There are many methods to improve the measurement accuracy of split ultrasonic level gauges, and the following are some of the main methods:

1. Optimize installation method

Ensure vertical installation: The direction of the ultrasonic transducer should be kept perpendicular to the liquid surface, so that sound waves can be emitted and received vertically, reducing measurement errors caused by inclined installation. If the installation is not vertical, the incident angle and reflection angle of the sound wave on the liquid surface will change, affecting the accuracy of the measurement.

Choose a suitable installation location: It should be installed in a calm and unobstructed area, avoiding installation near the liquid inlet, outlet, mixer or other places that are prone to interference. For example, in containers with agitators, they should be installed as far away from the agitator as possible to avoid bubbles and liquid level fluctuations caused by agitation affecting the measurement.

2. Perform temperature compensation

Understanding the effect of temperature on sound velocity: The propagation speed of sound waves in air varies with temperature, with a change of approximately 0.18% in sound velocity for every 1 ℃ increase or decrease in temperature. Therefore, temperature monitoring and compensation are needed to improve measurement accuracy.

Adopting built-in temperature sensor: Some split ultrasonic level gauges are equipped with built-in temperature sensors, which can monitor the ambient temperature in real time and compensate for the speed of ultrasonic waves in the algorithm.

3. Overcome false echoes

Identify the source of false echoes: false echoes may come from foam, suspended objects, obstacles, etc. on the liquid surface. These false echoes can be mistaken for echoes from the real liquid surface, resulting in inaccurate measurement results.

Adjusting sensitivity and damping time: By adjusting the sensitivity and damping time of the ultrasonic level gauge, some false echoes can be filtered out. Properly reducing sensitivity can reduce the detection of false echoes, and increasing damping time can make the measurement signal more stable.

4. Reduce transit time error

Add Time Control Circuit (TGC): The TGC circuit can automatically adjust the gain of the received signal based on the attenuation of sound waves, so that the amplitude of the signal reflected back from different heights of the liquid surface is basically the same, thereby reducing timing errors caused by differences in signal amplitude.

Using a zero crossing detection circuit: By differentiating the received signal, a stop timing signal is generated using the zero crossing detection circuit. This signal is located at the time center of the echo signal and is not affected by the signal amplitude, effectively eliminating transit time errors.

5. Consider system errors and make corrections

Calibration system latency: System errors are mainly caused by system latency, including hardware circuit latency, interrupt response latency of microcontrollers, probe response latency, etc. The system delay can be calibrated and corrected by testing a fixed distance.

Correction of acoustic center point distance: When measuring liquid level with ultrasound, the liquid level distance is from the front surface of the probe to the liquid level, but the piezoelectric ceramic acoustic center is not on its surface, which can cause system errors. It is necessary to classify the error caused by this distance and the time delay difference into one category and make corrections.

6. The split ultrasonic level gauge adopts real-time sound speed compensation

Installation of sound path bracket: Install a baffle at the front end of the transmitting probe to form a fixed distance sound path interval. When the probe emits sound waves, the baffle reflects a portion of the sound waves back to the probe. By calculating the time from emission to reception, the speed of sound is determined.

Selecting suitable materials: The sound path frame should be made of materials with low temperature expansion coefficient to avoid changes in the distance of the sound path caused by environmental temperature changes, which may affect the accuracy of the measured sound speed.