The Fluke 721-3650 is the most advanced and accurate temperature calibrator on the market. It features a wide temperature range of -45°C to 1200°C, and it can measure and source temperature with an accuracy of ±0.025°C. The 721-3650 also has a built-in reference thermometer, which eliminates the need for a separate reference probe. This makes it the ideal choice for calibrating temperature sensors and transmitters in the field or in the lab.