Transforming sensor for contact-free determination of filling state and conductivity of conductive medium in non-conductive container, is based on damping of oscillating circuit obtained using sensor coil

摘要

A transforming sensor comprises an active sensor coil (1), located close to a non-conductive wall (2) of a container for a conductive liquid medium (4), which is a component of an oscillating circuit producing alternating magnetic flux (5) in the medium. The flux penetrates the medium and creates a circuit of current (6) which damps the oscillating circuit. The oscillation amplitude reduction is a measure of the conductivity and an indication of the presence of the medium. A transforming sensor comprises an active sensor coil (1) located with its flat side close to a non-conductive or non-metallic wall (2) of a container for a conductive liquid, gel or paste medium (4). The sensor coil is a component of an inductance-capacitance (LC) oscillating circuit and a freely oscillating circuit, which maintains an oscilllation in the oscillating circuit so that the coil produces an alternating magnetic flux (5) in the medium. The flux penetrates perpendicularly into the medium and (due to the conductivity of the medium) creates a circuit (6) of weak, alternating or eddy current. This current (in combination with a potential difference due to the ohmic resistance characteristic of the conductivity of the medium) produces an active output, which (due to transformatory coupling of the coil with the medium) depletes the oscillation circuit so that the circuit undergoes damping. The amplitude of the high frequency (HF) oscillation of the oscillation circuit is thus markedly reduced, and the reduction is both a direct measure of the conductivity of the medium and an indication of the presence of the medium. An independent claim is included for a corresponding method of filling state evaluation or conductivity analysis using the sensor.