A method of the untouched ultrasonic liquid level measurement with high precision

In order to improve the precision of the ultrasonic liquid level measurement in the airtight container,the principle of ultrasonic distance measurement is described and the main error sources are analyzed. In views of the error sources, the ultrasonic emission circuit which is propitious to reduce the blind distance, the temperature measured circuit which amends the ultrasonic velocity, the automatic gain regulated circuit which compensates the ultrasonic attenuation are designed and the method which checks up the preceding edge of echo by setting up the double compared values was used in the software, which contribute to enhance the measurement precision. Experiment shows that the ultrasonic liquid level apparatuses which adopt these methods have the higher precision, its circuits is simpler,easier implement than the others.