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Why Are Rugged Tablets Heavier Than Consumer Tablet PCs?

Our third guest blog post is brought to you by Steve Kunert, Director of Engineering at MobileDemand.

There is that “Oh, !*?#” exclamation when a consumer tablet is dropped and shrapnel flies everywhere. Workers with rugged tablets accidently drop their tablets and simply pick them up and keep on working.

The thing most people unfamiliar with rugged tablet PC systems say when they first hold one is, “Wow! That’s heavy. Why?” The answer is pretty straightforward. The rugged tablets are designed and built to survive every day, all day, intensive use. Rugged tablets such as MobileDemand’s xTablet T1200, with an i5 processor and a 10.4” screen are full Windows 7 or Windows 8 capable devices.

rugged tablet pc cad touch screen panelLet’s start with the obviously most fragile elements of either a non-rugged consumer tablet or a commercial rugged tablet which are the touch panel and LCD display. The consumer device uses glass layers in the touch and LCD that are as thin as possible to be light weight and enable a thin sleek design for the device. The rugged tablet uses thicker glass layers to be stronger and better resist breakage from impacts and drops. The “down” side is more weight and thickness in the design.

The next major difference is in the structure of the overall enclosure of the device, the case. Consumer devices will usually have the top “picture frame” (which surrounds the glass top surface) and bottom case pieces fixed together with snap fit elements. This approach avoids the use of screws to hold the case together and again contributes to the small, sleek visual appeal of the tablet. What consumer wants to see screw heads all over the exterior of their device? Often the touch panel glass of a consumer device is the majority of the stiffness of the top case half since it is adhesively bonded to a minimally sized plastic “picture frame”.  The case halves are made of plastic, light weight pressed sheet metal or very thin wall magnesium die cast pieces.

In contrast, the rugged tablet has a top case half that has structural integrity in and of itself and the touch panel glass is often mounted with a compliant bond to the top case using foam double sided side tape. The foam tape affords cushioning to the touch panel glass so it doesn’t get exposed directly to case twists and flexures that occur when a unit is dropped. Glass, even Gorilla Glass, does not like to be twisted, it breaks!

rugged tablet pc cad case shellThe bottom case is usually die cast magnesium with thicker walls (more weight) and internal ribs (more weight) that make the back case a very structurally stiff element, resistant to twisting. Next, rather than snapping the top and bottom cases together, they are fastened with screws. There are two reasons for lots of screws. First, to attach the top and bottom together so they act as one rigid integrated enclosure and second to provide evenly distributed compression to sealing gaskets. The xTablet T1200 rugged tablet achieves its 5 foot drop capability and its IP65 water and dust sealing rating by virtue of its rigid enclosure. It even has more structure than most other tablets by adding a mid-plane magnesium stiffener between the top and base. The enclosure is held together with an abundance of screws, great for ruggedness, but a bit time consuming for service.

Since rugged tablets are used almost exclusively as business tools and not by general consumers, they are expected to have long battery life. In some cases, with the need for full work shift mobility, the units need to run from 8-12 hours on batteries alone. This need is satisfied in two ways; either build enough capacity directly into the unit with high capacity batteries (lots of cells) or make smaller batteries hot swappable and the user would be able to carry extra batteries to swap into the unit throughout the work shift. More cells in the unit achieves the desired run time but does add weight. Of course, carrying extra batteries is less than convenient. MobileDemand’s xTablet T1200 combines both approaches with two on-board hot swappable 6 cell battery packs to power its high performance i5 system. That enables the unit to run over 12 hours without a re-charge or battery swap with a typical workday duty cycle on the CPU and memory.

rugged tablet pc hot swappable batteriesRuggedness and high performance with long battery life do add some weight compared to consumer devices. For example MobileDemand’s xTablet T1200, 10.4” display device weighs in at 1.96kg without batteries, adding in two 6 cell batteries at .33kg each brings the total up to 2.62kg. 25% of the weight is batteries. MobileDemand’s xTablet T7200 is a 7” display Atom-based device and comes in at a total weight 1.41kg, 30% of that is the unit’s dual hot swappable batteries.

In summary, rugged tablets weigh more than consumer devices because each key element of the rugged device is made thicker and stronger and is fastened together more robustly. With more battery cells included in the unit, it all adds up. However, you’ll appreciate the extra weight of a rugged device when you drop it and it survives unharmed instead of becoming shrapnel!

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