Atemperature data logger, also calledtemperature monitor, is a portablemeasurement instrument that is capable of autonomously recordingtemperature over a defined period of time. The digital data can be retrieved, viewed and evaluated after it has been recorded. Adata logger is commonly used to monitor shipments in acold chain and to gather temperature data from diverse field conditions.
A variety of constructions are available. Most have an internalthermistor orthermocouple 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 fromGPS devices.
Depending on the use, governingquality management systems sometimes requirecalibration to national standards and compliance with formalverification and validation protocols[1]
Choices of temperature data loggers can be based on many factors, such as:
Autonomous data loggers can be taken to diverse locations that cannot easily support fixed temperature monitoring equipment.[3] These might include: mountains, deserts, jungles, mines, ice flows, caves, etc. Portable data loggers are also used in industry and laboratory situations where stand-alone recording is desired.
Temperature sensitive products such as foods,[4] pharmaceuticals,[5] and some chemicals are often monitored during shipment and logistics operations. Exposure to temperatures outside of an acceptable range, for a critical time period, can degrade the product or shorten shelf life. Regulations and contracts make temperature monitoring mandatory for some products.
Battery-powered, formerly mechanical, the data logger is today an electronic device that can be programmed to record individual values over periods of a few hours to several months. Most are used to monitor temperature conditions, and some versions can also measure the relative humidity.
Data loggers are often small enough to be placed inside aninsulated shipping container or directly attached to a product inside arefrigerator truck or arefrigerated container. These monitor the temperature of the product being shipped. Some data loggers are placed on the outside of the package or in the truck orintermodal container to monitor the air temperature. Placement of data loggers and sensors is critical: Studies have shown that temperatures inside a truck or intermodal container are strongly affected by proximity to exterior walls and roof and to locations on the lading.[6][7]
Modern digital data loggers are very portable and record the actual times and temperatures. This information can be used to model product degradation and to pinpoint the location and cause of excessive exposure.
The measured data reveals whether the goods in transit have been subjected to potentially damaging temperature extremes or an excessiveMean kinetic temperature. Based on this data, the options may be:
Multiple replicate shipments of data loggers are also used to compare modes of shipment (routes, vendors) and to develop composite data to be used inpackage testing protocols.[9]
There are many brands and models of data loggers. Most are a connectable device that must be plugged into a computer to extract the data that the logger has logged.
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