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Definitions, Specifications, and Primers

Rugged computing terminology and standards
(by Conrad H. Blickenstorfer)

What's an IP rating? Ingress Protection? How is that measured, and what does it mean? What does "intrinsically safe" mean? How do they do drop tests and such? Where can you find information on testing procedures? What are NEMA ratings? What does RoHS mean, and is it important? (Yes, especially if you deal with European markets). And what's FIPS 201? Or does a client request adherence to IEC 60601? Or what does a vendor need to do to comply with MIL-L-85762A for night vision imaging systems?

All of these terms, and more, you'll encounter in ths specifications and sales pitches of rugged computing equipment. Knowledge of what it all means is crucial to understanding the potential suitability of equipment for your applications, and also when discussing your needs with a vendor.

In this section you'll find explanations of the many definitions and terms used in rugged computing, and also information on the various rating systems employed to indicate ruggedness, sealing and other environmental protection. You'll also find descriptions and updates on enabling technologies, such as outdoor-readable notebook computers screens.

You also find primers of a variety of ancillary technologies, such as RFID, bar code scanning, and others. What you see now is just the beginning. Over time we'll be adding additional definitions, primers, and white papers.

Vendors: If you have Technology White Papers which you'd like to share with potential clients, please email us at

At we consider the Ingress Protection rating to be especially important. It is in the IEC (International Electrotechnical Commission) 60529 international standard and classifies how well electrical enclosures are protected against intrusion of solid objects, dust, and water. When used to indicate sealing of rugged computers, the IP rating tells you whether dust or water can get into your computer. Below is the IP rating table.

IP (Ingress Protection) Rating Table

SOLIDS (1st number) LIQUIDS (2nd number)
0 No protection 0 No protection
1 Protected against objects > 50mm (hands) 1 Protection against dripping water or condensation
2 Protected against objects > 12mm (fingers) 2 Protection against water spray 15 degree from vertical
3 Protected against objects > 2.5mm (tools/wires) 3 Protection against water spray 60 degree from vertical
4 Protected against objects > 1mm (small tools) 4 Protection against water spray from all directions
5 Protected against dust, limited ingress 5 Protection against low pressure jets of water
6 Totally protected against dust 6 Protected against heavy seas
7 N/A 7 Protection against the effects of immersion (6 inches to 3.3 feet)
8 N/A 8 Protected against continuous immersion (but under conditions defined by the manufacturer)

What is the MIL-STD-810F

It is an equipment testing standard by the United States Department of defense. It describes in detail testing procedures designed to determine how equipment holds up under a variety of conditions the equipment may encounter while being used, transported and stored. These conditions include temperature, impact, vibration, humidity, and more. Note that while the standard is extensively used for testing of rugged computing equipment, it was not specifically designed for that type of equipment. As a result, some tests are ambiguous when applied to computing equipment.

What is the difference between MIL-STD-810F and MIL-STD-810G?

MIL-STD-810F was introduced on January 1, 2000. MIL-STD-810G was introduced October 31, 2008, and supersedes MIL-STD-810F. The two documents are not substantially different, but different enough so that many testing procedures have different articles and numbers. As of late 2011, most rugged manufacturers have switched to providing ruggedness testing information using MIL-STD-810G, but some still cite the older standard.

What's MIL-STD-810F Method 506.4 (Rain)?

Manufacturers often refer to MIL-STD-810F Method 506.4. The MIL-STD-810F is a Department of Defense document that describes test methods for environmental engineering considerations and lab tests in great detail (Note that MIL-STD-810G, issued October, 2008, has superseded MIL-STD-810F). Method 506.4 describes testing to determine how well a piece of equipment is protected from rain, water spray, and dripping water.

Procedure I tests resistance to rain and blowing rain, with variations up to 45 degrees from the horizontal.

Procedure II sprays all exposed surfaces with water for not less than 40 minutes per face.

Procedure III drips water from no less than 3 feet for 15 minutes.

What's MIL-STD-810F Method 509.4 (Salt Fog)?

Salt fog can quickly ruin equipment. 509.4 describes testing methods to determine the effectiveness of protective coatings and finishes on materials for corrosion, electrical effect and physical effects. It can also determine the effects of salt deposits on the physical and electrical aspects of materiel. The product is exposed to salt fog mist from a 5% salt solution via atomizers at about 95 degrees Fahrenheit for a minimum of four alternating 24-hour periods, two wet and two dry. The product is then examined for salt deposits that can clog or bind components, electrical malfunction, and potential short and long-term impact of any observed corrosion.

