With the number of different smart devices that we have come to rely on, it is hard to tell which has the best touch screen technologyt. Everywhere we turn we see ATM’s, ticket vending machines, smart phones, laptops, tablets, table monitors and kiosks and wonder which of these has the best touch screen technology. This is a question organizations, like the International Electronics Manufacturing Initiative, may be curious to know the answer to.
To make an informed comparison, we need to have a better understanding of at least the 5 most common touch screen technologies currently in use, which are: Resistive, Surface Capacitive, Projected Capacitive, SAW (Surface Acoustic Wave), and Infrared.
Resistive touch screens consist of a hard glass under layer and a soft plastic top layer with matching conductor grids. The layers are separated by a spacer and current runs thorough them. Touch creates a complete circuit at point of contact, which enables a software program to use the measurement of resistance in the circuit to determine x and y grid location. The location is then translated to an input or command. These screens have poor scratch resistance, their conductors are susceptible to breakage, and sharp input devices will puncture the top layer.
Surface capacitive screens use two rigid panels which sandwich a transparent electrode layer. When a charged input device (your finger) touches the top of the glass it steals part of the charge, enabling internal software to detect point/s of contact. Contact is then translated into inputs and commands. Though they have better image clarity than resistive screens, you have to use a charged input device (touch from a human skin), and they are sensitive to EFI/RFI.
Projected capacitive screens use a sheet of glass embedded with transparent electrode films and a chip to project a 3-dimensional electrostatic field. When this field comes into contact with a human finger, software uses the resulting change in the ratios of electrical currents to detect exact points of contact. The locations are then used to provide input and commands to the computer or smart device. These screens have excellent image clarity, are durable and accept multiple touch points. They are sensitive to EFI/RFI.
In contrast to previous technologies Infrared Touch (IR) screens use IR emitters and receivers to weave an invisible grid of light beams across a screen. When an object interrupts the beam, sensors are able to detect the touch points. These screens have the highest image clarity and are durable, though they are also expensive. It is too sensitive, so dust, dirt, snow, rain, light or even shadows may cause an accidental triggering (as if touched).
In SAW (Surface Acoustic Wave) screens, a number piezoelectric transducers and receivers are placed along the sides of the glass plate to produce a grid of ultrasonic waves on the surface of the screen. Touching would absorb a portion of the sound wave allowing the receiver transducer to pinpoint the location. However they cannot be activated using hard items, and are sensitive to solid screen contaminants and water droplets.
Which one is best? People with fat fingers should opt for screens which are not overly sensitive – that rules out SAW and IR touch screens. People who use gloves should avoid surface capacitive and projected capacitive screens. Other than that, it is mostly a matter of personal choice.