Mobile computing devices are increasingly being used in non-traditional computing environments. These non-traditional computing environments often place harsh demands on electronic equipment.
Mobile computing devices, as defined in this article, include laptops, tablet or notebook PCs and handheld devices / PDAs. The commonly used versions of these devices are typically referred to as consumer editions. These commonly used versions are available at consumer electronics stores and computer retail stores and can be fine for personal and office-like indoor professional use.
In many cases, enterprise and industrial mobile computing devices are required to be tolerant of extreme temperatures, being routinely dropped, moisture in the form of humidity or rain or full submersion in water, sand or dust and for some uses must be capable of operating in highly flammable environments.
In this article we cover the different specifications for devices designed to operate under these “rugged" conditions, and we provide some insight into the types of questions that you will need to ask when selecting a mobile device for enterprise or industrial use.
The five key criteria that distinguish an enterprise or industrial computing device from a consumer edition of an equivalent device are:
tolerance of extreme temperatures
tolerance of being dropped routinely (impact and vibration resistance)
resistance to moisture
resistance to dust and sand
ability to operate in highly flammable environments (intrinsic safety rating)
As you might imagine, different device types, and even different models of similar devices from the same manufacturer will perform at different levels for these 5 criteria.
You will often see different manufacturers describe their mobile computing devices as rugged, semi-rugged, enterprise-class, industrial class or a myriad of other names. As these terms can mean different things from different manufacturers, we must resort to device comparison using the various specifications defined by standards bodies.
The military originally defined a standard, MIL-STD-810, that many manufacturers will refer to. The MIL-STD provides a large number of tests and testing methods to determine the effect of natural and artificial impact on equipment. Many mobile device manufactures often state that their rugged devices were designed using MIL-STD-810 test procedures. Since there are hundreds of procedures in this spec and they test different degrees of protection, the mere reference to MIL-STD-810 provides very little information.
If we limit our focus to the 5 criteria defined above, there are other specifications that are almost always readily available from the manufacturer of rugged mobile computing devices that can be used to perform a consistent evaluation across device types and across different manufacturers.
These specifications are:
Temperature specification
Drop specification
Ingress Protection (IP) or alternatively a NEMA specification for water and dust resistance
I-Safe specification for flammable environments
Temperature Specification
All ruggedized computers will include operating and storage temperature specifications. Industrial strength computers can be exposed to extreme temperatures, especially if a device is used outside, or in a freezer (cold storage) environment. Cold storage environments usually require that a device operate in -30C (-22F) temperatures. In order for a device to successfully operate in this extremely cold environment, an internal heater is usually required. The heater warms components to an acceptable operating level and eliminates condensation when exiting the cold storage environment and entering a warmer environment. Conformal coatings are also used to eliminate condensation build-up on internal components.
Drop Specification
All handheld or laptop computers should include a drop specification that describes the device's ability to withstand the shock of a fall to a hard surface. For obvious reasons, the drop specification is extremely important for mobile computers and cannot be overlooked. If a device cannot withstand a drop from a reasonable distance, then its life will be extremely short. Most ruggedized handheld computers can withstand a 4-foot drop to concrete.
Ingress Protection (IP)
Ingress Protection (IP) ratings consist of a single number, such as IP45, and classify the degree of protection provided for electrical equipment by enclosures. The first number indicates, on a scale from 0 to 6, the protection against solid objects penetrating the housing. The second number gives, on a scale from 0 to 8, protection against penetration by liquids. For both numbers, a 0 means no protection and the highest number maximum protection.
IP Rating
Dust Protection (1 st number)
0 No protection
1 Puncture protected against objects > 50mm (hands)
2 Puncture protected against objects > 12mm (fingers)
3 Puncture protected against objects > 2.5mm (tools/wires)
4 Puncture protected against objects > 1mm (small tools)
5 Protected against dust, limited ingress
6 Totally protected against dust
Liquid Penetration (2 nd number)
0 No protection
1 Protection against dripping water or condensation
2 Protection against water spray 15 degree from vertical
3 Protection against water spray 60 degree from vertical
4 Protection against water spray from all directions
5 Protection against low pressure jets of water
6 Protected against heavy seas
7 Protection against the effects of immersion
8 Protected against immersion
NEMA (an alternative to IP Specification)
The National Electrical Manufacturers Association (NEMA) provides yet another classification system. NEMA 250 describes a variety of different enclosures and how they hold up against different environmental impact. NEMA enclosure types are described at www.nema.org/engineering/papers/enclosure.html and shows both NEMA and IP250 protection ratings and how they relate.
