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What is Rugged?

Explaining the ruggedness testing standards

Handheld computers are becoming increasing popular for use outside the office. Their versatility makes them useful tools for public safety, law enforcement, field service, and construction, as well as utility, forestry and military applications.

However, consumer-grade handhelds like Hewlett Packard iPAQs and Palm Pilots are not meant for everyday use outdoors. They’re not designed or built for applications where users often work in rain, extreme heat or cold and at job sites that are dusty, wet or muddy. Nor can consumer-grade handhelds withstand repeated drops or vibration. For these harsher environments and for rough everyday use, fully rugged and semi-rugged handhelds are much better choice.

This white paper explains the difference between semi-rugged and rugged handhelds, define IP and MIL-STD durability standards, and describe the testing protocols.  The IP and MIL-STD standards provide objective information to help you select a handheld computer that will stand up to your users’ working environments.

IP Ratings and MIL-STD-810F

Two basic standards-Ingress Protection (IP) ratings and MIL-STD-810F-are used to determine the ruggedness of handheld computers. The IP rating uses two numbers to describe how well the unit is protected against dust and water. The first number (1 to 6) measures dust protection; the second number (1 to 8) describes water protection.

Semi-Rugged Handhelds

Semi-rugged handhelds can handle rougher treatment than a consumer-grade handheld, but they are not fully waterproof or dustproof. Most semi-rugged handhelds come with an IP rating of IP54. That means the unit is protected, though not sealed, against dust. It is resistant only to light splashing, but it’s not able to withstand jet sprays or immersion. Some, but not all semi-rugged handhelds also meet some of the MIL-STD-810F standards, though not those for immersion or dust.

Ultra Rugged Handhelds

Ultra rugged handhelds come with an IP67 rating, which means they are sealed against dust and can survive temporary immersion. They have also passed a full battery of MIL-STD-810F tests, including drops, vibration, immersion and temperature extremes.

IP Codes

The Ingress Protection (IP) Code, prepared by the International Electrotechnical Commission (IEC), is a system for classifying the degrees of protection provided by the enclosures of electrical equipment. The system was intended to establish a uniform method for describing the protection provided by the enclosure. The numbers in the IP code describe the various levels of protection as outlined below:

The Ingress Protection (IP) Coding

As described earlier, most semi-rugged handhelds have rating of IP54. That means the unit is protected, but not sealed, against dust and is splash protected. M3 has got an IP64 rating. That means dust cannot get inside the enclosure, and the unit can survive sprays of water.

The MIL-STD

The MIL-STD testing procedures determine the effect of natural and artificial impact on equipment. Started in 1961, MIL-STD-810 has seen six revisions over the past 45 years. Product data sheets often make claims like “designed using MIL-STD-810 test procedures.” Since MIL-STD-810 includes hundreds of testing procedures, each of which tests different types of protection, the mere reference to MIL-STD-810 testing is insufficient. It’s important to know which MIL-STD-810 tests were performed on the unit to determine how rugged it truly is.

We've described the relevant MIL-STD-810 tests below.

MIL-STD-810F Method 500.4-Low Pressure

Low-pressure (altitude) chamber tests determine if materiel can withstand and operate in a low-pressure environment. The test also determines if materiel can withstand rapid pressure changes. Some problems that might occur after exposure to reduced pressure are:

  1. Rupture or explosion of sealed containers
  2. Change in the physical and chemical properties of low-density materials
  3. Erratic operation or malfunction of equipment resulting from arcing or corona
  4. Overheating of equipment due to reduced heat-transfer properties
  5. Failure of hermetic seals

MIL-STD-810F Method 501.4-High Temperature

High temperatures may temporarily or permanently impair the performance of a handheld computer by changing the physical properties or dimensions of its casing as well as internal components. Some problems that might occur after exposure to high temperature include:

  1. Parts binding due to materials expanding at different rates
  2. Materials changing in dimension, either totally or selectively
  3. Permanent gasket deformation
  4. Deterioration of closure and sealing strips
  5. Changes in the value of fixed-resistance resistors
  6. Variations in electronic circuit stability caused by materials expanding at different rates.
  7. Overheating transformers and electromechanical components
  8. Shortened operating lifetime
  9. High pressures created within sealed cases
  10. Discoloration, cracking or crazing of organic materials

MIL-STD-810F Method 502.4-Low Temperature

Extremely low temperatures have adverse effects on almost all basic materiel. As a result, exposing test items to low temperatures may either temporarily or permanently impair the operation of the test unit by changing the physical properties of its casing and components. Therefore, low temperature test must be considered whenever the test item will be exposed to temperatures below standard ambient. Some problems that might occur after exposure to extreme cold include:

  1. Materials becoming hard and brittle.
  2. Parts binding due to materials expanding at different rates in response to temperature changes
  3. Changes in electronic components such as resistors and capacitors
  4. Stiffening of shock mounts
  5. Reduced material strength from cracking and crazing
  6. Static fatigue of restrained glass
  7. Water and moisture condensing and freezing

