The fluid-level sensor has an acoustic waveguide comprising a flexible metal rod, an electroacoustic transducer coupled to one end of the acoustic waveguide and an acoustic resonator coupled to the other end of the acoustic waveguide. The flexible metal rod has two ends, one cylindrical waveguide coupled via a conical acoustic concentrator to one end of the flexible metal rod, the other cylindrical waveguide coupled via a conical concentrator to the other end of the flexible metal rod. One cylindrical waveguide is coupled to the electroacoustic transducer and the other cylindrical waveguide is coupled to the acoustic resonator. The structure provides for the enhanced functional capabilities of the sensor by using it under the conditions of high temperature, radiation, strong electromagnetic interference, intense vibrations, impacts, and other negative factors. The sensor can be installed, maintained, and repaired without hazard to servicing personnel.

A method (100) for estimating a volume of fuel available in a fuel tank (6) of a transport vehicle (1), the tank (6) comprising a tank wall inside which a space is defined for containing fuel, the method (100) comprising, in sequence, the steps of: a) exciting (101) a vibration of the tank (6); b) acquiring (102) a response signal correlated to a frequency response produced by the tank (6) due the excited vibration; c) processing (103) the acquired response signal to obtain an estimate of the initial volume of fuel available in the tank (6); d) gradually taking (104) fuel from the tank (6) with the transport vehicle (1) in use; e) estimating (105) a quantity of fuel taken gradually from the tank (6); f) estimating (106) the volume of fuel available in the tank (6) based on the initial volume and quantity estimate of fuel taken gradually.

A method and apparatus to measure the fluid depth in a well or borehole is described. The approach reduces the effects of acoustic noise occurring near the top of the well or borehole that can interfere with the fluid depth measurement. A resonant acoustic structure between an acoustic transducer and the well or borehole provides efficient coupling of spectrally narrow acoustic signals into the well or borehole, as well as providing a bandpass acoustic filter on the returning signal, to improve the signal to noise ratio of the desired acoustic reflection.

A tank-in-tank fill level indicator, making use of noninvasive tank-in-tank measuring techniques. A vibration device, such as an exciter or resonator, vibrates the outer tank at its natural frequency of vibration, thereby inducing the vibration of the inner tank and a beating effect as a result of the interaction of the vibrations of the two tanks. A vibration detection device, such as an accelerometer, detects the resultant beating effect of the two tanks' induced vibrations. A data processing device, such as a microcontroller, processes the detection data to obtain the liquid volume. A display, wired or wireless data transmission device, or combination thereof, is then used to provide tank or container fill-level information.

A liquid container refill management system including a machine learning algorithm and method of training the same, the system and method making use of noninvasive tank-in-tank measuring techniques. The system can comprise of a container fill level indicator. The container fill level indicator can be capable of detecting a vibration response signal on the outer surface of a container, wherein the system is capable of transmitting the response signal to a remote data processor for processing using a trained machine learning algorithm. The trained machine learning algorithm can be trained by the process of selecting model inputs and outputs to define an internal structure of the machine learning algorithm, applying a collection of input and output data samples to train the machine learning algorithm, and verifying the accuracy of the machine learning algorithm by applying input data samples and comparing received output values with expected output values.

In an example, a method comprises fabricating a first validation device for association with a first replaceable print apparatus component. The device may be to form part of circuitry arranged on the first replaceable print apparatus component, and may provide an associated electrically detectable characteristic which varies with the position of at least part of the first validation device. The electrically detectable characteristic may be measured and data indicative of the characteristic may be stored in a first memory. The first replaceable print apparatus component comprising the first device and the first memory may be assembled.

A resonance circuit (2) includes a capacitor (C1) and an inductor (L1, L2) of which an inductance is changed depending on developer including toner, and generates an output voltage corresponding to the inductance. A detecting circuit (3) detects the toner on the basis of the output voltage. An adjustment-purpose closed circuit (4) includes a semi-fixed resistor (VR1) and an adjustment inductor (L3) that forms magnetic coupling with the inductor (L1, L2), and causes an inductance of the inductor (L1, L2), a resonance frequency of the resonance circuit (2), an amplitude of the output voltage and a detected toner amount to be adjustable with a variable resistance value of the semi-fixed resistor (VR1).

An exemplary liquid tank level measurement system includes a tank having a wall, an accelerometer attached to the wall and configured to measure a vibration in the wall, and an instrument electronically connected to the accelerometer, the instrument configured to communicate a liquid level condition responsive to a vibration measurement received from the accelerometer.

A liquid surface sensor includes a hollow member having a first opening end and a second opening end, and a sensor unit provided so as to close the first opening end of the hollow member. The sensor unit includes a vibration plate, and a piezoelectric element which is provided on the vibration plate and is formed by laminating a first electrode film, a piezoelectric film, and a second electrode film in a thickness direction of the vibration plate.

A device for providing a gas and temperature compensated acoustic measurement of the level of a liquid surface, including a transmitter, a receiver, and a waveguide for guiding acoustic signals. The waveguide includes a reference portion extending from a first end to a reference element, and a measurement portion extending from the reference element towards the end. The device further includes a channel extending from at least one inlet in said reference portion to at least one outlet in said measurement portion, the channel being separated from the waveguide so as to provide a fluid flow independent of the waveguide, and a gas-pump arranged to create a gas flow in said channel from said at least one inlet to said at least one outlet.