| 摘要 |
A storage installation capable of storing a variety of materials includes a shielded level sensing device disposed entirely externally of the container. The sensing device includes an elongated strip of metal which is associated with shielding circuitry for electrostatic protection of the strip. The sensing metal strip serves as a capacitor component in an oscillator circuit which is arranged so that the electrostatic field emanating from the sensing strip will change oscillator amplitude in proportion to the level to be sensed of material in the container. Detected changes in amplitude of the oscillator circuit produce a DC level proportional to the level of the oscillator amplitude, which in turn may be processed to indicate the level of material within the storage container. Either a grounded fine wire mesh or a plurality of commonly grounded parallel conducting wires situated externally to a foam insulating block associated with the elongated metal sensing strip serves as an electrostatic shield about such strip for the exclusion of external electrostatic influences. The resulting electrostatic field confinement results in improved reliability for level sensing.
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