A method and device for measuring the fluid level in a container. A column f fluid within the container is momentarily subjected to pressure, which causes the column of fluid to vibrate. The oscillation frequency is then measured. Since the frequency depends on the fluid level, the fluid level may be determined from the frequency of oscillation.

A vibrating cylinder pressure transducer system with an incorporated error correction circuitry is disclosed. The compensation circuitry includes a microcomputer, a frequency counting circuit and a arithmetic processor. The system further provides for digital temperature measurement and compensation. The characterizing equation of the vibrating transducer is solved by the microcomputer and the arithmetic processor in order to provide a thermal compensated, highly accurate digital output indication of the measurement of pressure in a single self-contained unit which is small in size and which provides a direct engineering unit output thereby eliminating the need for a further and separate dedicated computer in order to obtain pressure measurements.

An article inspection apparatus is capable of inspecting an article which cannot be sorted out by image processing or a diagnostic process that employs energy to be transmitted through the article. A hitting sound is generated by a hitting sound generating device when an article is hit, and is detected by a sound detecting device and analyzed by a detected-sound analyzer. The analyzed result is converted into a pattern by a detected-sound pattern generator, and the pattern is matched with registered reference patterns from a reference pattern registering device by a pattern matching device. Based on the result of matching, the article is sorted out by an article sorting device. It is possible to detect the material of a container, such as cans of aluminum and iron which are identical in shape and size to each other. It is also possible to check the amount of a substance in a container that cannot directly be seen, or inspect baked articles for pores contained therein.

A method and an apparatus are provided for measuring the pressure of a gas within a sealed vessel. A sonic transducer is used to apply an oscillating force to the surface of the vessel. The frequency of the ultrasonic wave is swept through a range which causes resonant vibration of the gas in the vessel. A receiving transducer measures the amplitude of the resultant vibration at the vessel surface and reveals the resonant frequency of the gas as peaks in the amplitude of the sweep. The resonant frequency obtained depends upon the composition of the gas, its pressure and temperature, and the shape of the confining vessel. These relationships can be predetermined empirically so that the pressure inside the vessel can be calculated when the composition of the gas, its temperature, and shape of the confining vessel are known. The output of the receiver is fed into a computer which is programmed to calculate the pressure based upon these predetermined relationships which are stored in the computer.

A system for analyzing the fill characteristics of a container. A container having a filling material therein is positioned adjacent a sound generator. Sound waves from the generator are applied to the container, causing it to vibrate. A vibration detector is used to determine the amount of container vibration. A preferred vibration detector involves a laser vibrometer which applies a reference laser beam to the vibrating container. The reference beam is reflected off of the container to generate a reflected laser beam. The reflected beam experiences a Doppler frequency shift compared with the reference beam which is caused by container vibration. The Doppler shift of the reflected beam is then compared with standardized Doppler shift data from a control container. Repeated Doppler shift measurements may also be undertaken which are converted into a vibration profile that is compared with a standardized vibration profile from a control container.