Radio frequency measuring apparatus
First Claim
1. A device for measuring a composition of a material comprising:
- a pair of electrodes immersed in the material to be measured which are switchably coupled to the tank circuit of a variable frequency oscillator operating at radio frequencies through means for reducing damping of the tank circuit;
additional capacitance or inductance switchably introduced to modify the frequency of the tank circuit to thereby form two frequencies which are measured with the electrodes connected to the oscillator, whereby errors due to oscillator drift are minimized by intermittently taking a succession of frequency measurements followed by reference frequencies with the electrodes disconnected from the oscillator, a time difference between frequency measurements being of the order of seconds; and
means for computing the differences between the measured and reference frequencies and using these differences to derive at least one signal representative of the composition of the material being measured.
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Accused Products
Abstract
A device is provided for measuring dielectric constant and conductance of a material such as massecuite, the device including a pair of electrodes which are switchably connected to a tank circuit which includes a variable frequency oscillator operating at radio frequencies, and two reference frequencies are measured with the electrodes disconnected from the oscillator and two measurement frequencies with the electrodes coupled to the oscillator tank circuit, the differences between the reference and measurement frequencies being used to compute the inductance and dielectric constant or composition of the material. The frequency is modified by not more than about 10 MHz and may be achieved either by switchably introducing additional inductance or capacitance into the tank circuit to modify its frequency or by having the electrodes switchable between a pair or oscillators operating at known radio frequencies.
26 Citations
6 Claims
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1. A device for measuring a composition of a material comprising:
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a pair of electrodes immersed in the material to be measured which are switchably coupled to the tank circuit of a variable frequency oscillator operating at radio frequencies through means for reducing damping of the tank circuit; additional capacitance or inductance switchably introduced to modify the frequency of the tank circuit to thereby form two frequencies which are measured with the electrodes connected to the oscillator, whereby errors due to oscillator drift are minimized by intermittently taking a succession of frequency measurements followed by reference frequencies with the electrodes disconnected from the oscillator, a time difference between frequency measurements being of the order of seconds; and means for computing the differences between the measured and reference frequencies and using these differences to derive at least one signal representative of the composition of the material being measured. - View Dependent Claims (2, 3, 4)
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5. A device for measuring a composition of a material comprising:
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a pair of electrodes immersed in a material to be measured which are switchably coupled to tank circuits of two variable frequency oscillators; means for reducing damping of the tank circuits; means for measuring two frequencies with the electrodes connected to the oscillator, errors due to drift of the oscillators being minimized by intermittently taking a succession of frequency measurements followed by reference frequencies with the electrodes disconnected from the oscillator, the time differences between frequency measurements being of the order of seconds; means for calibrating the device against materials of known compositions; and means for computing a difference between the measured and reference frequencies to produce at least one signal representative of the composition of the material being measured. - View Dependent Claims (6)
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Specification