Frieder Lucklum, Bernhard Jakoby,
"Principle of a Non-contact Liquid Level Sensor Using Electromagnetic-Acoustic Resonators"
, in OVE, in e&i Elektrotechnik und Informationstechnik, Vol. 126, Nummer 1-2, Springer Verlag, Seite(n) 3-7, 2-2009, ISSN: 0932-383X
Principle of a Non-contact Liquid Level Sensor Using Electromagnetic-Acoustic Resonators
Sprache des Titels:
Liquid level measurement is a key aspect for many applications in the processing industry, chemistry, and pharmaceutical industry to determine, e.g., the exact liquid volume in a reaction chamber. A large variety of measurement principles exist for these applications, ranging from mechanical, electrical, and optical methods to ultrasonic and radar measurements. However, many of these principles are not suitable for sensing very small amounts of liquid volume and liquid levels. Ultrasonic transducers allow for very precise measurements, where the sensitivity can be improved by increasing the operating frequency. In this contribution we introduce the concept of electromagnetic-acoustic resonators as the ultrasonic transducer. Here, we measure the changed frequency shifts and damping characteristics due to interference effects instead of the time-of-flight measurements usually employed. Our experiments show, that by using continuous, resonant excitation the achievable resolution is not limited by the wavelengths of the ultrasonic waves radiated into the liquid. We introduce an experimental setup consisting of a simple resonating element placed inside the fluidic chamber, which is remotely excited by a planar coil. We present an analytical model for the operation of these devices based on finite element simulations of the excited resonant mode shapes. The ability of electromagnetic-acoustic excitation to easily generate many different modes of vibration is also an advantage to simultaneously measure liquid level and other liquid properties.
Sprache der Kurzfassung:
e&i Elektrotechnik und Informationstechnik
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