Understanding proximity sensor IP ratings

The IP ratings established by the IEC are often misunderstood or misapplied, which can cause problems for the user and potentially be dangerous.

08/09/2012


The International Electrotechnical Commission (IEC) established a classification system to rate the degree to which the enclosures of electrical components are sealed against the intrusion of foreign bodies such as dust and moisture. This classification system implies various degrees of ingress protection, and is indicated by the letters “IP” followed by two digits. The first digit represents the degree of protection afforded against solid objects, while the second signifies the degree of protection provided from the ingress of water. 

Ingress protection ratings were established to create uniform performance requirements of electronic enclosures intended for specific environments. These guidelines describe in general how an electronic device will function in a particular environment. However, these ratings do not ensure how a device functions when outside variables are introduced.

Proximity sensors and other electronic sensing devices are typically rated between IP65 and IP69K. In this case, the “6” indicates that the equipment is dust-tight, while the second digit rates the amount of water ingress allowed as indicated below:

  • IP65: Protected from low-pressure jets from all directions for 1 min with limited ingress permitted
  • IP66: Protected from direct sprays from all directions for 1 min with limited ingress permitted
  • IP67: Protected from the effects of immersion from 15 cm to 1 m for 30 min without water ingress
  • IP68: Protected from complete continuous submersion in water without water ingress under conditions that are specified by the manufacturer
  • IP69K: Protection from hot steam jet cleaning per EN 60529 and DIN 40050-9. This provides protection from water pressure rated at 1,450 psi at a temperature of 176 F. The pressure is applied directly to the sensor in 30 deg angle increments (0, 30, 60, and 90 deg) for 30 sec at each point for a total of 2 min without water ingress.  

These ratings are often misunderstood and misapplied by the user. For example, many users assume that a rating of IP67 or IP68 allows a device to function while underwater for the time specified by the IP rating. This is not the case, as the rating only ensures that the device will function properly after it is removed from the water. 

Another misconception is that an ingress protection rating of IP69K automatically complies with IP67 and IP68. IP69K protects from pressure and jet spray, but the device may not be suitable in applications where it is immersed in water. Therefore, IP69K-rated devices are often used in washdown environments, such as those found in breweries, car washes, and food and beverage applications, but not in applications where the device is immersed in water. 

To be rated IP68, a device must meet the requirements of IP67. However, the company that produces the component determines what additional ingress protection the device contains for the IP68 rating. The manufacturer also determines if there are temperature constraints on these specifications, as temperature fluctuations are known to affect the capability of electrical devices to function properly. 

Learn more about proximity sensors and the diverse ways they can be used in the field following the link at the bottom of the file.

- Source: Turck USA. Edited by CFE Media: Control Engineering, Plant Engineering, Consulting-Specifying Engineer.