To measure our ultrasonic transducers, we use a proven test circuit internally at SECO. This forms the basis for the technical data in our product data sheets. This circuit can be reproduced for the initial installation of our products. Of course, our ultrasonic transducers can also be operated with a wide variety of customer-specific test circuits. For tips and tricks, please contact our ultrasonic experts! We look forward to hearing from you.

Measurement setup & test circuit

Pulse-echo mode

Transmitter-receiver mode

Electronic accessories

Driving electronics / DAC:

• Excitation of the ultrasonic transducer
• Generation of pulse or sinus burst signal and frequency control

Antiparallel diodes z.B. BAV20:

• Smoothing of the signal, protection of sensitive electronic components from voltage peaks

Reflector at defined distance:

• only in pulse-echo mode
• at least 100 x 100 mm, flat surface
• longitudinal axis vertical to the transducer

amplifier:

• if oscilloscope / ADC has no integrated amplification unit
• especially for high-frequency transducers with low echo voltages
• Increased signal-to-noise ratio, bandpass to suppress interfering frequencies

Oszilloscope /ADC:

• Digitization and evaluation of the received signal
• Signal visualization with regard to signal shape
• Amplitude and frequency in real time, frequency analysis

BNC connection cable (recommended):

• Better signal quality, minimized signal distortion, especially at high frequencies
• Maximum freedom from interference, connection stability

Transducer-specific settings of the test circuit

We basically distinguish between three types of transducer, which we have optimized for their different strengths in terms of their electro-acoustic functionality and design.

Electroacoustic parameters

Measured with our SECO-specific test circuit, the following electro-acoustic parameters result for our product groups:

General conditions for measuring the electroacoustic parameters:

• Excitation type, burst cycles and distance between transducer and reflector see “Transducer-specific settings of the test circuit”
• Size of the reflector at least 100 x 100 mm, longitudinal axis of the transducer vertical to the reflector
• Medium air at room temperature and a relative humidity < 25 %

Signal diagram

Typical echo signal of an ultrasonic transducer after Sinus excitation:

Details of the signal curve:

• UA = ringdown voltage
• UE = echo voltage
• bc = number of burst cycles
• rc = number of echo-ringdown cycles (UE to 1/2 UE)

Typical directivity plot

Directional characteristic and opening angle of focused and multi-use transducers

Typical directivity plot multi-use transducer (transmitter)

Focused transducers are characterized (according to their name) by a very small beam width and a small opening angle. Typical values here are approx. 7…11° (@ -3dB sound pressure). Comparatively long ranges are possible with them, which is why they are often used for distance measurement, level measurement, presence detection, etc. In contrast, our multi-use transducers have a particularly wide sound beam and large opening angles of typically approx. 12…20° (@ -3dB sound pressure). These transducers are primarily used in areas where the sound beam is dispersed (wind measurement in an anemometer, flow measurement). A wide sound beam enables precise measurements even at very high flow velocities.

Background information on the test circuit

Ultrasonic transducers generate and receive sound waves in the ultrasonic range. Their functionality and performance are tested using a test circuit. This comprises several key components. First, a function generator or high-voltage generator is used to generate an electrical signal that drives the ultrasonic transducer. This signal is then passed through a power amplifier to ensure it is strong enough to activate the transducer.

The transducer itself converts the electrical signal into mechanical vibrations that are emitted as ultrasonic waves. These waves can then be detected by a receiver, often a second transducer. The receiver transducers the ultrasonic waves back into an electrical signal.

This signal is then amplified by a preamplifier and sent to an oscilloscope or spectrum analyzer. With these instruments, the user can analyze the frequency, amplitude and shape of the received signal. By comparing the output and input signals, the performance and accuracy of the ultrasonic transducer can be evaluated. These test circuits are essential to ensure that ultrasonic transducers perform accurately and reliably in medical, industrial and scientific applications