As has been discussed previously, industrial sensors must be able to withstand some pretty punishing conditions. Although industrial sensors incorporate some of the same high-end technology found in, say, the blu-ray disc player in your home theater system, it’s not likely that your BD player is going to be subjected to punishing shock, vibration, and general abuse as do the sensors in your industrial machinery. To be sure, your blu-ray player doesn’t need to be protected against hydraulic fluid or moisture ingress. Which brings me to the topic of this entry: Ingress protection for industrial sensors.
In order to be viable in typical industrial environments, industrial sensors must often be able to tolerate getting wet, sometimes really, really wet. Fortunately, most sensors do indeed incorporate some degree of ingress protection by design. And it’s pretty easy to choose the proper sensor for a particular set of expected conditions thanks to a method of rating method outlined under international standard IEC 60529. This standard takes the somewhat vague term “waterproof” and provides specific details as to just how waterproof an electronic device is.
An IP (Ingress Protection) rating for an electronic device typically consists of the letters IP, followed by a two-digit number. The first digit identifies the protection against intrusion of solid objects (dirt, hand tools, your fingers, etc.):
|
Level |
Object size protected against |
Effective against |
|
0 |
— | No protection against contact and ingress of objects |
|
1 |
>50 mm | Any large surface of the body, such as the back of a hand, but no protection against deliberate contact with a body part |
|
2 |
>12.5 mm | Fingers or similar objects |
|
3 |
>2.5 mm | Tools, thick wires, etc. |
|
4 |
>1 mm | Most wires, screws, etc. |
|
5 |
Dust protected | Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment; complete protection against contact |
|
6 |
Dust tight | No ingress of dust; complete protection against contact |
Most industrial sensors are rated for intrusion protection to IP5_ or IP6_.
The second digit in the IP-rating, which is the one we’re most concerned with, identifies the level of protection again moisture ingress:
|
Level |
Protected against |
Testing for |
Details |
|
0 |
Not protected | — | — |
|
1 |
Dripping water | Dripping water (vertically falling drops) shall have no harmful effect. | Test duration: 10 minutesWater equivalent to 1mm rainfall per minute |
|
2 |
Dripping water when tilted up to 15° | Vertically dripping water shall have no harmful effect when the enclosure is tilted at an angle up to 15° from its normal position. | Test duration: 10 minutesWater equivalent to 3mm rainfall per minute |
|
3 |
Spraying water | Water falling as a spray at any angle up to 60° from the vertical shall have no harmful effect. | Test duration: 5 minutesWater volume: 0.7 litres per minute Pressure: 80–100 kN/m² |
|
4 |
Splashing water | Water splashing against the enclosure from any direction shall have no harmful effect. | Test duration: 5 minutesWater volume: 10 litres per minute Pressure: 80–100 kN/m² |
|
5 |
Water jets | Water projected by a nozzle (6.3mm) against enclosure from any direction shall have no harmful effects. | Test duration: at least 3 minutesWater volume: 12.5 litres per minute Pressure: 30 kN/m² at distance of 3m |
|
6 |
Powerful water jets | Water projected in powerful jets (12.5mm nozzle) against the enclosure from any direction shall have no harmful effects. | Test duration: at least 3 minutesWater volume: 100 litres per minute Pressure: 100 kN/m² at distance of 3m |
|
7 |
Immersion up to 1 m | Ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 m of submersion). | Test duration: 30 minutesImmersion at depth of 1m |
|
8 |
Immersion beyond 1 m | The equipment is suitable for continuous immersion in water under conditions which shall be specified by the manufacturer. Normally, this will mean that the equipment is hermetically sealed. However, with certain types of equipment, it can mean that water can enter but only in such a manner that it produces no harmful effects. | Test duration: continuous immersion in waterDepth specified by manufacturer |
While an IP65 rating is fairly common, the trend is towards sensors with a more substantial IP67 or IP68 rating.
While the IP67 rating is fairly straightforward, the IP68 rating seems to cause a lot of confusion. The reason for this is that the IP68 rating is subject to conditions specified by the manufacturer. For equipment to be rated to IP68, it must be suitable for continuous immersion underwater at a depth specified by the manufacturer. Essentially, IP68 can be taken to mean that the equipment is protected at least as well as IP67, but how much better must be specified by the manufacturer of the equipment.
Another IP rating of interest is the IP69K rating. The IP69K rating, detailed in German DIN standard 40050-9, provides specific requirements (water temperature, pressure, flow rate, etc.) for equipment designed to withstand high-pressure, high-temperature washdown.
Some examples of IP69K-rated sensors include transducers and inductive sensors.
Additional information on Ingress Protection standards can be found here.