MIL-STD-810F Method 503.4-Temperature Shock

Exposure to sudden, extreme temperature changes may temporarily or permanently affect the operation of the unit. Temperature shock tests are conducted to determine if materiel can withstand sudden changes in temperature without experiencing physical damage or deterioration in performance. Some problems that might occur after exposure to sudden temperature changes include:

  1. Glass shattering
  2. Moving parts binding or slackening
  3. Component separation, deformation or facture
  4. Stiffening of shock mounts
  5. Changes in electronic components
  6. Electronic or mechanical failures due to rapid water condensation or freezing
  7. Materials expanding or contracting at different rates in response to temperature changes.
  8. Surface coatings cracking
  9. Sealed compartments leaking

MIL-STD-810F Method 506.4-Rain

The rain test is conducted to determine if the protective covers or cases effectively prevent rain from penetrating the unit. The rain test also determines if the unit can satisfy its performance requirements during and after exposure to rain. Some problems that might occur after exposure to rain include:

  1. Loss of physical strength
  2. Metal corrosion
  3. Surface coatings deterioration
  4. Electrical component malfunctions

MIL-STD-810F Method 507.4-Humidity

Moisture can cause multiple types of physical and chemical deterioration. These include: surface effects such as corrosion and organic growth such as mold and mildew; moisture penetration that changes material properties; and condensation that affects electrical or mechanical performance. Some problems that result from exposure to a warm, humid environment include:

  1. Swelling of materials due to moisture absorption
  2. Loss of physical strength
  3. Changes in mechanical properties
  4. Degradation of electrical and thermal properties in insulating materials
  5. Electrical shorts due to condensation
  6. Moving parts binding due to corrosion or fouling of lubricants
  7. Metal oxidation and/or galvanic corrosion
  8. Loss of plasticity
  9. Accelerated chemical reactions

MIL-STD-810F Method 510.4-Sand and Dust

The sand and dust test is divided into two procedures. The small-particle procedure (dust and fine sand) is performed to determine the ability of equipment to resist the effects of dust particles that may penetrate into cracks, crevices and joints. The blowing sand test is performed to determine the ability of equipment to be stored and used under blowing sand conditions. To pass the blowing sand test, there must be no loss of in performance, effectiveness, reliability, and maintainability due to the abrasion (erosion) or clogging effect caused by large, sharp-edged particles. Examples of some problems that could occur as a result of exposure to sand and dust are:

  1. Surface abrasion
  2. Seal penetration
  3. Surface erosion
  4. Degradation of electrical circuits
  5. Clogging of openings and filters
  6. Physical interference with mating parts
  7. Moving parts binding or fouling

MIL-STD-810F Method 512.4-Immersion

The immersion test is conducted on operating and non-operating units that may be exposed to partial or complete immersion. In some cases this test maybe used in place of the rain test (Method 506.4) to verify a unit is watertight. This is acceptable provided the materiel configuration would be the same for both situations, and the method of water ingress is well understood. However, there are documented situations where the impact of the spray causes a pumping of water across the seals during the rain test. This does not occur in the immersion test, where the seals are held tight against a backing plate by the static pressure. For this reason, both the rain and immersion tests should be performed.

Penetration of water into materiel or packaging enclosures can result in multiple problems. Consider the following typical problems to help determine if this method is appropriate for the equipment being tested. This list is not intended to be all inclusive.

  1. Fouling of lubricants between moving parts
  2. Formation of electrically conductive paths that may cause electrical or electronic equipment to malfunction or become unsafe to operate
  3. Corrosion due to direct exposure to the water or due to the high relative humidity levels

MIL-STD-810F Method 514.5-Vibration

Vibration testing is performed to determine the resistance of equipment to stress caused by vibration during shipment and in typical application environments. Problems caused by vibration include:

  1. Wire chafing
  2. Loosening of fasteners
  3. Intermittent electrical contacts
  4. Touching and shorting of electrical parts
  5. Seal deformation
  6. Component fatigue
  7. Display/touchscreen misalignment
  8. Cracking and rupturing
  9. Excessive electrical noise

MIL-STD-810F Method 516.5-Shock

Shock tests are performed to assure that materiel can withstand the relatively infrequent, non-repetitive shocks or transient vibrations encountered in normal use and transport. Shock tests are also used to measure an item’s fragility, so that packaging may be designed to protect it if necessary. Mechanical shocks will excite an item to respond at both forced and natural frequencies. This response, among other things, can cause:

  1. Failures due to increased or decreased friction, or interference between parts
  2. Changes in dielectric strength, loss of insulation resistance and variations in magnetic and electrostatic field strength
  3. Permanent deformation due to overstress
  4. More rapid material fatigue.

Making an informed decision

The versatility of today’s handheld computers is making them increasingly useful. Building ruggedness into normally fragile computers parts extends their reach and increases their utility in applications where users and their equipment are subjected to outdoor conditions. The IP and MIL-STD standards provide objective information to help you select a handheld computer that will stand up to your users’ working environments.