What's Intrinsic Safety?

Intrinsic safety is a requirement that may be applicable to devices that are being operated in areas with flammable gases or fuels. It means that the device is incapable of igniting those gases. In short, an intriniscally safe piece of equipment won't ignite flammable gases, See our Intrinsic Safety page, and for more detail ecom instruments' intrinsic safety section and our HazLoc Primer prepared in conjunction with BARTEC.

What's MIL-STD-810F Method 510.4 (Sand and Dust)?

Specs also often include references to MIL-STD 510.4. Those are tests that evaluate the ability to resist the effects of dust that may obstruct openings, penetrate cracks, crevices, bearings, and joints and to evaluate the effectiveness of filters.

Procedure I tests if the device can keep out blowing dust.

Procedure II determines if it is sealed against blowing sand.

Procedure III tests what happens if dust settles on the computer as that can affect heat dissipation or clog up filters.

What's MIL-STD-810F Method 516.5 (Drop)?

MIL-STD-810F 516.5 also often appears in ruggedness specs. This tests a device's ability to survive a variety of impacts and shocks. MIL-STD-810F Method 516.5 defines the purpose of the shock test to "provide a degree of confidence that materiel can physically and functionally withstand the relatively infrequent, non-repetitive shocks encountered in handling, transportation, and service environments."

Procedure IV -- Transit Drop -- is especially popular with rugged computing equipment vendors and commonly called "drop test" or "drop spec." The test requires that items weighing 100 pounds or less survive a total of 26 drops on each face, edge and corner. The 26 drops an be divided among up to five samples of the same test item, which probably means used the first until it fails, then start with the second, and so on, although the language is not clear. Drop distance generally depends on "how materiel in the field might commonly be dropped." Table 516.5-VI (Transit Drop Test) shows that items weighing less than 100 pounds with a largest dimensions of less than 36 inches, i.e. virtually all mobile computers, must be dropped from 48 inches because "a light item might be carried by one man, chest high; thus it could drop 122 cm (48 inches). It also appears that the test is conducted with the equipment off.

While most manufacturers test using Procedure IV (Transit Drop), testing according to other procedures might make more sense:

  • Procedure I (functional shock) test is designed to "test materiel (including mechanical, electrical, hydraulic, and electronic) in its functional mode and to assess the physical integrity, continuity and functionality of the materiel to shock." It also says that the intent of Procedure I is to disclose equipment malfunction that may result from shocks experienced by materiel during use in the field. Eben though materiel has successfully withstood even more severe shocks during shipping or transit shock tests, there are differences in support and attachment methods and in functional checking requirements that make this test necessary. A shock apparatus is used and equipment must remain functional with a sawtooth pulse of at least 40G for 11ms (truck/vehicle-mounted 20G).
  • Procedure III (fragility) is designed "to determine the maximum level of input to which the materiel can be exposed and still continue to function...". In Procedure III, drop height is defined as "the height from which the materiel might be dropped in its shipping configuration and be expected to survive." "Suggested drop height" for items up to 20 pounds is 30 inches.

Realize that all these MIL-STD-810F 516.5 procedure were really designed to measure the effectiveness of packaging, so applying this to dropping actual devices is a bit of a reach. And simply stating that a device is "tested according to MIL-STD-810F" by itself means nothing. Detailed explanation as to what was tested and what the outcome was must be included, and as a minimum, Procedures I and IV should have been done and passed.

Note that according to the DOD, field data suggests that a typical piece of equipment will be dropped from heights up to four feet an average of four to six times during its life cycle.

What other MIL-STD-810F tests are there?

The MIL-STD-810F is a very comprehensive document. As a result, a statement saying a device is "MIL-STD-810F tested" doesn't provide enough information. The MIL-STD-810F is an almost 600 page document with tests for about two dozen things that can affect a piece of equipment. The tests are:

  • 500.4 Low Pressure (Altitude)
  • 501.4 High Temperature
  • 502.4 Low Temperature
  • 503.4 Temperature Shock
  • 504 Contamination by Fluids
  • 505.4 Solar Radiation (Sunshine)
  • 506.4 Rain
  • 507.4 Humidity
  • 508.5 Fungus
  • 509.4 Salt Fog
  • 510.4 Sand and Dust
  • 511.4 Explosive Atmosphere
  • 512.4 Immersion
  • 513.5 Acceleration
  • 514.5 Vibration
  • 515.5 Acoustic Noise
  • 516.5 Shock
  • 517 Pyroshock
  • 518 Acidic Atmosphere
  • 519.5 Gunfire Vibration
  • 520.2 Temperature, Humidity, Vibration, and Altitude
  • 521.2 Icing/Freezing Rain
  • 522 Ballistic Shock
  • 523.2 Vibro-Acoustic/Temperature
Each test has various procedures and methods, and each may or may not be relevant to a particular application. Major rugged equipment manufacturers have their own testing labs where they can conduct MIL-STD-810F testing. This is generally done in conjunction with testing in an independent lab.

