Precautions for Using Ultrasonic Level Meters
Summary: Ultrasonic level meters are widely used in various environments such as water, acids and alkalis, slurry, and food.
An ultrasonic level meter is a digital level instrument controlled by a microprocessor. During measurement, pulsed ultrasonic waves are emitted by the sensor; the sound waves are reflected off the liquid surface and then received by the same sensor and converted into an electrical signal. Ultrasonic level meters feature automatic power adjustment, temperature compensation, and anti-interference capabilities. Because they use non-contact measurement, the measured medium is virtually unrestricted. Ultrasonic level meters are widely used in various environments such as water, acids and alkalis, slurry, and food.
Precautions for Using Ultrasonic Level Meters
1. Range and Target Size
The size of the object to be detected by an ultrasonic level meter directly affects the maximum range of the ultrasonic sensor. The sensor must detect sound at a certain sound level before it can produce an output. Large objects reflect most of the sound back to the ultrasonic sensor, allowing the sensor to detect them at its maximum sensing distance. Small objects reflect only a small portion of the sound, which greatly reduces the sensing range.
2. Objects to Be Detected
The ideal target for ultrasonic detection by an ultrasonic level meter should be large, flat, and dense, and perpendicular to the front face of the transducer. The most difficult objects to detect are small objects made of sound-absorbing materials (such as foam rubber), or objects positioned at an angle to the transducer. Certain hard-to-detect objects can be detected by having the sensor detect a background surface and then respond to the target object between the sensor and the background.
If the liquid surface is still and perpendicular to the sensor face, detecting the liquid is easy. If the liquid surface fluctuates significantly, the sensor's response time can be extended to average out the fluctuations and obtain more consistent readings. However, ultrasonic level meters cannot accurately detect liquids with a foamy surface, because foam deflects the direction of sound propagation.
3. Vibration
Vibration—whether from the sensor itself or from nearby machinery—can affect the accuracy of distance measurement by an ultrasonic level meter. Rubber anti-vibration mounts can be used when installing the ultrasonic level meter to reduce such problems. Guide rails can also sometimes be used to eliminate or greatly reduce component vibration.
4. Attenuation
The sensor is also designed with a temperature compensation function to adjust for slow changes in ambient temperature. However, it cannot compensate for temperature gradients or rapid changes in ambient temperature.
5. False Measurement Results
Objects near the ultrasonic level meter (such as guide rails or mounting rods) may reflect sound waves. To accurately detect the target object, the influence of nearby sound-reflecting surfaces must be reduced or eliminated. To avoid false detection of nearby objects, ultrasonic level meters are equipped with an LED display to guide operators during installation, ensuring correct sensor installation and reducing the risk of false measurements.