Touch sensors are now standard in most wearables and IoT products. They are used in a wide range of display applications, from smart homes and appliances to security and industrial solutions. There are two common types of touch sensors: capacitive touch sensors and resistive touch sensors. Here’s how they work.
Touch Sensors
Touch sensors are increasingly used on displays. This has become the norm, especially when it comes to smartphones and tablets. There are two common types of touch sensors/screens: capacitive and resistive.
How Capacitive Touch Sensors Work
It’s called capacitive because the technology is based on capacitive coupling that detects anything that is conductive or has a dielectric different from air. In this case, the human body (your fingers) is being used as an electrical charge conductor.
The way it locates where your finger is on the screen is the change of local electrostatic field when your finger touches the glass of the capacitive surface. An image processing controller continuously monitors the electrostatic field (or the movement of each tiny capacitor) to find where exactly the finger touched the screen. Figure 1 shows a helpful diagram from TCI.ed on how it tracks the electrostatic field.
Figure 1: How the image processing controller evaluates touchpoints. (Source: TCI.de)
The advantages of using capacitive touchscreens include a brighter and sharper image due to the glass layer, highly touch sensitive, and supportive of multi-touch functions. This makes it great for smartphones and why you see it on iPhones, Samsung Galaxy, and HTC phones. Some disadvantages on using this touchscreen over a resistive one is that it is dependent on the conductivity of the human body, so a person can’t wear gloves (unless it has a conductive material on it). It’s also more expensive, and glass is prone to breaking more often.
Ähnliches Produkt:
Ähnliches Produkt:
How Resistive Touch Sensors Work
The other type of touch screen/sensor is resistive. Unlike capacitive touch sensors which have a glass layer only, resistive touch sensors have several layers, where the two main layers are the flexible plastic and glass layer. The front surface has a flexible scratch-resistant plastic with a coating of conductive material (usually Indium Tin Oxide) on the underside. The second layer is also coated with ITO and is made of either glass or hard plastic. When a finger (or a stylus) presses down on the flexible plastic, it contacts the second layer and measures the resistance of both the layers at wherever the point of contact was. Figure 2 shows a diagram on how it works.
Figure 2: Resistive touchscreen and its layers. (Source: Epec Engineered Technologies)
Advantages compared to capacitive include: it can be used with finger, gloves, and stylus, high resistance to dust and water, and low production costs. Disadvantages are that it is not as sensitive – requires more pressure on the screen, has poor contrast due to additional reflection from the extra layer of material placed over the screen, and does not support multi-touch.
Ähnliches Produkt:
If you liked this article, check these articles out:
See how Motion Sensors work!
Learn how Fingerprint Sensors scan your fingerprints.
See the inner works of Uninterruptible Power Supplies (UPS) and if you need one.