Sensor Environmental Ratings

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While one cannot guarantee (at selection time) that a sensor will perform properly, it is possible to select a sensor that will almost certainly fail in a stamping environment.   This happens when you select a sensor with an insufficient environmental rating.   The important specification goes by several names including:

• Enclosure Rating (or simply "Enclosure")
• Degree of Protection (or simply "Protection")
• Environmental Rating
• Protection Rating

The specification will refer to either an IP or NEMA rating (or both).   Let's go over the IP rating first.

IP Ratings
The IP (Ingress Protection) rating system was published by the International Electrotechnical Commission (IEC) to classify the degree of protection provided by the enclosures of electrical devices.   It consists of a two-digit rating system where a higher number indicates a better degree of protection.   The first digit can run from 0-6, and indicates the degree of protection against solid foreign objects such as fingers, dirt, and dust.   The first digit ratings are summarized below:

1st Digit IP Rating	Protection Summary
0	No protection
1	Objects larger than 50 mm cannot enter the device
2	Objects larger than 12.5 mm cannot enter the device
3	Objects larger than 2.5 mm cannot enter the device
4	Objects larger than 1 mm cannot enter the device
5	No harmful ingress of dust
6	Dust tight - No ingress of dust whatsoever

The second digit can range from 0-8, and indicates the degree of protection against harmful ingress of water.   The 2nd digit ratings are summarized below:

2nd Digit IP Rating	Protection Summary
0	No protection
1	Dripping water (vertically)
2	Water dripping from up to a 15° angle
3	Water splashed at up to a 60° angle
4	Water splashed from any angle
5	Water Jet - 6.3 mm nozzle, 12.5 Liters/Minute
6	Water Jet - 12.5 mm nozzle, 100 Liters/Minute
7	Immersion up to 1 m
8	Immersion to a specified depth beyond 1 m

Ideally, any sensor for in-die use should have an IP-67 rating.   An IP-67 rated sensor is dust tight, and protected against immersion in water to a depth not exceeding 1 meter.   An IP-68 rated sensor is unnecessary because it is unlikely that you will run your dies while they're submerged to a depth exceeding one meter.

Theoretically, a sensor with an IP-66 rating should be able to stand up to a stamping environment, however the water jet test used to verify the rating has a short (3 minute) duration.   The longer exposure time to lubricant in a stamping application can often lead to ingress, which can cause premature sensor failure.

NEMA Ratings
NEMA, The National Electrical Manufacturers Association, has a series of environmental ratings for enclosures.   The NEMA ratings are more comprehensive than the IP ratings; often specifying factors like corrosion resistance, gasket performance, and construction details that are not covered by the IP ratings.   Therefore it is possible to equate some NEMA ratings to IP ratings, but not vice-versa.   The table below shows some NEMA ratings and their corresponding IP ratings.

NEMA Rating	Equivalent IP Rating
3	IP-54
4, 4X	IP-66
6	IP-67
6P	IP-68

In the absence of an IP rating, any device for in-die use should have a NEMA 6 or NEMA 6P rating.