It is the rating standards for an instrument’s capability to protect its electronic components from corrosion by water or dust. It is common for electronic thermometers to be splashproof or waterproof and the International Electrotechnical Commission (IEC) rating system classifies the degrees of protection provided. The International Protection Rating code (or IP code) consists of the letters “IP” followed by two numbers. The first number tells you how protected an instrument’s electronics are from penetration by solids (like dust) and the second number tells you how they stand up against liquids according to the following table: First Number 0no protection 1Protected against solids objects over 50mm (eg. Accidental touch by hands) 2Protected against solids objects over 12mm (eg. Fingers) 3Protected against solids objects over 2.5mm (eg. Tools and wires) 4Protected against solids objects over 1mm (eg. Tools, wires and small wires) 5Protected against dust – limited ingress (no harmful deposit) 6Totally protected against dust   Second Number 0no protection 1Protected against vertically falling drops of water 2Protected against direct sprays up to 15° from the vertical 3Protected against direct sprays up to 60° from the vertical 4Protected against sprays from all directions – limited ingress permitted 5Protected against low pressure jets of water from all directions – limited ingress permitted 6Protected against strong jets of water eg. For use on shipdecks – limited ingress permitted 7Protected against the effects of temporary immersion between 15cm and 1m. Duration of test 30 minutes 8Protected against long periods of immersion under pressure   If, for example, a thermometer had a rating of “IP65”, that would mean that it was tested and found completely protected against dust as well as protected against low pressure jets of liquid from all sides, but NOT protected against immersion, or an accidental drop into the soup!