SAW Touchscreens: What Are Transducers and How Do They Work

When researching the parts of a typical surface acoustic wave (SAW) touchscreen, you may come across the transducers. SAW touchscreens still have an integrated display, such as a liquid-crystal display (LCD). And the integrated display typically features its own backlighting, such as light-emitting diodes (LEDs). But SAW touchscreens use a different design than that of other touchscreens.

SAW touchscreens use ultrasonic waves to detect touch commands. SAW is the only touchscreen technology, in fact, that uses ultrasonic waves. Resistive touchscreens use pressure, whereas capacitive touchscreens use capacitance. SAW touchscreens are distinguished from their capacitive and resistive counterparts by their use of ultrasonic waves. All SAW touchscreens need transducers to detect touch commands via ultrasonic waves.

Transmitting Transducers

There are two types of transducers used on SAW touchscreens: transmitting and receiving. Transmitting transducers are designed to send and transmit ultrasonic waves.

Upon powering up a SAW touchscreen, the transmitting transducers will immediately project ultrasonic waves across the display interface. You won’t be able to see, feel or hear these ultrasonic waves. Nonetheless, the SAW touchscreen will use them to detect touch commands. Transmitting transducers are small devices — typically found on the corners of edges of a SAW touchscreen — that project ultrasonic waves across the display interfaces.

Receiving Transducers

Receiving transducers, on the other hand, are designed to sense and receive ultrasonic waves. Transmitting transducers alone won’t allow SAW touchscreens to detect touch commands. The transmitting transducers will project ultrasonic waves across the display interface, but SAW touchscreens still need some way to sense and receive those ultrasonic waves. Receiving transducers are used for this purpose.

Transmitting transducers work in conjunction with receiving transducers. The transmitting transducers will project ultrasonic waves. As these ultrasonic waves are released, they will travel across the display interface before being “picked up” by the receiving transducers on the opposite side.

If you perform a touch command on the display interface, you’ll disrupt the ultrasonic waves. The SAW touchscreen will register this disruption as a touch command. Whether you use a finger, stylus or any other object, you’ll block the ultrasonic waves. The receiving transducers will detect this disruption, and the SAW touchscreen will respond with the appropriate action.

In Conclusion

SAW touchscreens use transducers to detect touch commands. They use transmitting transducers to project ultrasonic waves across the display interface, and they use receiving transducers to sense and receive these ultrasonic waves.