What is the MIL-STD-3009?

MIL-STD-3009 (also referenced as DOD-STD-3009) is another standard manufacturers of rugged equipment may refer to. It sets requirements for aircraft display equipment for use with night vision imaging systems. For mobile computers that generally means they must not interfere with night vision equipment in a cockpit.

Part of this document is the U.S. Navy MIL-HDBK-87213 Revision A (Electronically/Optically Generated Airborne Displays) that describes, among other, criteria for legibility of electro-optical display equipment and daylight readability in bright environments, which is a military requirement. This can be an issue with daylight readable displays marketed to the govenment and armed forces.

What is ASTM 4169?

At times, rugged product descriptions refer to ASTM 4169, Truck Transport, 11.5.2 Random test, Assurance Level 2. ASTM stands for American Society for Testing and Materials and the 4169 standard sets tests and requirements for strength, durability and protective capability of packaging. Level II stands for medium test intensities (Level I is highest and Level II lowest) and is most commonly used.

What is the MIL-STD-461E?

MIL-STD-461E establishes interface and associated verification requirements for the control of the electromagnetic interference (emission and susceptibility) characteristics of electronic, electrical, and electromechanical equipment and subsystems designed or procured for use by activities and agencies of the Department of Defense. The standard primarily applies to electronic enclosures no larger than an equipment rack, electrical interconnections between enclosures, and electrical power inputfrom prime power sources.

Rugged computer manufacturer AMREL created a useful white paper on MIL-STD-461E here.

What is UL 1604?

You may come across references to UL 1604. This is not a governmental or industry association standard, but a certification by Underwriters Laboratories Inc. UL is an independent product safety certification organization that has been testing products and writing standards for product safety for over a century. They have over 60 testing labs and have develped over 1000 standards. UL 1604 is a certification document and covers equipment, circuits, or components intended for use in hazardous locations. This basically deals with a unit's safeguarding against causing ignition of specified flammable gas- or vapor-air mixtures.

What does "embedded" mean?

There are various definitions. "Embedded" is often used for products or projects where the computer is just part of a larger system, and not a standalone PC. Intel uses the term differently. For them, "Embedded indicates that Intel anticipates shipping the product for an extended period of time. Embedded parts typically need to be procurable for 7+ years, whereas standard parts are typically procurable for 2+ years."

What is "PCI compliance"?

In the payment processing industry, PCI stands for "Payment Card Industry." The PCI has the "Payment Card Industry Data Security Standard" (PCI DSS), which is a set of requirements designed to ensure that all companies that process, store or transmit credit card information maintain a secure environment. PCI also issued the Payment Card Industry Security Standards Council (PCI SSC) to cover the ongoing evolution of the transaction process. See the PCI Compliance Guide here.

Why is altitude testing important?

Testing procedures designed to ascertain the ability of a piece of equipment to operate at high altitude are described in MIL-STD-810G Method 500.5 2.3.1 b(1). However, that test arbitrarily uses 15,000 feet, which is more than the 7,000 feet atmospheric pressure in a commercial airplane, but a good 2,000 feet less than even Mt. Everest's base camp. Why does it matter whether a piece of rugged computing equipment can operate in high altitude? Because at 19,000 feet, air pressure drops to half from what it is at sea level, meaning there are half the air molecules available for cooling and any other operation that requires air pressure for normal functioning.

What is the difference between OEM and ODM?

OEM stands for Original Equipment Manufacturer and describes a company that designs products according to their own specifications, builds them, but the products are then sold by another company undert that company's name or brand.

ODM stands Original Design Manufacturer and describes a company that builds a product based on another company's design and specifications.

Active vs passive digitizers
What does "rugged" mean?
Rugged Specs Primer
FIPS 201
Intrinsic Safety
NEMA Ratings
NVIS standards
IEC 60601
IP Rating
RFID vs. Bar Code
RFID viruses and worms
Outdoor-readable screens 2007
PCI compliance
UL 1604
Wide-angle LCDs '04
Specification documents
MIL-STD-810F download page
MIL-STD-810G download page
Helpful links
QSI/Beijer rugged page