Further study on linearization of echo intensity sensing type ultrasonic liquid level transducer

The echo intensity sensing type ultrasonic liquid level transducer has the advantage of a simpler design compared to that of the conventional time of flight (TOF) type linear transducer, but it has a non-linear characteristic. A further study on a simple linearization technique of this non-linear transducer is described in the present paper. The proposed linearized system consists of an additional reference cylinder partially filled with liquid up to the reference zero level. The cover plate of each cylinder carries an identical set of ultrasonic transmitting and receiving probes. For the transmitting probes supplied from the same excitation source at 40 kHz, the echo intensities of the waves in the two cylinders are measured by two receiving probes and two identical signal conditioner circuits, which give the output DC voltage signals In constantly varying with the variation fluid depth. The proposed linearization circuit utilizes these two signals to give a final DC output signal varies in a linear fashion with changes in liquid level. The characteristic equations of a prototype model of the transducer unit outlined in the paper are found to be supported by the results of the repeated experiments.