Micropower RF material proximity sensor
First Claim
1. An apparatus for detecting a proximity of a material, comprising:
- an oscillator which oscillates at a nominal frequency and produces an oscillator signal;
an antenna coupled to the oscillator which is resonant at the nominal frequency of the oscillator and which has a characteristic impedance which depends on materials in proximity to the antenna; and
a detector coupled to the oscillator which detects changes in the oscillator signal as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna.
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0 Petitions
Accused Products
Abstract
A level detector or proximity detector for materials capable of sensing through plastic container walls or encapsulating materials is of the sensor. Thus, it can be used in corrosive environments, as well as in a wide variety of applications. An antenna has a characteristic impedance which depends on the materials in proximity to the antenna. An RF oscillator, which includes the antenna and is based on a single transistor in a Colpitt'"'"'s configuration, produces an oscillating signal. A detector is coupled to the oscillator which signals changes in the oscillating signal caused by changes in the materials in proximity to the antenna. The oscillator is turned on and off at a pulse repetition frequency with a low duty cycle to conserve power. The antenna consists of a straight monopole about one-quarter wavelength long at the nominal frequency of the oscillator. The antenna may be horizontally disposed on a container and very accurately detects the fill level within the container as the material inside the container reaches the level of the antenna.
104 Citations
41 Claims
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1. An apparatus for detecting a proximity of a material, comprising:
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an oscillator which oscillates at a nominal frequency and produces an oscillator signal; an antenna coupled to the oscillator which is resonant at the nominal frequency of the oscillator and which has a characteristic impedance which depends on materials in proximity to the antenna; and a detector coupled to the oscillator which detects changes in the oscillator signal as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for detecting a level of material in a container, comprising:
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an oscillator which oscillates at a nominal frequency and produces an oscillator signal; an antenna coupled to the oscillator which is resonant at the nominal frequency of the oscillator and which has a characteristic impedance which depends on proximity of the material in the container to the antenna; and a detector coupled to the oscillator which detects changes in the oscillator signal as a result of changes in the characteristic impedance of the antenna caused by proximity to the antenna of the material in the container. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. An apparatus for detecting a proximity of a material, comprising:
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an antenna which is resonant at a nominal frequency and has a characteristic impedance which depends on proximity to the antenna of the material; a transistor having a first terminal coupled to the antenna to provide theretogether a radio frequency resonant circuit which oscillates at the nominal frequency at which the antenna is resonant with an amplitude dependent on the characteristic impedance of the antenna, a second terminal receiving a bias potential and a third terminal; a detector coupled to the transistor which detects changes in the oscillation of the resonant circuit as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna; and a control circuit coupled to the third terminal of the transistor which turns the transistor on and off with a duty cycle to produce a sequence of bursts of oscillations at the nominal frequency. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
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35. A method for detecting proximity of a material to a particular location, comprising:
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placing an antenna having a characteristic impedance which depends on materials in proximity to the antenna in the particular location; establishing a resonating signal at a nominal frequency in the antenna; and detecting changes in the resonating signal at the nominal frequency as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna. - View Dependent Claims (36, 37, 38, 39, 40, 41)
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Specification