Veriteq Instruments is the leader in mission-critical temperature and humidity monitoring solutions. Withnell Sensors is the UK and Ireland distributor for Veriteq products.
An introduction to thermocouples at Wikipedia, covering theory and practical applications, plus links to other resources.
"An electronic device that records data over time or in relation to location either with a built in instrument or sensor or via external instruments and sensors." Read more about data loggers in this article at Wikipedia.