Ultrasonic level gauges, as non-contact level measurement instruments, are known for their high measurement accuracy, simple installation, and minimal maintenance requirements. They are commonly used to measure the liquid level in various types of containers.
Under normal temperature and pressure conditions, ultrasonic level gauges are an optimal choice for level measurement, offering reliable operation, easy installation, and minimal maintenance. They are particularly effective for measuring the level of viscous, corrosive, turbid, and other challenging liquids. Correct positioning and proper installation are crucial prerequisites and key factors for the reliable operation of an ultrasonic level gauge. They are generally not suitable for use in vacuum or negative pressure environments, as the rarefied air alters the speed of sound, leading to measurement errors. Additionally, increased sound wave attenuation in such conditions can reduce the effective measuring range or even prevent measurement entirely.
Analysis of Common Issues with Ultrasonic Level Gauges
Measurement Inaccuracy Due to Power Supply Voltage Fluctuation
In single-probe measurement systems, where the same probe acts as both transmitter and receiver, applying an excessively high excitation voltage during ultrasound transmission can increase the blind zone distance, potentially shifting the measurement range beyond its intended limits. Conversely, if the probe voltage is too low, the returning echo signal from distant measurements might be too weak to detect. This can cause a previously functional system to malfunction or produce measurement errors. The solution is to adjust the power supply voltage to the rated value to ensure normal probe operation.
Inappropriate Measuring Range Selection
Due to the inherent existence of a blind zone and the attenuation of ultrasonic waves during propagation, ultrasonic level measurement has a finite range; it is not unlimited. Therefore, it is essential to select a probe and operating mode with a suitable range for the specific application.
Probe Entering the Blind Zone
Every ultrasonic level gauge has a specific blind zone. When the probe enters this blind zone, ultrasound cannot measure accurately, often resulting in a full-scale reading or erratic data. For example, for gauges with a range up to 5 meters, the blind zone is typically 0.3-0.4 meters; for ranges up to 10 meters, the blind zone is usually 0.4-0.5 meters.
Faults Caused by the Measured Liquid Surface Condition
If the measured liquid surface is covered with debris or is highly uneven, the ultrasonic waves may experience diffuse reflection, or the beam may be reflected away from the probe. If the amount of ultrasound returning to the probe is insufficient and falls below its sensitivity threshold, the probe will fail to detect the echo and will not function correctly. In such cases, installing a protective stilling well (e.g., a wire mesh enclosure) below the measurement probe can help.
Impact of Installation Method
Improper installation can lead to operational issues. Ultrasonic level gauges have a blind spot, analogous to the blind spot in human vision. The size of this blind zone depends on the gauge’s range: a smaller range corresponds to a smaller blind zone, and a larger range corresponds to a larger one, though it is typically controlled within a range of 30 cm to 50 cm. Consequently, this characteristic must be fully considered during installation. The measurement probe (sensor) must be installed vertically. If installed at a tilt, the ultrasonic beam will deviate from its intended path, preventing the probe from receiving the necessary echo signal. Furthermore, the distance between the probe and the liquid level is critical; the probe must be positioned appropriately.
Maintenance of Ultrasonic Level Gauges
Regular Cleaning
Ultrasonic level gauges should be cleaned regularly to prevent the sensor from being covered by dirt or debris, which could cause the device to malfunction. Use pure water or a mild cleaning agent for cleaning, and avoid harsh chemicals.
Routine Care
Ultrasonic level gauges should be inspected periodically to ensure normal operation. During use, keep the device dry and clean, and protect it from moisture and water exposure. Also, ensure all connections are correct and secure to prevent loosening.
Timely Replacement of Parts
If the ultrasonic level gauge sensor or other components develop faults, they should be replaced promptly. Before replacement, disconnect the device’s power supply and dismantle it as needed. After replacement, conduct thorough testing to verify the device operates normally.