What does instrument IP rating mean?

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 you vital information? Actually, the IP rating lets you know whether a piece of test equipment is suited for your application and test environment.


Key Concepts
  • IP rating is the degree to which an instrument can withstand invasion by foreign matter.

  • The first digit refers to the degree to which solid objects can penetrate the enclosure.

  • The second digit refers to the degree to which moisture affects the instrument.

IP rating nomenclature
So what?
Saving face
More Info:

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 you vital information? Actually, the IP rating lets you know whether a piece of test equipment is suited for your application and test environment.

IP stands for ingress protection , which is the degree to which an instrument can withstand invasion by foreign matter. The International Electrotechnical Commission (IEC) established the IP rating system in its Standard 529; it is used as a guide to help you protect the life of an instrument. Also, it helps you make a more informed instrument purchase decision by ensuring that a piece of test equipment is designed to work in its intended environment. The IP rating should appear in all product literature. Question the quality of the instrument if the literature does not show an IP rating.

IP rating nomenclature

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, the better the degree of protection. What would a typical rating of IP54 indicate about the application capabilities of a model (Fig. 1)? 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 (See "Protection against access to hazardous parts" and "Protection against ingress of solid foreign objects"). A level of 5 indicates dust protected , as well as protected from invasion with a wire or other object down to 1.0 mm. There is only one higher category — dust tight .

The second digit refers to moisture (See "Protection against ingress of liquids"). A rating of 4 means resistance to splashing water, any direction. The higher ratings of 5%%MDASSML%%8 indicate levels of jetting water and immersion. Not too many electricians or technicians need to work under water!

So what?

Suppose an instrument under consideration was rated to only IP43. What would that tell you about its usability? Could it be thoroughly used in a quarry or cement plant? Hardly! The particulate rating 4 indicates objects equal to or greater than 1 mm — a boulder in comparison to particles typically produced by industrial processes. Flying dust could put the unit out of commission before the purchasing agent has authorized the bill payment.

What about a paper mill or other industrial processing plants? Wrong application again! The moisture rating 3 covers spraying water, up to a 60-deg 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 an instrument is rated at IP42. A moisture rating of 2 indicates dripping water. Therefore, it would not be resistant to flying spray. Buying an instrument for an environment that exceeds its IP capabilities means that you will probably need another one 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 industrial manufacturing plants.

Saving face

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 environments in which the instrument will probably be used, the nature of foreign materials to be encountered, and what that will demand in terms of IP rating. Then purchase an instrument that matches or exceeds that requirement.

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 provides objective meaning.

More Info:

Questions about instrument IP ratings can be directed to Jeff Jowett at 610-676-8539, jeff.jowett@megger.com , or visit megger.com . Article edited by Jack Smith, Senior Editor, 630-288-8783, jsmith@reedbusiness.com .

Protection against access to hazardous parts (first digit)

Number Description
0Not protected
1Protected against access with back of hand (50 mm)
2Protected against access with jointed finger (12 x 80 mm)
3Protected against access with a tool (2.5 mm)
4, 5, 6Protected against access with a wire (1.0 mm)

Protection against ingress of solid foreign objects (first digit)

Number Description
0Not protected
1Objects equal or greater than 50 mm
2Objects equal or greater than 12.5 mm
3Objects equal or greater than 2.5 mm
4Objects equal or greater than 1 mm
5Dust protected
6Dust tight

Protection against ingress of liquids (second digit)

Number Description
0Not protected
1Water dripping vertically
2Water dripping, enclosure tilted to 15 deg
3Spraying water, to 60 deg angle from vertical
4Splashing water, any direction
5Jetting water, any direction
6Powerful jetting water, any direction
7Temporary immersion in water
8Continuous immersion in water

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