Rugged Specs Primer
A Guide to Understanding and Interpreting Rugged Computer Specs
by Tim Crews
December 2004 -- Once a very small portion of the mobile computing market, demand for industrial strength, rugged, mobile computers is growing at a rapid rate. Industrial customers are realizing that high repair and replacement costs of non-industrial strength computers, along with the decrease in productivity associated with downtime can greatly decrease profitability.
Every day, more and more vendors claim to have "ruggedized" computers. But how can you tell how rugged a terminal really is? This paper will identify the common specifications used to "describe" the ruggedness of a mobile computer, and clarify what each of these specifications truly mean. The paper will also discuss the design characteristics to look for to determine a product's true capabilities and limitations. Just because a terminal looks rugged does not mean that it is rugged.
A truly rugged industrial device is engineered, from the ground up, to operate in the most extreme hostile environments. The industrial engineering design is not only limited to the external housing, but includes internal components, special coatings, sealants, and other design features allowing computers to be exposed to extreme humidity, dust, temperatures, vibration and shock. Included in the mix is a class of products manufactured explicitly for use in hazardous or explosive environments. Understanding the differences between a truly ruggedized computer and an enhanced commercial design can be a challenging proposition for even the most informed customer.
Customers must rely on the product's specifications to evaluate the amount of ruggedization included in the product's design. However, there is not a "gold-standard" to apply to all mobile computing products. Specifications vary from product to product and market to market. To help standardize the evaluation process there are a number of ratings and standards established by various government agencies, industry organizations, and independent laboratories that allow for a better comparison of a product's industrial ruggedization.
Unfortunately, certain ratings and standards are subject to interpretation, and closer scrutiny of a vendor's claims is often warranted. In certain circumstances it may be important to obtain detailed testing information from the manufacturer to verify the product's ability to operate in certain environments. Understanding an industrial computer's ruggedization specifications can be the most important information when purchasing a ruggedized device. Not understanding these specifications can lead to improper evaluation of a product's performance, and result in a bad purchasing decision that can cost an organization greatly in the long run.
Common Specifications For Ruggedized Mobile Computers
Listed below are some of the more common ratings and standards frequently used by manufacturers to define a product's degree of ruggedization.
IP (Ingress Protection) ratings are standards for electrical enclosures. The rating refers to the equipment's ability to permit solids and liquids to penetrate the computer's enclosure. The protection standards are defined by the IEC (International Electrotechnical Commission). A mobile computer's IP Rating is expressed as a two-digit number (Example: IP-66). The first number designates protection from solids, while the second number designates protection from liquids. Please refer to the table below for specific IP rating information.
If a device is truly ruggedized for use in an industrial environment, then an IP rating will be specified. If a computer is being used in an environment where dust and moisture are prevalent, then the IP rating must be considered. If the IP rating is not specified, then you can assume a computer will not be resistant to dust and moisture. Any computer product being used in a truly industrial environment should have an IP rating of IP-65 in order to be fully protected from dust and liquids. Dust and moisture can cause major problems to internal computer components. Even if a device is not used in an industrial environment, it can become exposed to levels of dust and moisture that can eventually cause major problems.
It is important that manufacturers have their equipment certified by an outside laboratory to verify the product's IP rating. UL and CENELEC are two such laboratories, but many different laboratories exist that provide this service. The important thing is that the product is certified by an outside organization. If IP ratings are specified on a product's data sheet, then an approval certification number should also be included (Example: EN 60 529 or Approved to IEC 529).
Another important consideration is that every configuration of the product is IP certified, and not only one specific configuration. Many manufacturers will claim a certain IP rating, but this rating is only achieved with one specific, and usually expensive configuration. All available configurations should be IP rated for proper protection to allow the customer flexibility when ordering a mobile computer.
NEMA (National Electrical Manufacturer Association)
NEMA ratings are standards that are useful in defining the types of environments in which an electrical enclosure can be used. The NEMA rating system is defined by the National Electrical Manufacturer Association, and frequently signifies a fixed enclosure's ability to withstand certain environmental conditions. Please refer to the table below for specific NEMA type designations.
NEMA ratings are rarely applied to mobile devices, and are mainly applied to fixed enclosures. For example, a NEMA rating would be applied to a fixed electrical box mounted outside, or a fixed enclosure used to house a wireless access point. Most enclosures rated for use in an outside environment include a NEMA 4 rating. NEMA ratings have more stringent testing requirements to verify protection from external ice, corrosive materials, oil immersion, dust, water, etc. These stringent testing requirements can rarely be applied to mobile devices, but there is a correlation between NEMA ratings and IP ratings. However, this correlation is limited to dust and water. The "Comparison Table" below provides a comparison between NEMA ratings and IP ratings. It is important to realize that this comparison is only related to the protection provided against dust and moisture. For this reason, this table can only be used to convert NEMA ratings to IP ratings, but not vice versa. A few manufacturers of mobile computers will include NEMA ratings in their specifications, and it is important to understand how the NEMA specification correlates to a product's IP Rating.
