By Jeff Jowett; Senior Application Engineer, Megger

Somewhere in the fine print of most test equipment product bulletins, you’ll find an IP rating. Is this just “boilerplate” or does it give the buyer vital information? In fact, the IP rating lets the buyer know whether a piece of test equipment is suited for his/her application and test environment.

“IP” stands for “ingress protection”, that is the degree to which the instrument can withstand invasion by foreign matter. The IP rating system has been established by the IEC (International Electrotechnical Commission), in their Standard 529, and is used as a guide to help the end user protect the life of the instrument. It also can help the end user make a more informed purchase decision by ensuring that the piece of test equipment is designed to work in the environment(s) that he/she faces. The IP rating should appear in all product literature. Question the quality of the piece of equipment if the literature does not show an IP rating.

The IP rating is comprised of two digits, each signifying a separate characteristic. The designation indicates how well the item is sealed against invasion by foreign matter, both moisture and dust (the higher the number(s), the better the degree of protection). What would a typical rating of IP54 tell a buyer about the application capabilities of a model? If you want to sound thoroughly knowledgeable, that’s IP five-four, not fifty-four. Each digit relates to a separate rating, not to each other.

The first digit refers to particulate ingress, reflecting the degree to which solid objects can penetrate the enclosure. A level of “5” indicates “dust protected”, as well as protected from invasion with a wire down to 1.0 mm. There is only one higher category: “dust tight”. The second digit refers to moisture. A rating of “4” means resistance to “splashing water, any direction.” The higher ratings of 5 through 8 indicate “jetting water” and “temporary” or “continuous” immersion. Not too many electricians need to work under water!

So what? Well, suppose an instrument under consideration was rated only to IP43. What would that tell you about its usability? Could it be thoroughly utilized in a quarry or cement plant? Hardly! The particulate rating 4 indicates “objects equal or greater than 1 mm”. That’s a boulder in comparison to particles typically produced by industrial processes. Flying dust could put the unit out of commission before the purchasing agent is done stalling payment. What about a paper mill or other industrial processing plants? Wrong application again! The moisture rating 3 covers “spraying water, up to 60 °-angle from vertical.” This is adequate protection for occasional incidental encounters, but still leaves a wide margin for invasion where water is a common hazard. Moisture could penetrate the unit, corrode and short out the board, and produce nagging repair delays that could critically disrupt a time-focused preventive maintenance program.

Suppose the unit is rated at IP42. A moisture rating of 2 indicates dripping water. Therefore, it would not be resistant to flying spray. Acquiring an instrument for an environment that exceeds its IP capabilities likely means that you’ll need another very soon. What about a rating of IP40? A moisture rating of 0 means that the unit is not protected against any liquid ingress. Where would you use an instrument like this? It obviously is not designed for use in the field.

Avoid the embarrassment of having to tell the “boss” or purchasing agent that a unit has failed when they still think of it as “brand new”. Make a mental review of the types of environment in which the instrument will possibly be used, the nature of foreign materials to be encountered, and what that will demand in terms of IP rating. Then purchase a unit that matches or exceeds that requirement, and don’t be caught red-faced with a “brand new” instrument that is literally “choked with dust” or “dead in the water”. Any advertising blurb can call a unit “water resistant” or the like, but the IP rating actually gives objective meaning.

 

Protection against Access to Hazardous Parts (First Digit)

Number	Description
0	Non-protected
1	Protected against access with back of hand (50 mm)
2	Protected against access with jointed finger (12 x 80 mm)
3	Protected against access with a tool (2.5 mm)
4, 5, 6	Protected against access with a wire (1.0 mm)

 

Protection against Ingress of Solid Foreign Objects (First Digit)

Number	Description
0	Non-protected
1	Objects equal or greater than 50mm
2	Objects equal or greater than 12.5mm
3	Objects equal or greater than 2.5mm
4	Objects equal or greater than 1mm
5	Dust protected
6	Dust tight

 

Protection against Ingress of Liquids (Second Digit)

Number	Description
0	Non-protected
1	Water dripping vertically
2	Water dripping, enclosure tilted up to 15°
3	Spraying water, up to 60° angle from vertical
4	Splashing water, any direction
5	Jetting water, any direction
6	Powerful jetting water, any direction
7	Temporary immersion in water
8	Continuous immersion in water