TDK Announces Series of New Ultrasonic Sensor Disks

TDK’s EPCOS division unveiled a new series of ceramic-based EPCOS ultrasonic sensor disks.

The series is comprised of two standard types: the B59050Z0206A030 and the B59070Z0285D120/1 sensor disks.

The B59050Z0206A030 sensor disk has a diameter of 5.0 mm and a thickness of 1.02 mm and is suitable for use in liquid media. The B59070Z0285D120/1 has a diameter of 7.0 mm and a thickness of 0.195 mm and is suitable for operation exposed to air.

 

The B59050Z0206A030 (left) and the B59070Z0285D120/1 (right). Image from TDK

What Are Ultrasonic Sensor Disks?

As described in a TDK application note, ultrasonic sensor disks work in a manner analogous to radar. The difference is that instead of radio waves, the disks make use of sound waves at frequencies well above the range of human hearing. 

The disk emits a sound packet. If it hits a target, it bounced back and the disk detects it. The time of the round trip is divided in half to represent the distance between the disk and the target. Since the velocity of sound in air is known, the distance (D = Velocity x Time) is readily obtained.

How Do Ultrasonic Sensor Disks Work

Ultrasonic sensor disks are based on the piezoelectric effect. 

To generate the sound packet, an electric field is applied, and it will respond with expansion or contraction in synch with the changing field. Conversely, if the sound wave is reflected back by a target, it will apply pressure to a piezoelectric material leads to the generation of a voltage across the electrode surfaces.

Because of this duality, a single ultrasonic sensor disk suffices for both emission and detection of sound waves.

Resonance Modes

TDK’s ultrasonic sensor disks are designed for either radial oscillation or thickness oscillation. The radial mode corresponds to a periodic oscillation of the radial dimension of the disk, while the thickness mode corresponds to a periodic oscillation of the disk’s thickness.

 

Radial mode oscillation and thickness mode oscillation. Image modified from TDK

 

The B59050Z0206A030 has a serial resonance frequency of 2000 kHz, it features thickness oscillation mode (axial), making it suitable for use in liquid media.

The B59070Z0285D120/1 has a radial mode of oscillation at 285 kHz, and is suitable for operation exposed to air.

Main Applications

Automotive

• Park assist and blind-spot monitoring systems
• Level measurement for fuel or SCR (Selectiver catalytic reduction) tanks
• Interior monitoring for anti-theft systems

 

Industrial

• Flow metering of fuels or gases
• Level sensing of fluids or bulk materials
• Collision avoidance systems in automated vehicles

Packaging

The packaging differs between the three devices, though 

• B59070Z0285D121 is packaged 50 devices per tube
• B59070Z0285D120 is packaged 245 devices per tube
• B59050Z0206A030 is packaged 1000 devices per tray 

All devices are RoHS-compatible and have a temperature range from -40 °C up to 160 °C.

Around the Industry

Ultrasonic sensors come in all sizes, shapes and serve a variety of purposes. Many manufacturers offer a very wide range of products. Piezodata, for example, offers a range of sensors optimized for the industrial environment. The range over which they can detect objects or detect fluid levels ranges from 40 mm to 3 meters. They operate at frequencies ranging from 75Khz ~ 400Khz.