Novel dual-frequency non-contact ultrasonic level transducer
Nowadays, non-contact ultrasonic level transducers have been widely used for short-distance object detection, in particular, for liquid, solid and powder level detection. Their wide applications are not limited by the type of object detected, regardless of colors, transparency, hardness, etc. However, the general non-contact ultrasonic level transducers currently available on the market are just with single operating frequency, facing the dilemma of detection distance and the blind zone. Generally speaking, the ultrasonic transducer with lower operating frequency has longer detection distance along with a longer blind zone and poorer resolution; on the contrary, the ultrasonic transducer with higher operating frequency has shorter detection distance along with a shorter blind zone, and better resolution. The blind zone means the minimum detection distance from the surface of the ultrasonic transducer. The main factor affecting the blind zone is ringing. When the ultrasonic transducer is driven by specific frequency of electronic driving power, the piezoelectric ceramic correspondingly generates vibration and emits ultrasonic waves simultaneously, but this vibration does not stop immediately when the driving power is cut off. It fades away gradually to a static state after the remaining vibration is absorbed completely by the back damping layer of the transducer. The duration between the end of vibration and the static state is called ringing. The longer ringing, the longer the blind zone. If the blind zone overlaps with the echo signals, the actual time of flight (ToF) cannot be calculated and therefore cannot detect the real distance, as shown in figure 1.
Unictron has successfully developed a novel type of dual-frequency ultrasonic air transducer with innovative technologies, which can operate at both lower operating frequency and higher operating frequency “50/200 kHz dual-frequency non-contact ultrasonic level transducer.” This provides the advantage of maximizing detection distance and minimizing the blind zone in one transducer, making the application of the transducer more flexible, and its sensing range can cover most of non-contact ultrasonic level transducers on the market, as shown in figure 2.
In comparison with the general 50 kHz non-contact ultrasonic level transducers, Unictron’s 50/200 kHz dual-frequency non-contact ultrasonic level transducer has significantly higher sensitivity and much better reliability. The traditional 50 kHz air transducer on market has a maximum sensing range of less than 10 meters along with poor thermal cycle reliability, less than 5 thermal cycles. Unictron’s dual-frequency air transducer reaches a maximum sensing range up to 12 meters at 50 kHz operating frequency with thermal cycle reliability of more than 10 cycles. Furthermore, the blind zone of the general single-frequency 50 kHz air transducer is around 30 cm, in other words, within 30 cm, the single-frequency 50 kHz air transducer cannot detect any objects. The blind zone of the dual-frequency 50/200 kHz air transducer can be less than 10 cm, which greatly improves the blind zone of the single-frequency 50 kHz air transducer. A comparison between dual-frequency and single-frequency air transducers is listed in table 1.
|Items||Dual-frequency air transducer||Single frequency air transducer|
|Operating Frequency (kHz)||50/200||50|
|50/200 kHz dual-frequency||Single-frequency|
|Dimension-OD (bottom face) (mm)||56||56|
|Max. Sensing Range (meter)||12||10|
|Blind Zone (cm)||10||30|
|Directivity (Full Angle @-3 dB)||
10 degree (@50 kHz)
6 degree (@200 kHz)
|thermal cycle||> 10 cycle||< 5 cycle|
Table 1: Dimensions and characteristics comparison table
Ultrasonic Level Transducer you need!
The global demand for ultrasonic transducers for level measurement continues growing, but all non-contact ultrasonic level transducers currently on the market operate at single operating frequency, therefore an inevitable compromise between the maximum detection distance and the blind zone. The standard 50 kHz non-contact ultrasonic level transducer can only be used for level detection in the range of 0.3 ~ 10 meters, where the blind zone is too long to meet the requirement of users. Unictron has developed the unprecedented dual-frequency 50/200 kHz non-contact ultrasonic level transducer that surpasses the existing 50 kHz transducers on the market, combining a longer sensing range and minimizing the blind zone in one transducer, which can cover most non-contact level transducers on the market to meet customer needs with high performance and high quality. The advantages of dual-frequency solution predestine its usage to prevail over single frequency transducers.