Accurate liquid level detection using ultrasonic sensors

In laboratory automation , a large number of microbial culture well plates and test tubes are used to analyze liquids. The new ultrasonic sensor can quickly detect the liquid level with an accuracy of 0.1mm. Laboratories are also beginning to use more and more automated equipment to complete test and inspection tasks, such as testing and analyzing reagents, sample pipetting, etc. The sensors used in these tasks should be able to work accurately and provide traceable results, and must also have a high detection speed. For example, at a liquid medium inspection station, an important step is to fill a small glass test tube with a liquid medium for inspection and analysis, such as blood to be analyzed. After a small amount of test sample is poured into the tiny test tube, the liquid level of the liquid medium in the tiny test tube needs to be detected before the inspection and analysis begins. The openings of these tiny microbial culture vessels are very small, and some microbial culture bottles have a diameter of only 3mm, but the sensor is still required to accurately detect the capacity of the liquid medium in the bottle in the shortest time. The capacitive detection technology currently used does not achieve the ideal detection accuracy. Although independently set photoelectric sensors meet the requirements of detection accuracy, they are expensive.

Ultrasonic sensors detect each culture bottle in the culture bottle tray

Ultrasonic sensors are detection sensors that do not come into contact with the medium they are in contact with. This feature is very meaningful in laboratory applications: it ensures that the sensor is not corroded and that the measured medium does not cross-contaminate. In addition, ultrasonic sensors are very insensitive to humidity and dust in the surrounding environment, which ensures that they can work accurately and stably for a long time.

Compared with photoelectric sensors, ultrasonic sensors do not generate light, but use sound waves for detection. Therefore, they can reliably detect media of different properties and are independent of the transparency and color of the measured medium. Regardless of the viscosity of the measured medium, it will not affect the test results.

The continuously working ultrasonic sensor emits a cone-shaped sound wave to the measured object. This cone-shaped sound wave can just enter the bottle mouth with a diameter of less than 10mm to detect the liquid level in the bottle. In order to avoid being restricted by other factors during use, the manufacturer worked closely with the user to develop a new 09 series ultrasonic sensor. This new ultrasonic sensor is equipped with a specially designed ultrasonic emission nozzle, which makes the emitted ultrasonic beam smaller in diameter and can enter the culture bottle with a diameter of 3mm. Depending on the structure, this ultrasonic sensor can be configured as a vertical or horizontal sensor. The ultrasonic emission nozzle can also be easily removed and replaced, which greatly facilitates the cleaning operation of the sensor.

The accuracy and repeatability of this sensor are very high, up to 0.1mm; its shortest detection time is only 7μs. Since the diameter of the sensor housing is only 9mm, it can be well arranged on the entire culture bottle tray. In this way, the same number of ultrasonic sensors can be set according to the number of culture bottles in a row in the tray, and one row of culture bottles can be detected at a time, which further improves the detection speed and shortens the detection time.

The same ultrasonic sensor can also be used to check the size of the free space above the culture bottle. In this way, one type of sensor can be used to complete the two tasks of liquid level inspection and review.

Even in the production process outside the laboratory, this ultrasonic sensor has a wide range of uses. For example, it can detect whether the tablets are in place or whether the medicine is put into the blow-molded package.