초록 ▼

Disclosed are apparatus and methods for detecting the extent to which material is present at a predetermined sensing area. An antenna probe is extended throughout the sensing area, and is loaded with a signal from an oscillator. A reference oscillator provides a constant-frequency signal of the same

Disclosed are apparatus and methods for detecting the extent to which material is present at a predetermined sensing area. An antenna probe is extended throughout the sensing area, and is loaded with a signal from an oscillator. A reference oscillator provides a constant-frequency signal of the same base frequency as the antenna oscillator signal. The presence of impedance-affecting material in the sensing area reduces the impedance load of the antenna and, therefore, the frequency of the output signal of the antenna oscillator in proportion to the extent of immersion of the antenna probe in such material. The output signals from both oscillators are compared in a frequency differencer circuit which produces output signals whose frequency, equal to the difference in frequencies of the two oscillator output signals, is an indication of the amount of material present in the sensing area. A testing circuit provides an indication of the frequency of the differencer output signal, and is used in adjusting the sensitivity of the detector circuitry with the antenna probe free of impedance-affecting material. With the oscillator sensitivities adjusted, the detector circuitry is zeroed, again with reliance on the testing circuit to indicate when both oscillators are generating the same output frequency. The differencer output signals may be converted to voltage levels proportional to the extent material is present at the antenna probe. Such voltage levels may be used, ultimately, to operate one or more devices to indicate the amount of material present in the sensing area and/or to control the amount of material in the sensing area.

대표청구항 ▼

Apparatus for measuring a variable quality or quantity of matter present within a sensing area comprising: (a) signal generation means including first oscillator means for providing an oscillatory signal, and including sensitivity control means for selectively adjusting the sensitivity of said signa

Apparatus for measuring a variable quality or quantity of matter present within a sensing area comprising: (a) signal generation means including first oscillator means for providing an oscillatory signal, and including sensitivity control means for selectively adjusting the sensitivity of said signal generation means; (b) antenna probe means, as part of said signal generation means, for extending in said sensing area and for receiving said oscillatory signal whereby the frequency of said oscillatory signal is varied in accordance with the modification of impedance of said antenna probe means due to the exposure of said antenna probe means to matter within said sensing area; (c) electrical processing means for receiving said oscillatory signal and for producing an output signal whose frequency varies as the extent of the antenna probe means so exposed to material within said sensing area; and (d) test circuit means, as part of said electrical processing means, for receiving said output signal and providing a test output indicative of the value of said output signal frequency, including (i) counter means for receiving said output signal and for providing, as said test output, counter signals, initiated in sequence, of frequencies that are, progressively, smaller fractional multiples of the frequency of the output signal, wherein a zero output signal frequency results in no oscillatory counter signals being provided; (ii) indicator means for separately signaling the production of each such counter signal; and (iii) timing means for periodically providing a reset signal to said counter means to define a time span during which said counter means may so produce said counter signals in sequence, said counter means thereafter initiating a subsequent time span for producing counter signals.