Rugged computers are more than just 'hard shells'

Even professional users of rugged laptops, tablets and smartphones are sometimes unsure of what defines a ‘rugged computer’ and how the various tests to validate ruggedness are carried out. A truly rugged computer is so much more than just a normal computer wrapped in a tough outer case, as Handheld’s CEO Jerker Hellström explains.

Firstly, let's distinguish between a ‘rugged’ computer and a ‘ruggedised’ computer (or tablet or smartphone). A rugged device is designed to operate reliably in very harsh environments and conditions. The term ruggedised gives the sense that fragile internal components are somehow protected, but truly rugged devices are not simply wrapped in a tough shell.

Tough and durable mobile devices are gaining in popularity as customers demand more durable products. There are some mainstream devices that could be described as ruggedised and are advertised as such, without being truly rugged.

To meet the true definition:

• Devices should have passed MIL-STD tests, ie, the American military standard. 24 laboratory test methods ensure that equipment can handle low pressure at high altitudes; exposure to extreme temperatures; rain; humidity; sand and dust exposure; leakage; shock and vibration.
• They must be highly rated on the ingress protection (IP) scale for protection against dust and liquids. Ratings are displayed as a 2-digit number where the first digit reflects the level of protection against dust and the second against liquids (water).

Rugged computer tests should include:

Drop and shock testing

This is one of the most important tests, simply because devices are dropped all the time. Drop a normal computer and you will break the display or the hard drive. Drop a rugged computer and nothing will happen - if it has passed all the relevant tests.

Rugged devices are tested to ensure they can survive falls as well as high-force impacts. Drop tests are certified by independent test laboratories and performed in accordance with MIL-STD-810G. There are eight different procedures to choose from that each use different ways to cause shock or impact. The ‘transit drop test’ is the most cited and requires items to survive a total of 26 drops from the height of 122 cm, on each face, edge and corner, onto a hard surface like concrete.

Liquid resistance testing

Mobile field computers are inevitably exposed to rain, spills and splashes. The second number of the IP code describes the liquid ingress protection, ie, how well the unit is protected against water. The scale ranges from dripping water to continuous immersion in water. Water resistance tests are often carried out by the manufacturers of rugged computers by exposing the computer to powerful water jets from many directions. The test duration, water volume and water pressure vary depending on the rating.

Vibration testing

Ordinary mobile devices are sensitive to vibrations and hard drives are especially vulnerable. Rugged computers must be able to withstand vibrations as they are often used in vehicles that travel on bumpy and rough surfaces.

Vibration tests are performed in accordance with MIL-STD-810G. The tests use laboratory shakers set to different levels to simulate being on a vehicle or carried by a person, with variations in the vibrations’ wave form, frequency and intensity depending on the type of device and the environment being simulated.

Sand and dust testing

A rugged computer must be able to keep out particles. Field workers are often exposed to dust and dirt that would slow key functions and damage components if not protected.

Dust resistance procedures test ingress of small particles. Flour and sand are projected onto the device at high wind speeds and high temperatures for several hours, while rotating the device and varying the temperature and wind speed.

Extreme temperature testing

Rugged computers must handle extreme temperatures and wild temperature swings. High- and low-temperature tests are conducted in accordance with MIL-STD-810G. When testing for high-temperature operability, the device is exposed while it is turned off (storage), while being turned on and used (operation) and how it works back at operational temperatures after high-temperature exposure (tactical-standby to operational).

Testing for low temperatures employs similar methodology, but in freezing conditions.

Humidity testing

In addition to liquid resistance testing for IP rating, many manufacturers test their devices in highly humid conditions as defined by MIL-STD-810G. Computers are exposed to humidity well over 90% for several days in tropical heat. Many of the same features that make mobile computers liquid resistant also help prevent damage from high humidity.

How do manufacturers make devices tough enough?

• As opposed to normal computers, most rugged computers have no moving parts like fans or rotating hard drives. They generally have solid-state drives, which are more resistant to physical shock.
• Stiffeners, often made out of aluminium, prevent inside components and boards from flexing during an impact. The outer shell and bumpers are designed to absorb the energy from a drop to prevent internal damage.
• Non-rugged smartphones and computers feature a glass screen with coating that makes them sensitive to touch. Displays on rugged computers use chemically strengthened glass to protect against scratches and cracks and can be positioned lower than the surrounding case to decrease vulnerability.
• A display backlight is used to improve outdoor readability, even in direct sunlight.
• Some rugged computers are fitted with internal heaters in order to operate successfully in very cold environments. The heater warms components to an acceptable operating level and eliminates condensation arising from temperature swings.

In short, every simple detail and small part is researched, developed and chosen to make the computer as rugged as possible.

While it is important to know the ingress protection scale (the higher the numbers, the tougher the device), it is also instrumental to check that the unit has undergone MIL-STD tests. Many devices boast good IP numbers but fail to inform customers that they have not gone through any MIL-STD tests, which basically makes them normal fragile computers that are somewhat dust and water resistant.

With a deeper understanding of the standards and the tests, it will be easier to choose the mobile rugged device that suits your unique needs. And if you want a rugged computer then do not buy a ruggedised computer. Rugged computers are built - inside and out - to be rugged. No fragile parts wrapped in a hard shell here.

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