Tablet computers, also known simply as tablets, are notebook-sized mobile computers - equipped with touchscreens - which are typically used wirelessly. Common models include Apple's iPad Air 2, Google's Pixel C, Samsung's Galaxy Tab S2, Microsoft's Surface, and Amazon's Kindle Fire. 

Features

A tablet computer falls somewhere between a smartphone and a laptop computer in size and functionality yet it incorporates some features of both of those types of devices.

Portability is one of the main reasons for selecting a tablet computer over another type of device. Tablet computers are smaller, thinner, and more lightweight than laptop computers. The screen size is larger than that of a smartphone, making it easier to read and navigate the touchscreen.

Connectivity is another key feature. Like a smartphone, a tablet computer is designed to operate wirelessly, either over a Wi-Fi network or via a 3G or 4G cell phone network.

Compatibility is another feature of a tablet computer. Many tablets share operating systems (OS) with smartphones or computers, making it relatively easy to sync data back and forth.

Applications

Many tablets are designed for consumer use. These and other specialized tablets can also be used for industrial and military applications. It is important to know the intended of application of the tablet before making a purchase because the use will dictate specification requirements.

Some applications of tablet computers include:

• Personal use
• Research
• Construction
• Manufacturing
• Transportation and logistics
• Forestry
• Utilities
• Emergency personnel
• Healthcare and medical
• Military 

Types

Tablet computers are available in different configurations. One may be simply a tablet, while another has an attached keyboard or is designed to operate in extreme conditions.

Tablet configurations: slate, convertible, booklet, and rugged.

Image Credits: Apple | Lenovo | blogcdn.com | Mobileworxs

Slate

A slate is a traditional standalone tablet, for example, an Apple iPad or Samsung Galaxy Tab. Depending on the tablet it may be possible to connect a keyboard via Bluetooth. Slates are used for consumer activity and occasionally in professional and industrial applications. Slates may come in regular or mini sizes.

Convertible

A convertible tablet has an attached full keyboard. The keyboard can be folded behind the screen so the device can be held as a tablet. It can also lie in front of the screen like a laptop computer.

Booklet

Booklet-style tablet computers have two screens. The device opens like a book with a screen on each side. They aid in multi-tasking and may accommodate handwriting recognition.

Rugged

Rugged tablets are designed for use in environments where less durable tablets would break or fail to operate. According to MobileDemand, a standard tablet that "spends more than 40% of its time outside of the office" has an annual failure rate of "more than 30% per device." Failure rates for rugged tablets in similar conditions are less than 4% per year.

They are durable and shockproof to withstand research, military, construction, or other outdoor work. Tablets specifically geared toward children offer rugged features. Some conditions that rugged tablets are built to withstand include:

• Extremely high or low temperatures
• Vibration
• Dusty conditions
• Direct sunlight
• Wet conditions
• Drops onto hard surfaces 

Specifications

Operating System

A number of operating systems (OS) are available for tablet computers and they can be specific to a device by a certain manufacturer. For example, iPads are manufactured by Apple and will carry that company's OS, called iOS. Google's Android platform is available on models by multiple manufacturers.

Software designed for use on personal computers, such as Microsoft Excel or Matlab, cannot be installed on most tablet computers. Apps, or applications, are small programs used on tablet computers and other devices. Each OS is compatible with certain apps. Examples of apps include calculators or versions of existing programs like Microsoft Excel. Some apps are free and others require a purchase to download.

Below is a comparison of some of the operating systems available for tablet computers as of February 2016 (source: netmarketshare.com). The market share percentages do not total 100% because of lesser-used systems that were not included.

Size

Sizing for tablet computers is typically broken down into two categories:  6 to 8 inch tablets and 9 to 13 inch tablets. Smaller models weigh less and may lack certain features such as cameras. Selecting a tablet computer size should be based on the desired application and whether compactness or a larger functional screen size is more important.

Processor

Processors vary by manufacturer. Apple, for instance, has its own processors; other manufacturers may use Intel or ARM processors. The table below describes some processors that are commonly used in tablet computers.

