The IP rating found in electronic data sheets or specifications is designed to give reliable standards for determining the suitability of enclosures for conditions such as moisture, rain and dust.
Technically, IP stands for Ingress Protection or sometimes considered as Internal Protection and the ratings are defined by the international standard EN 60529 (British BS EN 60529:1992, European IEC 60509:1989).
The rating itself consists of numeric values. The first digit is a number 0-6 which indicates the size of the particles for which the enclosure is rated. A rating of 1 means it is only protected against solid objects over 50mm that includes the accidental touch by a hand, while a 6 means it is an enclosure that eliminates all dust.
The second digit ranges from 0-8 and describes the potential for intrusion by water including drips, sprays and submersion. For example, a number 4 means that splashing water from any side will not have a harmful effect on
mechanical or electrical components in the enclosure; and an 8 means that the enclosure can be continuously immersed in water over one meter in depth.
You will see many robust electrical enclosures typically have a rating of IP 67, which means that they can be considered as dust-free and can withstand submersion in water but for no longer than thirty minutes and not over one meter in depth. It is also possible to have different parts of the same enclosure with different ratings.
Full list of ratings
First Digit
0: No special protection
1: Protection from a large part of the body such as a hand (but no protection from deliberate access); from solid objects greater than 50mm in diameter.
2: Protection against fingers or other object not greater than 80mm in length and 12mm in diameter.
3: Protection from entry by tools, wires, etc., with a diameter of thickness greater than 1.0mm.
4: Protection from entry by solid objects with a diameter or thickness greater than 1.0mm
5: Protection from the amount of dust that would interfere with the operation of the equipment.
6: Dust tight.
Second Digit
0: No special protection
1: Protection from vertically dripping water.
2: Protection from vertically dripping water with <15° tilt
3: Protection from sprayed water.
4: Protection from splashed water.
5: Protection from water projected from a nozzle (∅=6.3, 12.5l/min)
6: Protection against heavy seas, or powerful jets of water (∅=12.5, 100l/min)
7: Protection against immersion (1m/30 min)
8: Protection against complete, continuous submersion in water (depth/time defined by a client)
9K: Protection against high pressure, high temperature (80°c) pressure washing
