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US 4,069,710 AGranted
Apparatus for the capacitative measurement of the surface level of fluid media in vessels
OwnerOtto Treierinventor
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OwnerOtto Treierinventor
Estimating the term…
Apparatus for the capacitative measurement of the surface level of a fluid medium in a vessel comprises a probe mounted to provide a capacitance between itself and the surface, the probe being connected into one of two RC-circuits, respectively connected to opposite ends of a secondary winding of a transmitter, the primary winding of which is in a resonant high-frequency generator circuit. The two RC-circuits are earthed and respectively connected through rectifiers to the inputs of a differential amplifier, the output of which provides an output signal corresponding to the capacitance between the probe and surface level. The RC-circuit associated with the probe comprises a parallel manually adjustable capacitor and a capacitance diode arranged for the remote adjustment of the RC-circuit. Where there is a substantial separation of the probe from the RC-circuits a two-core high-frequency cable is used with one core connecting the probe into the associated RC-circuit and the other core connecting an insulated point on the probe to the other RC-circuit. A simple, sensitive apparatus, unaffected by temperature variations is thereby provided.
Apparatus for the measurement of the surface level of a fluid medium in a vessel, comprising a vessel, a high-frequency electrical generator, a high-frequency transmitter having inductively coupled primary and secondary portions, means connecting said generator and said transmitter for the supply of high frequency electric current to said primary portion, first and second terminal connectors with said secondary portion connected therebetween to provide a high-frequency induced current between said terminal connectors, a first capacitor, means earthing said first terminal connector by way of said first capacitor, a probe mounted on said vessel to provide a second capacitor providing a capacitance between said probe and fluid medium in said vessel, said capacitance depending on the surface level of fluid medium in said vessel, means earthing said second terminal connector by way of said second capacitor, rectifier means, and means connecting said rectifier means to said first and second capacitors for the rectification of alternating voltages present on said capacitors, thereby providing direct-current voltage outputs respectively from said first and second capacitors, and means having two inputs respectively connected to receive said voltage outputs and itself providing an output corresponding to said capacitance and, therefore, to said surface level.
Apparatus according to claim 14, in which said further capacitor is a manually adjustable capacitor.
Dependencies are inferred from the claim text.