Storage

Because tablet computers are meant to be used wirelessly, data to be accessed is stored on the device itself or possibly in cloud storage. While some devices have a slot for a micro SD card to expand memory, in most cases there is no connection to other storage devices such as USB drives or portable hard drives. The memory on the device will determine how much media like photos, music, video, or other large files can be stored.

Internal memory cannot be expanded at a later time and can range from 1GB to 500GB, although 8GB - 64GB are the most common sizes for consumer tablet computers.

Battery

The battery life of a tablet computer depends on a number of factors. Battery life can be influenced by:

• Battery size
• Screen backlight brightness
• Operating system efficiency
• Sleep mode vs. powering down the tablet
• App usage
• Browsing the web
• Streaming video

Many tablets advertise 6 to 11 hours of battery life.

Screen Type

Tablet computers have touchscreens, eliminating the need for a keyboard or mouse, although those devices can be added. Actions such as tapping, swiping, and turning the device can produce different results. A stylus, or rubber-tipped pen, can be used instead of a finger to press a button or write on the screen.

• Capacitive touchscreens are used on most tablets. These screens respond to skin touch rather than pressure and have less accuracy for handwriting unless used with specialized apps. The capacitive touchscreen allows additional actions such as swiping, pinching, and expanding items on the screen. The screen has a solid outer layer, such as glass, with electrostatic sensors beneath it.
• Resistive touchscreens are used in point-of-sale (POS) electronic signature pads used in retail stores and by delivery services. They intended for use with a stylus but can also respond to finger or fingernail pressure. Precision is required for accurate sensing and action. These screens have multiple layers with the outer layer made of a slightly flexible material.
• Active screens are used on devices with screens that do not respond to the touch of a finger. A special stylus must be used with these screens, which are the best type to translate handwriting or drawing to a screen.

A rugged tablet computer that will be used in extreme conditions may have other screen features. The screen may be scratch-resistant, reduce glare when viewed in direct sunlight, and be able to deal with extreme temperature ranges.

Screen Resolution

The display resolution of a screen is the number of pixels in each dimension that can be displayed. It is shown as width by height, so an iPad with a resolution of 1024 x 768 is described as being held lengthwise.

Screen resolution for tablet computers ranges from 1024 x 600 to 2560 x 1600. While higher numbers generally indicate a clearer picture, at some point the numbers may exceed the resolution of the image file or the quality of a video.

Pixel Density

Pixel density, also known as pixels per inch (PPI) or dots per inch (DPI), is a measurement of the number of pixels horizontally and vertically in a square inch of space. PPI in tablet computers can range from about 130 PPI to more than 400 PPI.

Apple's Retina display, at 264 PPI (326 PPI on the iPhone 4 and later models), is available in the iPad 3, iPad 4, and iPad Air. Retina is an LCD (liquid crystal display) with a high enough pixel density that the human eye will not notice pixilation at a normal viewing distance. It is unlikely that the human eye can detect an improvement in quality at a higher PPI unless a microscope is used for viewing.

Accelerometer

An accelerometer may be used in a device that responds to being turned, tilted, or shaken. Turning a tablet computer to a vertical or horizontal orientation will change the corresponding screen orientation to portrait or landscape. Tilting or shaking a device may trigger a response from an app like a game.

Navigation is another application of an accelerometer and may be useful in apps related to mapping and changes in elevation or distance. The accelerometer may also provide image stabilization for a built-in camera.

Camera

Tablet computers may have cameras on the front or back of the device or in both locations. A rear- or back-facing camera is located on the opposite side from the screen and may be used for taking photos or videos, >communication, and teleconferencing. A front-facing camera is located on the same side of the device as the screen (facing the user) and can be used for taking pictures or videos while observing a mirror image on the screen.

Cameras vary in terms of megapixels, autofocus, flash, and incorporated microphones.

Internet Connection

Tablet computers can connect to the Internet via a Wi-Fi network or cell phone network; some can connect both ways.

