Consumer-grade vs Rugged PCs

Why should you buy a rugged notebook, tablet PC or handheld computer over a consumer grade system? The below article offers information about industry terms, hardware features, the history and trends in this computer market niche. The IP and MIL-STD standards provide objective information to help you select a rugged computer that will stand up to your everyday 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 a computer. The IP rating uses two numbers to describe how well the unit is protected against incursion by dust and water. The first number (1 to 6) measures dust protection; the second number (1 to 8) describes water protection.
The second major standard MIL-STD-810F is a series of U.S. military testing standards that have gained acceptance in industries beyond the military for their methods of objectively determining whether a device is able to withstand potentially destructive elements such as drops, dust, water immersion, vibration, and altitude or temperature extremes.

Consumer-Grade Computers

Throughout this document it is important to remember that consumer-grade computers have no IP rating and are not rated to MIL-STD-810F. They are not designed to withstand any kind of substantial shock or drop and cannot ideally be used in any environment outside of an office.

Semi-Rugged Computers

Semi-rugged systems can handle rougher treatment than a consumer-grade computers but they are not fully waterproof or dustproof, generally have a narrower temperature range, and do not meet all MIL-STD-810F specs. Most semi-rugged computers have a lower IP rating. This 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.

Fully Rugged Computers

At Steatite Rugged we can offer a range of fully rugged systems which are sealed against dust and moisture, and in some cases can even survive temporary immersion provided the IP rating is high enough. They have also passed a full battery of MIL-STD-810F tests, including drops, vibration, immersion and temperature extremes and are rated to at least IP54 or higher.

IP Ratings

The Ingress Protection (IP) Rating, 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: Fully rugged computers generally have an ingress protection rating of IP54 or above. That means dust cannot get inside the enclosure, and IP67-rated units can even survive temporary immersion, such as being dropped in a puddle.

MIL-STD-810F

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.
When considering purchasing a rugged computer it’s important to know more about the actual tests which have been undertaken on the system. This is what truly differentiates a semi and fully rugged product from a consumer-grade system We have described the relevant MIL-STD-810 tests below.

MIL-STD-810F Method 500.4 - Low Pressure

Low-pressure (altitude) chamber tests determine if material can withstand and operate in a low pressure environment. The test also determines if material 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 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 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 material. As a result, exposing a consumer grade system to low temperatures may either temporarily or permanently impair the operation of the unit by changing the physical properties of
its casing and components. Therefore, a rugged system which has undergone a lowtemperature test must be considered whenever the equipment 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
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 a unit. Temperature-shock tests are conducted on rugged computers to determine if material can withstand sudden changes in temperature
without experiencing physical damage or deterioration in performance. Some problems that might occur on a consumer-grade notebook 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
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 on a non rugged laptop 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 mould/mildew
· moisture penetration that changes material properties
· condensation that affects electrical or mechanical performance

Some problems apparent on consumer grade systems 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.

Sand and dust ingress on a consumer grade notebook or tablet PC will inhibit performance by blocking ventilation and causing the system to overheat. This problem is not apparent on fully rugged notebooks.

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 may be used in place of the rain test (Method 506.4) to verify that a unit is watertight. This is acceptable provided the material 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 on systems which do not have a Mil-Std 810F rating 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 material 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 rugged mobile computer systems is making them increasingly useful. Building ruggedness into normally fragile computer 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 rugged mobile computer that will stand up to your working environment requirement. For true outdoor computing longevity and reliability, units must achieve a rating of IP54 and have been successfully tested against the most relevant MIL-STD-810F procedures.

To find out more, or discuss your specific requirements, call us on +44(0)1527 512400, drop us an email at sales@rugged-systems.com or download our Steatite Company Overview for more information on all our capabilities.

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