A temperature data logger, also called temperature monitor, is a portable measurement instrument that is capable of autonomously recording temperature over a defined period of time. The digital data can be retrieved, viewed and evaluated after it has been recorded. A data logger is commonly used to monitor shipments in a cold chain and to gather temperature data from diverse field conditions.
A variety of constructions are available. Most have an internal thermistor or thermocouple or can be connected to external sources. Sampling and measurement are periodically taken and digitally stored. Some have a built in display of data or out-of-tolerance warnings. Data retrieval can be by cable, RFID, wireless systems, etc. They generally are small, battery powered, portable, and equipped with a microprocessor, internal memory for data storage, and sensors. Some data loggers interface with personal computers or smart phones for set-up, control, and analysis.
Some include other sensors such as relative humidity, wind, light, etc. Others may record input from GPS devices.
Depending on the use, governing quality management systems sometimes require calibration to national standards and compliance with formal verification and validation protocols
Choices of temperature data loggers can be based on many factors, such as:
Cost
Reusability
Battery life
Ease of use; set-up, readability, download data, analysis, etc.
Temperature range
Number of measurements stored
Accuracy and precision - degree of agreement of recorded temperature with actual
Resolution
Response time – the time required to measure 63.2% of the total difference between its initial and final temperature when subjected to a step function change in temperature; other points such as 90% are also used.
shock and vibration resistance
Water resistance – humidity, condensation, etc.
Size, weight, mounting
Certifications, calibrations, etc.
Software
Data export
Data integration with other systems
Autonomous data loggers can be taken to diverse locations that cannot easily support fixed temperature monitoring equipment.