Added functionality available only on the 568:

Easily trend and analyze data with included FlukeView® Forms software Quickly download stored data with USB connection See your data right away without leaving the site, using the USB and your laptop Extend your battery life by powering the digital thermometer from your laptop via the USB

Features and benefits of the 568 and 566:

Measure -40 °C to 800 °C /-40 °F to 1472 °F (568) or -40 °C to 650 °C/-40 °F to 1202 °F (566) Easily access advanced features with the soft-key buttons and dot-matrix display Measure smaller objects from further away, with a distance-to-spot ratio of 50:1 (568) or 30:1 (566) Compatibility with all standard miniconnector Type-K thermocouples allow you to preserve your thermocouple investments Confidently measure a wide variety of surfaces, with the adjustable emissivity feature, including a built-in material table Capture multiple points of data (up to 99 with the 568, and 20 with the 566), for downloading and recalling later Easily adapt to lighting conditions with 2 levels of backlight Audible and visual alarms instantly alert you to measurements outside of your set limits Quickly identify problems with the MIN, MAX, AVG, and DIF functions Make contact thermometer measurements right away with the included Type-K thermocouple bead probe Confidently troubleshoot equipment with 1 % measurement accuracy Versatile interface with 6 languages from which to choose