A tablet that can connect only via Wi-Fi is limited to areas with these networks. A tablet that connects via a 3G or 4G cell phone network may be subject to a contract or month-to-month billing with a cell phone carrier. The added cost may be worth it for those who work in the field or in areas that do not have reliable Wi-Fi networks.

Rugged tablet computers have better reliability when it comes to wireless connectivity. Multiple radios may be used in the product to reduce productivity loss in the event of disconnection.

Inputs, Outputs, and Accessories

While connection ports and buttons vary between tablet manufacturers, most devices come with the following:

• On/off button
• Power connector
• 3.5 mm headphone jack
• Speaker
• Volume controls and mute switch

Tablet computers may also include:

• microSD card slot
• USB port
• Docking port
• HDMI out

Apple products do not offer the ports listed in the second group above, but there are many adapters produced by Apple and by third party manufacturers.

Many tablet computers feature Bluetooth connectivity. Keyboards and other accessory devices can be connected and synced to the tablet. Some tablet computers, such as the Microsoft Surface, are designed to look and feel like laptop computers via the attachment of special keyboards and other accessories.

A number of cases are available for tablet computers. Some protect the back or screen and others protect the whole device. Cases that extend battery life, waken the device on opening, or that have attached keyboards are available.

Materials

Tablet computers may be made of metal, glass, plastic, or some combination of those materials. Many Android models have plastic bodies while Apple iPads have aluminum bodies. There are several factors to consider when choosing a tablet computer based on its outer material:

• Durability - Plastic scratches more easily but scratches on metal will be more noticeable. Plastic may have slightly more give when a device is dropped.
• Heat - Metal may be hot to the touch while plastic may stay cooler longer.

Tablet computer screens may be constructed from glass or plastic.

Rugged tablet computers are constructed to be durable through extreme environmental conditions and even when dropped. An antimicrobial finish is an option with some manufacturers.

Rugged tablet testing.

Video Credit: MobileDemand Rugged Tablet PCs via YouTube

Security

Tablets offer features for data security and protection against viruses and theft. These features may be physically built into the tablet itself or available as add-on applications. Some features that may be available on a tablet include:

• Password or PIN code
• Fingerprint reader
• Virtual private network (VPN) connectivity
• Encryption
• Device location
• Remote data freezing and deletion
• Anti-virus 

Tablet Comparison Guides

The number of available tablet computer options has grown in recent years. Making a choice may still be difficult even after narrowing down the desired application, type, and specifications. It can be useful to compare options side-by-side when conducting research to choose a tablet.

The following comparison guides are broken into three groups: small tablets, large tablets, and rugged tablets. There are many more tablets available on the market than are listed in this guide, but the guide provides a starting point to learning about some of the top tablets on the market. This data is current as of June 6, 2016.

Small Tablets (7" to 8")

Teardown analysis of similar products:

• Apple iPad Mini A1432 (16GB, Wi-Fi only)
• Samsung Galaxy Tab 7.7 SCH-i815 (Verizon - LTE) + GT-P6800 (Wi-Fi + 3G)
• Amazon Kindle Fire D01400

Standard Tablets (9" to 13")

Teardown analysis of similar products:

• Apple iPad Air
• Samsung Galaxy Tab 10.1-inch LTE
• Google Pixel C (C1502W)
• Microsoft Surface Pro (9SR-00001)

Rugged Tablets

Standards

Tablet computers designed for use in rugged environments have their own sets of standards:

IEEE 1156.1-1993 — Microcomputer environmental specification for computer modules.

EN50155 — Railway applications — electronic equipment used on rolling stock.

MIL-STD-810 — Environmental engineering conditions and laboratory tests.

References

Operating Systems Market Share

8 Essential Features Every Tablet Buyer Should Look For

Everything You Need to Know About Touchscreen Tablets

Image credits:

Xplore Technologies (rugged tablet) | tabletnews.com (screen resolution) | Vizio (port diagram)