PCAP vs Resistive Touch

When selecting touch screens for heavy-duty industrial applications it can be difficult to find solutions that are compatible with gloves and harsh industrial environments. As you may know there are two different kinds of touch sensors, capacitive and resistive. For many years resistive touch technology has been the top choice for most touchscreen controls found on industrial machinery. Historically, one of the major advantages of a resistive touch screen was the ability to use anything on the screen, finger, stylus, and gloved finger because resistive touch screens are based on pressure, so anything can be used to close the gap and actuate the sensor.

When first introduced to the market, Projective Capacitive (PCAP) improved optical clarity and was scratch resistant but did not perform well with gloved hands. However, new advancements in PCAP are changing that and making it a viable solution for industrial applications. This now gives product engineers two options to choose from either sticking with the historically more common application or moving forward with recent improvements in PCAP technology. With the new and improved (PCAP) technology we will explain how and why the new PCAP technology is replacing resistive as the go-to for industrial applications.

Resistive Touch Technology

Resistive touch screens had been the focal point on the factory floor room operations for decades. This technology features two transparent layers separated by a thin gap with spacers. When you tap the surface of a resistive touchscreen, the two layers press each other which triggers a voltage to pass through and identify exactly where you touched. This technology works thanks to pressure, and is known for its capability to identify a touch with a finger or an object. Furthermore, the surface of the touch sensor is invulnerable to foreign objects such as dust and water drops. Another major advantage resistive touch screens have had is its cost effectiveness but nevertheless, resistive touch includes several disadvantages as well. 

Disadvantages of Resistive Touch Screens:

          1.) Multi-touch is not supported (pinch, zoom, etc.)

          2.) Not every sensitive, more pressure is need to actuate the sensor (however, this can be advantage                     for some applications)

          3.) Lacks optical clarity

          4.) Extra layers of material over the display dull the contrast

          5.) More prone to scratches 

          6.) Heavy use can breakdown the sensor leaving it unresponsive. If the surface is damaged, the sensor                     will stop working

          7.) Extra layers of material over the display dull the contrast 

          8.) Not available beyond 24”size due to economic scale 

Projected Capacitive (PCAP) Touch Technology

Capacitive sensing in touch screens has been around since the 1970’s, but with the recent explosion in popularity of the smartphone, projected capacitive sensors (PCAP) have come to the forefront of touch screen technology. As a result of the success of advanced smartphones, users have discovered the many benefits of projected capacitive touch panels. Users are realizing the gesturing interface used on the advanced smartphone is a natural way of interacting with electronic devices. Now that projected capacitive touch panels are available in larger panel sizes, designers can bring this same experience to a variety of embedded systems where durability, reliability and overall performance of this technology can add value to more industries than just consumer products. 

PCT technology is a capacitive technology which permits more accurate and flexible operation, projection of the touch field through additional layers of material plus full multi touch capability. Typical construction of a PCT technology sensor allows for operation without direct contact to the touch sensor. Thus the touch sensor can be located behind further insulating layers, and operate even under screen protectors, or behind weather and vandal-proof glass. Due to the top layer of a PCT being glass, PCT is a more robust solution versus resistive touch technology. Since PCT being glass, PCT is a more robust solution versus resistive touch technology. Since PCT technology construction is an X and Y matrix of capacitors capable of locating multiple distinct touch points, PCAP sensors are true multi touch capable. 

With the recent improvements of PCAP technology it quickly won over industrial application market shares from resistive touch. PCAP touch screens started to be introduced more in applications where customers require a more rugged surface due to susceptibility to scratches and mishandlings making it the new best solution for industrial applications. 

