufficient for the monitoring period at the selected recording interval.
  • Reports and interfaces: check whether PDF, CSV, USB or remote access matches the organisation's workflow.
  • Alarms: determine whether local indication, email or other remote notification is required.
  • Power and environmental protection: consider battery life, enclosure rating and the conditions during storage or transport.
  • Calibration documentation: confirm the calibration route, traceability and recalibration interval required by the applicable procedure.

Choosing for refrigerators, freezers and transport

For a refrigerator, the measurement point and interval should reflect the monitoring plan rather than simply the coldest visible location. For low-temperature and ultra-low-temperature freezers, verify the logger and probe range before use. During transport, consider route duration, expected ambient conditions, report retrieval and whether real-time notification is necessary. A logger records conditions but does not replace a suitable refrigerator, freezer or qualified transport container.

Need help selecting a data logger?

Send us the required temperature range, application, monitoring duration, reporting format and alarm requirements. We will compare the available models and prepare a technically appropriate configuration. Contact Oselya.