Using a solid-state peltier heat-pump, the Mini Calibration Bath quickly cools to about 36°F below ambient (near 32°F) and heats to approximately 130°F. Immerse your thermometer and compare its reading to a traceable reference thermometer. Operation is easy. One button for Hot, one for Cold. Fill its reservoir with crushed ice and a little water, turn the Cold button on, and in a few moments you'll have an ice-bath ready for calibrations at a perfect 32.0°F (±0.06°F). Our tests show the bath will maintain the ice point at 32.0°F with a stability of at least ±0.3°F for over four hours. For hot temperatures, the bath will continue heating until it reaches approximately 130°F. A thermostat will hold the bath near that temperature to prevent over-heating. The bath is powered by an included AC adaptor. It comes with a manual giving basic instructions for comparison calibration using the bath and a reference. Use a reference thermometer as shown or check our website for other affordable reference thermometers.