초록 ▼

Disclosed are apparatus and methods for detecting the presence, or absence, of material at a predetermined location. An oscillator generates a constant-frequency, constant-amplitude signal which is fed through a load resistor to an antenna probe positioned at the sensing location. The amplitude of t

Disclosed are apparatus and methods for detecting the presence, or absence, of material at a predetermined location. An oscillator generates a constant-frequency, constant-amplitude signal which is fed through a load resistor to an antenna probe positioned at the sensing location. The amplitude of the signal fed to the antenna probe varies as the impedance of the antenna probe is affected by material in its environment, or lack thereof. The signal amplitude is converted into a d-c voltage level, and is transmitted to a switching circuit which provides an output signal depending on a comparison between the d-c voltage level and a reference voltage level. The sensitivity of the switching circuit is adjustable to accommodate the degree to which the particular material, whose presence or absence is to be detected, affects the impedance of the antenna probe. The output from the switching circuit may be used to operate one or more devices indicative of the environment of the antenna probe and/or affecting the environment by adding to and/or removing therefrom material affecting the impedance of the antenna probe.

대표청구항 ▼

Apparatus for detecting the presence or absence of material at a location comprising: (a) signal generation means for providing an oscillatory signal; (b) antenna probe means for positioning at said location, and for receiving said oscillatory signal; (c) converter means for producing a voltage leve

Apparatus for detecting the presence or absence of material at a location comprising: (a) signal generation means for providing an oscillatory signal; (b) antenna probe means for positioning at said location, and for receiving said oscillatory signal; (c) converter means for producing a voltage level whose value is dependent on the amplitude of said oscillatory signal; (d) switching means, operable by said voltage level, for producing an output signal dependent on the presence or absence of material at said location; (e) comparator means, as part of said switching means, whose output controls said output signal depending on the value of said voltage level produced by said converter means compared to a reference voltage level; (f) sensitivity control means, for selectively adjusting the sensitivity of response of said switching means, including voltage selection means for selectively providing voltage levels to said switching means to selectively determine the value of said reference voltage level whereby the magnitude of the variation of said voltage levl, produced by said converter means, required to effect a change in said output signal is so selectively determined; and (g) said voltage selection means further comprising a voltage divider including a plurality of resistors, and sensitivity switch means for selectively communicating voltages from contacts between resistors in said voltage divider to said switching means to so selectively determine the value of said reference voltage level.