Advantages of PCAP Touch Screens:

          1.) More scratch/abrasion resistance due to a glass or acrylic lens

          2.) High responsive, touch sensitive- the actuation of a capacitive sensor is light touch and smooth                         when it comes to drag and swipes

          3.) Multi-touch is supported

          4.) Sensor will continue to work even if the top lens is cracked/broken. PCAP is great for heavy use                         applications

          5.) High contrast, great visual appearance 

Why PCAP for Industrial Applications

Capacitive touch screens were actually invented almost 10 years before the first resistive touchscreen. In the beginning PCAP were typically used more for consumer products like laptops, smartphones and tablets. Here we discuss some features that allow the new technology to overcome the past and now be the lead touchscreen for industrial applications.

1. 1.) Touch Controller

          There are two options for incorporating touch controllers in the PCAP touch devices. In the first one, an             Integrated Circuit (IC) controller is mounted on the surface on a separate PC board, known as Chip on               Board (COB), which allows signals to be transmitted from the touch sensor through the flexible                         printed circuit to the PCB. Then, the IC firmware will transform the capacitance data into a digital                       touch position data which will be sent to the host computer.

           The second option is to mount the controller IC chip on the surface directly on the touch flex tail, also               known as Chip on Flex (COF). In this case, an analog capacitance signal is converted into digital                           position data on the FPC which will be sent to the computer via serial interface.

2. 2.) Noise Immunity

           Electromagnetic interference (EMI) noise can interfere with the accurate detection of touch events in               PCAP touch screens. To maintain the accuracy of the touch detection, the PCAP touch controller                       leverages firmware and hardware to avoid noise interference at different frequency bandwidths.

3. 3.) Water Handling

           On certain industrial applications, water can accumulate on top of PCAP touch screens and trigger                     false touches. To avoid those false touches, the latest PCAP technology features water repellent                       surface treatments and a firmware algorithm to differentiate an actual touch from water droplets.                     These new features enable the touch screens to work flawlessly with challenging operating conditions.

4. 4.) Gloved Touch

            The improved algorithm on PCAP touch controller firmware enables the touchscreen manufacturer to              be able to tune the projection field for different applications, thus enabling workers to keep their                      thick working or safety gloves on while operating on their HMI equipment.

5. 5.) Thick Cover Lens

            To improve precision, certain PCAP touch screens now include a thicker glass which will detect fewer              signals while increasing the signal strength and maintain an optimal noise ratio.

Where would a Resistive Touch Screen still be used?

When it comes to a resistive touch screen, you need to push a little harder for your touch to get detected and they cannot recognize  multiple touches at the same time. Nevertheless, these applications still find a lot of value and are widely used in many markets.

These touch screens are durable and affordable, so they are widely used in credit card readers, many defense applications, points of sale, medical equipment, and consumer markets. In these instances, the resistive touch screens deliver the exact features needed for the display. Here is a list of advantages that still make resistive touch screens a great solution for these categories and more. 

Advantages of Resistive Touch Screens:

          1.) Less complex to make which results in a lower product cost

          2.) Can be used with bare finger, gloved finger, stylus, etc

          3.) Does not respond to contact from outside stimuli (ex: dust and water splashes

Conclusion:

Both capacitive and resistive touch screens can offer a durable, high-quality, crystal-clear image solution. However, there are a few key advantages of choosing a capacitive touchscreen over a resistive touchscreen for industrial applications. 

The recent improvements of PCAP touchscreen technology have increased performance with breakthroughs in IC controllers, driver and firmware, which increase precision, and reduce EMI noise. As a result, you can leverage PCAP touch technology for better durability, improved scratch resistance, and greater touch precision for your industrial applications. 

About E3 Displays:

High performance and dependability is needed from industrial displays. E3 provides solutions that give you peace of mind during the busiest work environments. With over 20 years of combined experience in display technology, E3 Displays has everything you need to develop and manufacture your custom touch display all in one place. With customer-centric solutions featuring strategic planning, competitive pricing, longevity and support, we ensure the best products on the market to help you scale.

Both capacitive and resistive touch screens can offer a high-quality, crystal-clear image. However, there are a few key advantages of choosing a capacitive touchscreen over a resistive touchscreen. As explained here, advancements in PCAP Technology are replacing Resistive as the go-to for Industrial Applications.