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Understanding ‘rugged’ computers

article image Jerker Hellström

Handheld Group CEO Jerker Hellström explains the meaning of ‘rugged computers’, saying that the term goes much beyond a normal computer wrapped in a tough outer case.

Even professional users of rugged laptops, tablets and smartphones are sometimes unsure of what defines a ‘rugged computer’, or the various tests conducted to validate ruggedness in a device.

To begin with, the perception of a ‘rugged computer’ is that of a device designed to operate reliably in very harsh environments and conditions, while ‘ruggedised’ gives the sense that fragile internal components have extra protection. However, truly rugged computers are much more than a device simply wrapped in a tough shell.

Customers are increasingly demanding tough and durable mobile computers and smartphones, and there are actually some mainstream devices that could be described as ruggedised. Though advertised as ruggedised, they are not truly rugged; except for a waterproof construction, these devices lack other aspects of ruggedness such as the ability to withstand vibrations and shocks, or perform well in extreme temperatures.

For a computer to be rugged, the devices should have passed some of the MIL-STD tests, the American military standard for equipment. Twenty four laboratory test methods determine whether the equipment can handle low pressure at high altitudes; exposure to high and low temperatures plus temperature shocks; rain; humidity; sand and dust exposure; leakage; and shock and vibration.

Secondly, they must be highly rated on the IP scale for protection against ingress of dust and liquids. The ratings are displayed as a two-digit number with the first digit reflecting the level of protection against dust and the second digit representing the level of protection against liquids.

Tests for determining the ‘rugged’ factor in rugged computers

Drop and shock testing

One of the most important tests for ruggedness, all rugged mobile computers are tested to ensure they can survive falls as well as high-force impacts to the device’s casing. Drop tests are certified by independent test laboratories and performed in accordance with MIL-STD-810G. From the eight different procedures available to cause shock or impact, the transit drop test is the most preferred and requires items to survive a total of 26 drops from a height of 122cm onto a hard surface such as concrete.

Liquid resistance testing

The IP rating for mobile field computers, which indicates liquid ingress protection, is an important factor when choosing these devices as they are inevitably exposed to rain, spills and splashes. The second number of the IP code describes the liquid ingress protection. Water resistance tests expose the computer to powerful water jets from many directions without harmful effects, with the test duration, water volume and water pressure varying depending on the rating.

Vibration testing

Unlike ordinary mobile computers that are not built to handle vibrations, rugged computers must be able to handle vibrations since they are often used in vehicles travelling on bumpy surfaces. Performed in accordance with MIL-STD-810G, vibration tests help determine if a device can withstand vibrations. 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

Dust ingress is also an important factor that may impact the performance of a rugged computer slowing down key functions and damaging components. The dust resistance procedure tests ingress of small dust particles with flour and sand projected onto the device at high wind speeds and high temperatures for several hours, rotating the device and varying the temperature and wind speed.

Extreme temperature testing

Rugged mobile computers must also be able to withstand extreme temperatures. High temperature and low temperature tests are conducted in accordance with MIL-STD-810G with the devices being exposed to high and low temperatures in all stages of operation.

Humidity testing

Manufacturers of rugged mobile computers test their devices in highly humid conditions as a separate test defined by the MIL-STD-810G standard. The computers are exposed to humidity well over 90 per cent for several days in tropical heat.

Manufacturers of rugged mobile computers have to make their devices tough enough to pass these tests. Some of these design initiatives include using a no-moving parts design, using solid state drives instead of rotating hard drives, placing stiffeners inside the rugged computer to prevent inside components and boards from flexing during an impact; designing outer shell and bumpers to absorb the energy from a drop to prevent internal damage; using chemically strengthened glass to prevent scratches and cracks on the touchscreen displays; positioning displays lower than surrounding case to decrease vulnerability; using display backlight to improve outdoor readability, even in direct sunlight; and fitting internal heaters to operate successfully in very cold environments.

Professional users of rugged computers must therefore consider factors such as the IP rating and performance on the MIL-STD tests before investing in these devices. Most importantly, choose a rugged computer and not a ‘ruggedised’ device because rugged computers are built to be rugged inside and out. 

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