What kind of touch screen technology should we use?
A touch screen uses XY co-ordinates to locate the touch. It emulates a mouse click at that point. Here’s a quick guide to the main types.
Resistive
Resistive screens incorporate two electrically conductive layers separated by air. When a finger or stylus presses the screen, it compresses the layers together and changes the electrical current, which the screen recognizes as a touch. Resistive touchscreens work well with fingertip input and support multi-touch applications. Their cost is relatively low when compared with other technologies but very cheap models will have a limited life.
Surface Acoustic Wave (SAW)
SAW technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to a controller for processing. SAW touch screens tend to be more expensive than resistive but are very durable. If they are well-looked after, they will stand heavy use for years. However, contaminants on the surface or around the edge of the screen can interfere with their functionality. This can be avoided by regular cleaning.
Capacitive
Capacitive touch relies on the human body's electrical properties. In a basic configuration, a capacitive screen is given a uniform electric field by electrodes placed around its edges, so that a finger touch draws current from each corner of the screen. The controller then measures the current flow from the corners to instantly calculate the finger’s location. This option is durable but has limited resolution. It is prone to false signals and needs calibration during manufacture. It is therefore most often used in simple applications such as industrial controls and informational kiosks.
Projected Capacitive Touch (PCT)
This version of capacitive technology permits more accurate and flexible operation, by etching a conductive layer. An XY array is formed either by etching a single layer to form a grid pattern of electrodes, or by etching two separate, perpendicular layers of conductive material. Applying voltage to the array creates a grid of capacitors. Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field. The capacitance change at every individual point on the grid can be measured to accurately determine the touch location. The use of a grid permits a higher resolution than resistive technology. This makes multi-touch operation possible and it also allows operation without direct contact - so that the conducting layers can be coated with further protective insulating layers and operate under screen protectors or behind glass. PCT is used in a wide range of applications including POS systems, smartphones, as well as kiosks. Perhaps the most notable example of a consumer devices using PCT is the iPhone.
NeoProducts has experience with all these technologies, and can advise you on the most cost effective solution for your particular application and budget.
SAW technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to a controller for processing. SAW touch screens tend to be more expensive than resistive but are very durable. If they are well-looked after, they will stand heavy use for years. However, contaminants on the surface or around the edge of the screen can interfere with their functionality. This can be avoided by regular cleaning.
Capacitive
Capacitive touch relies on the human body's electrical properties. In a basic configuration, a capacitive screen is given a uniform electric field by electrodes placed around its edges, so that a finger touch draws current from each corner of the screen. The controller then measures the current flow from the corners to instantly calculate the finger’s location. This option is durable but has limited resolution. It is prone to false signals and needs calibration during manufacture. It is therefore most often used in simple applications such as industrial controls and informational kiosks.
Projected Capacitive Touch (PCT)
This version of capacitive technology permits more accurate and flexible operation, by etching a conductive layer. An XY array is formed either by etching a single layer to form a grid pattern of electrodes, or by etching two separate, perpendicular layers of conductive material. Applying voltage to the array creates a grid of capacitors. Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field. The capacitance change at every individual point on the grid can be measured to accurately determine the touch location. The use of a grid permits a higher resolution than resistive technology. This makes multi-touch operation possible and it also allows operation without direct contact - so that the conducting layers can be coated with further protective insulating layers and operate under screen protectors or behind glass. PCT is used in a wide range of applications including POS systems, smartphones, as well as kiosks. Perhaps the most notable example of a consumer devices using PCT is the iPhone.
NeoProducts has experience with all these technologies, and can advise you on the most cost effective solution for your particular application and budget.
Products Group 2010