1 Indoor protection against limited amounts of falling dirt.
2 Indoor protection against limited amounts of falling water and dirt.
3 Outdoor protection against rain, sleet, wind blown dust and damage from external ice formation.
3R Outdoor protection against rain, sleet, and damage from external ice formation.
3S Outdoor protection against rain, sleet, windblown dust and to provide for operation of external mechanisms when ice laden.
3X Indoor or outdoor use primarily to provide a degree of protection against windblown dust and rain, splashing water, hose-directed water and damage from external ice formation.
4X Indoor or outdoor use primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, hose-directed water, and damage from external ice formation.
5 Indoor protection against settling airborne dust, falling dirt, and dripping noncorrosive liquids.
6 Indoor or outdoor protection again hose-directed water, and the entry of water during occasional temporary submersion at a limited depth and damage from external ice formation.
6P Indoor or outdoor protection against hose-directed water, the entry of water during prolonged submersion at a limited depth and damage from external ice formation.
7 Indoor use in hazardous locations as defined (Commonly referred to as explosion-proof).
8 Indoor or outdoor use in hazardous locations (commonly referred to as oil immersed.
9 Indoor use in hazardous locations (commonly referred to as dust-ignition proof).
10 Meets the requirements of the Mine Safety and Health Administration (MSHA).
12/K Indoor protection against circulating dust, falling dirt, and dripping noncorrosive liquids.
13 Indoor protection against dust, spraying of water, oil, and noncorrosive coolant.
Intrinsically Safe Specifications
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 an intriniscally safe device will not ignite flammable gases. ISA-RP12-6 defines intrinsically safe equipment as "equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited concentration." Intrinsically safe areas are hazardous environments where flammable gases, vapors and liquids are stored and manufactured. These areas are prevalent in many of today's manufacturing facilities including chemical plants, paint manufacturers, oil refineries, textile mills, etc.
Rugged Devices
Several companies specialize in the manufacture of rugged devices and some also support options for wide area wireless capabilities (ether CDMA/EVDO or GSM/GPRS/UMTS). For laptops and notebook computers, these include the GoBook series from Itronix, the ToughBook series from Panasonic, the MobileForce series from Getac, the Lattiude ATG D620 from Dell, the nr3600 from HP Compaq and the Rough Rider series from Rugged Notebooks. For handheld devices / PDAs, the Dolphin series from Handheld, the GoBook Q-200 from Itronix, the ToughBook P1 from Panasonic, the Workabout Pro from Psionteklogix, the 700 series class of handhelds from Intermec and the CN3 and MC70 from Motorola (Symbol) are based on phone editions of Pocket PC and offer optional GSM/GPRS or CDMA/EVDO capabilities.
Summary
In this article, we have described 5 criteria that can be used to compare rugged mobile computing devices. Rugged computing devices are built to withstand moisture, dust, extreme temperatures, dropping and vibrations. Some devices can operate in highly flammable environments. We have provided specifications that can be used to determine the degree to which rugged devices can tolerate these circumstances.
Not all typical enterprise and industrial uses will require rugged devices however. You should only choose such a device if you absolutely need it. Rugged devices will tend to be much heavier and much more costly than consumer devices. While a consulting engineer working at a highway construction site in Death Valley in August, or a utility service engineer working in Minnesota in January are likely to require rugged devices, a health inspector making the rounds to various food serving establishments will probably be just fine with a consumer device.
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provided for informational purposes only! By no means is any
information presented herein intended to substitute for the advice
provided to you by any health care or other professional or
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