Description of gas characteristics, echo filter and sensor calibration

Depending on the measurement method chosen, fluid characteristics and environmental characteristics must be known.

Gas characteristics
Gas characteristics can affect the measurement results of ultrasonic sensors. The propagation speed of ultrasonic waves is related to temperature and gas (see the table in 5.4.2). There may be multiple gas mixtures between the liquid and the sensor, and we must determine the characteristics of these gas mixtures by two-point calibration. The temperature sensor on the ultrasonic level transmitter measures the temperature of the storage and irrigation, so that the liquid level measurement can be automatically compensated.

Echo filter
Any object that is exposed to ultrasonic waves (eg, agitators, inlet tubes, mountings, etc. in the tank) will reflect, so measurements may be affected or incorrect measurement signals may be generated. The level transmitter detects and eliminates these interference echoes by performing echo filtering.
Sensor calibration
Ultrasonic level measurement is the distance between the sensor and the liquid level. If the distance from the sensor to the bottom of the tank is known, then the tank level can be calculated and displayed. Also as the geometry of the tank is known, the filling volume can also be calculated and displayed. For tanks with complex geometries, we can also determine the relationship between distance and volume by online calibration (for example: step by step from point 1 to point 5, see figure below).
When measuring static pressure, the density of the liquid must be known to convert the pressure measurement to a liquid level. If the geometry of the tank is known, then by step-by-step measurement we can also determine the volume. Depending on the characteristics of the pressure transmitter, the volume value can be displayed or calculated by the PLC.