What are IP Ratings

In the wonderful world of engineering standards, BS EN 60529:1992 is probably one of the most used in electronic and electrical engineering. Any time an electrical product is sold within some sort of enclosure, it will have an IP rating associated with it. The standard defines what environments the enclosure can protect the electronics inside it from. IP comes from the french term Indice de Protection which translates to the Protection Factor. Basically, the higher the numbers, the more protection it can afford against dust and liquid.

An IP rating consists of the letters "IP" followed by two single digits. Using IPXY, X denotes protection from solid particles, like dust or fingers; and Y denotes protection from liquids, water being the most common test. The enclosure must be able to operate normally whilst being subjected to the rated (in the tables below) for no more than 30 minutes.

X	Description
0	No protection
1	Protection against objects larger than 5cm
2	Protection against objects larger than 1.25cm (e.g fingers)
3	Protection against objects larger than 1.25cm (e.g wires/screwdrivers)
4	Protection against objects larger than 1mm (e.g insects)
5	Protection against dust
6	Dust tight

Y	Description
0	No protection
1	Dripping water
2	Dripping water at an angle
3	Falling water
4	Water splashes
5	Water jet
6	Powerful water jet
7	Immersion < 1m
8	Immersion > 1m
9	High pressure, high temperature water jet

These ratings have been seen recently in the latest Apple and Samsung smartphones. The IPhone 7 claims IP67, so dust tight, and waterproof to less than 1m. Samsungs S8 is rated at a high IP68, so it is dust tight and waterproof over 1m. Equally, if you have a device that like a mains plug, it has big holes in it where it fits into the other plug. These holes won't stop dust, and definitely don't stop water in any form, but it will stop you putting your fingers inside it. These sort of devices are rated as IP2X, with the X meaning it could be any form of waterproof, but it is untested.

It is important to note that sometimes a device can have a dual rating. Due to the way that the liquid protection scale works, you could in theory have a device that can withstand immersion more than 1m (IPX8), but fails to stop water jets. So sometimes you will get manufacturers specifying that is can withstand one or the other to stop confusion.

The ratings for water immersion are also very vague, when underwater, pressures can change and increase massively depending on the movements of the device. If it is a watch, it can be put under huge pressures if the user starts swimming with it. Even if it is rated to immersion <1m, that movement could put the device at a much higher pressure, as if it is much deeper underwater. This is why some devices like smart watches are IP67 rated, but call themselves "splash resistant" rather than water resistant.