MIL-STD (Military Standard) or MIL-SPEC (Military Specification)
The MIL-STD specification is a series of guidelines established by the U.S. Department of Defense in order to define specific performance and manufacturing requirements for all types of equipment. In most cases, products must be designed in accordance with the MIL-STD to be considered acceptable for use by the U.S. Department of Defense. A product's MIL-STD compliance is also a consideration for many state and local governments when purchasing mobile computers for use in public safety, emergency services, maintenance, etc. The MIL-STD 810F standard was released on January 1, 2000 (superseded MIL-STD 810E). MIL STD 810F includes testing protocols to simulate environmental stresses from rain, humidity, salt fog, sand/dust, vibration, shock, temperature, etc. A copy of MIL-STD 810F can be downloaded from the United States Army Developmental Test Command at http://www.dtc.army.mil/ pdf/810.pdf.
The MIL-STD 810F standard is an all-encompassing standard that is frequently used for ruggedization testing by mobile computer manufacturers. Many manufacturers and laboratories will design their ruggedization testing in accordance to the MIL-STD 810F guidelines. However, it is important to note that when the MIL-STD 810(x) specification is listed on a product's data sheet, this usually only applies to the vibration and shock component of the standard, and does not mean that protection is included from salt fog, corrosion, rain, humidity, temperature, etc. Therefore, IP Ratings are frequently used to signify protection from liquids and solids, and the MIL-STD is used to specify protection from shock and vibration. Since MIL-STD 810(x) includes many different tests, the manufacturer must state which section of the standard they are using. For example, section 514.5C-3 of MIL-STD 810(x) includes vibration and shock testing parameters.
Also, it is important to pay close attention when manufacturers claim MIL-STD 810F, because vibration and shock testing can be performed on non-operating units, and the units are turned on after the test. The units must be tested while in operation to achieve an accurate performance rating. Also, many manufacturers will include actual testing parameters on specification sheets (Example: 40g Shock, 28g Peak Vibration), rather than claim MIL-STD 810F. This could signify that the testing used does not meet MIL-STD 810F requirements.
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.
Another important aspect to consider is the testing procedures used to verify a product's drop specification. A product should be dropped on all sides to verify its ability to withstand shock from any direction. For example, a computer's display can be very sensitive to the shock associated with a drop. The drop test should include all sides to verify that the display, and other sensitive components will withstand the shock and operate properly. It is important to pay close attention to the details included with the drop specification, because many manufacturers will claim 6-foot drops to a "hard surface". This can be misleading, because the term "hard surface" is open for interpretation. Concrete is usually the standard surface used for proper testing, and the drop specification should be questioned if this is not clearly stated. It is also important to verify that the standard product meets the drop specification and that a separate protective accessory is not required (i.e. case, rubber boot, etc).
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.
Intrinsically Safe Specifications
Many ultra ruggedized mobile computers will include intrinsically safe (I-Safe) specifications or approval ratings. Understanding I-Safe approval ratings can be a difficult proposition for even the most informed customer. 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.
Each designated hazardous environment has specific certification requirements for all equipment used in the I-Safe area. Intrinsically safe equipment must carry a label, which specifies the exact I-Safe rating for the equipment and the name of the NRTL (Nationally Recognized Testing Laboratory) who tested it. Testing laboratories have very stringent certification requirements that vary according to the level of I-Safe approval desired. Therefore, each intrinsically safe device is certified for different levels of I-Safe approval, and can only be used in specific hazardous environments. The bottom line is that close attention must be given to the specific I-Safe approval certification for each individual piece of equipment. Just because a device has an I-Safe rating, does not mean that the device can be used in any I-Safe area.
I-Safe approval certifications are made up of multiple classes, groups and divisions that correspond to the specific hazardous environment a device is approved to operate in. Each class consists of two divisions and certain classes have multiple groups. For example, Class I includes flammable gases, Class II includes flammable dust, and Class III includes flammable fibers. Each class has two divisions. Division 1 includes environments where explosive material is present in the air at all times. Division 2 includes environments where explosive material is stored in sealed containers, and explosive material is only present for short time intervals (when a failure occurs or during maintenance). Also, Classes I and II are broken down into groups that correspond to the explosive properties of each specific material. For example, Group A includes Acetylene and Group E includes aluminum dust. In addition, I-Safe approval ratings differ significantly from country to country. A device that is I-Safe certified for use in the U.S. may not be certified in Europe. Needless to say, understanding the differences between I-Safe approval certifications can be a full time job, and can make the purchasing decision for an I-Safe device a very difficult and lengthy process. However, to ensure the safety of your facility and personnel this verification process is extremely important, and cannot be overlooked. In order to create a "gold standard" for I-Safe products, in June 2003, I-Safe equipment will require ATEX certification. This certification standardizes I-Safe approval ratings and will be used in the U.S. and Europe. This should help make understanding I-Safe approval ratings much easier.
To truly understand a computer's "ruggedness", you need to not only understand ruggedness specification definitions, but also how a vendor determined a particular product's specifications. The initial cost of a truly industrial rugged terminal may be more than the cost of a non-industrial terminal, but long-term it's more than worth it due to significant savings on both repair and replacement costs, and the increase in productivity associated with the units remaining on the job.
Tim Crews is a product manager for LXE, a company committed to providing rugged and reliable mobile computing and award winning customer support. If you ever have any questions on ruggedness, please feel free to contact Tim at LXE either by e-mail at firstname.lastname@example.org or by phone at 1-800-664-4593.