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Capacitive Vs. Resistive Touchscreens

A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area.  Although this technology was invented in the UK in 1965 it only gathered commercial pace with the spread of computers in the 80s and has witnessed the greatest boost in momentum in recent years from the mobile phone sector.

There are almost a dozen different technologies for touchscreens but by far the 2 most common are resistive and capacitive.

Resistive touch screens respond to pressure and have been perhaps the most common implementation of touch screen technology due to its low cost.  A resistive touchscreen panel is made up of electrically conductive layers. When the panel is touched the layers come into contact at that point which can be accurately detected and sent to the controller for processing.  Because the touch is sensitive to applied pressure the touch source can be any object, either a human finger (including gloved) or any other inanimate pointer.  One disadvantage however of resistive technology is its vulnerability of being damaged by sharp objects.  Although uncommon and unknown by many resistive touch screens can and do support multi-touch.  Although multi-touch is rarely a useful feature for most business processes, if required it does not limit your choice of technology.  In fact we have devices that support 4 independent touch points on a resistive screen.

Capacitive touch screens involve an insulating outer layer (normally glass) coated with a transparent conductive metal compound.  The technology works by detecting changes in electrical conductivity across that layer.  As the human body is also an electrical conductor, touching the surface of the screen results in interference of the screen’s electrostatic field, the location of which can be detected and sent to the controller for processing. Because the technology relies upon electrical interference from a conductive source capacitive touchscreens do not work through most gloves as they are electrically insulating.  Likewise an ordinary stylus or other object cannot be used. Yes it has rapidly become the common touch screen technology found in virtually all touchscreen consumer mobile devices today.  Capacitive screens have become loved for use of ‘gestures’ and ‘multi-touch’.  Whilst neither is exclusive to this type of screen it could be fairly said that these motions are easier and a little more natural when less pressure need be applied.  However, we rarely encounter a use for these types of touch-motions under business conditions.

Choosing the right touchscreen technology for your business project

When considering the most suitable technology for your business device it’s important therefore to know how the device will be interacted with by its users.  As always with computers it’s the software that guides the hardware choices.  As we are all consumers ourselves it’s easy to assume that the technology we carry in your pocket by way of our mobile phones is the right technology for all devices utilizing similar technology concepts.  This can only be the case by luck – a business device demands its proposed functions be means tested against available technology options without preconceptions and biases.

The key questions to ask when selecting the right touchscreen technology are:

  1. Who will use the tablet – Will the tablet have a single owner/operator or will the device be used by many people/the public?
  2. How will the tablet be used – Will the interaction be with a finger or stylus? Will gloves be worn?
  3. Where will the tablet be used – What are the environments the tablet will be used in?
  4. What is the function of the tablet – What interaction is necessary?  How much accuracy is required?  Will specialised tasks be performed such as drawing or signature capture?

Who will use the tablet?

Knowing the user type can give an early indication of preferred screen type.  Perhaps because the type of user already has a distinct and previously evaluated preference for a particular screen type.  Sometimes something as simple as this can be overlooked by those responsible for procuring a device.  Also determining and understanding the user as a start point should prevent us from making the wrong choice as we consider other factors.  Ultimately everything we consider later must again be tested against ‘Who’ – is a perceived benefit still a benefit for the user.  For example if the users’ of a device will vary such as with the general public then we must keep in mind that we cannot expect the user to familiarise themselves with any advanced method of use that a single carrier-user may benefit from.

How will the tablet be used?

Knowing ‘how’ will typically be the decider for most businesses.  If you have key criteria in the ‘how’ then making the wrong decision here could effectively make the resulting decision completely ineffective.  What you must know is that if you (a) wish to use a stylus, or, (b) the user will be wearing gloves, then you will require a resistive screen.  There are workarounds with capacitive screens but the reality is that they are poor solutions.  Capacitive pens are either blotter-style only, or very inaccurate and with varying efficiency in contact.

Where will the tablet be used?

Environment can make a difference, particularly if that environment is hazardous.  If the screen is not inherently IP protected and any sort of transparent cover is placed over the screen (for example as part of a protective case) then you will require a resistive screen.  Pressure can easily transfer through various layers, but the electrical interference of your finger necessary to interact with capacitive screens is easily impeded.  For example some screen protectors, especially higher quality ones with transflective qualities will interrupt the mechanism that capacitive screens rely upon and the two are therefore not compatible.

What is the function of the tablet?

In some ways the most important question is regarding the function of the tablet.  Business use of technology is always different from consumer usage and therefore it’s important to identify exactly what the tablet will be used for and specifically what the user must do to achieve it.  These are questions you must ask and answer frequently testing against the previous questions.  If you application requires accuracy, touching small areas/objects/button and/or signature capture/drawing/other operations that require natural pen movement then the obvious technology choice is a resistive screen.

Summary

Although the consumer market has exhibited a trend of capacitive screen mobile devices, resistive screen technology remains very much in use and is frequently preferred by business users.  Where capacitive touchscreens suffer is with accuracy.  This may be unnoticeable ‘all-thumbs’ friendly apps of the modern smartphone which centre around swiping gestures and for zooming in and out of web pages.  But these consumer orientated functions rarely matter to businesses that would prefer greater accuracy.  To quantify this, technically speaking resistive is 3-4 more accurate than capacitive due to the sensor spacing.  With a capacitive screen you cannot achieve a fine-tip contact such as you would expect from a pen.  This is why capacitive styli are typically 5mm or so in diameter and in many cases like a bingo blotter.  If your application is straight forward button activation then this may not present an issue but for most uses, especially signature capture and any interface akin to the controls common within the Windows GUI then resistive is a more comfortable choice.

Where businesses do not have a specific requirement for resistive screen touch technology, capacitive screens provide a solution that offers both a familiar interface for users and an easily accessible means of interfacing with simple finger control.

Other technologies to consider

Other technologies do exist although their implementation is not as common.

Infrared touchscreens use an array of infrared LED emitters with respective photo detectors around the perimeter of the screen.  Essentially the screen is surrounded with horizontal and vertical beams enabling the sensors to accurately detect the location of touch.  A major benefit is that it can detect any input and because the sensors surround rather then fill the screen the longevity and durability is very high.  Of course the optical clarity of the screen is also greater because no sensor layer or conductive layer lies between the user and the actual display element.  Infrared touchscreens are generally used in outdoor applications, point-of-sale and other environments where multiple occasional users are involved, or anywhere where the pros of the technology offer a significant advantage.

Active digitizers are an input method most commonly associated with an input tablet and pen pair.  The ‘tablet’ in this description is simply that and does not embody a visual display; rather it is a flat surface on which to use the connected pen.  Classical use was for digital artists to have an input method most akin to using a pen or brush.  However this input method can be used in conjunction with a display surface so that the pen input is directly on top of and interacting with the display elements below.  This is usually implemented as a dual input when both an active digitizer and either resistive or capacitive technology is used in tandem.  This is so that you can still use the touch screen without the special pen paired to the digitizer.

The main advantage to the active digitizer solution is that palm rejection is inherent.  E.g. if your palm touches the screen whilst using the pen, the palm is not interpreted as a touch point, as only the pen is being recognized.  However active digitizers are usually integrated into only high end devices making this technology combination currently beyond the lower and mid-range sector.

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