Dayu Guide: How to Handle Mismatch Between Ultrasonic Level Meter mA Value and PLC

　　At a customer site in Shanxi, the mA value of an integrated ultrasonic level meter did not match the PLC. The customer contacted Dayu's technical staff. Under their guidance, they tested the mA with a multimeter and found a deviation. After adjusting the calibration values for 4mA and 20mA, the meter worked normally.

　　Another customer from Zhejiang sent Dayu's after-sales team an echo profile of their ultrasonic level meter to check if the readings were correct. From the echo profile, two peaks can be seen—meaning the ultrasonic signal reached two planar surfaces and reflected back—indicating that the riverbed underneath is uneven. Looking at the two rows of numbers, the lower right shows 0.039 meters, which represents the liquid level value. This value is incorrect; the display will only show correctly when there is water present.

　　Speaking of echo profiles, it is worth explaining the working principle of the ultrasonic level meter. The principle is that the ultrasonic transducer (probe) emits high-frequency pulse sound waves that reflect off the surface of the measured material; the reflected echo is received by the transducer and converted into an electrical signal. Therefore, the measured surface must be smooth. If the surface is uneven, signal interference can occur, causing inaccurate measurement data.

　　Because the ultrasonic level meter uses non-contact measurement, the measured medium is almost unrestricted, which has led to its widespread use in recent years for measuring the height of various liquids and solid materials.