Apparatus and method for monitoring the presence of a conductive media

Claim 2

In a conductive media detecting apparatus of the type in which primary and secondary windings are inductively coupled together and the presence of and the proportion thereof immersed in surrounding liquid metal varies the coupling and hence mutual inductance parameter between said coils, the improvement in combination therewith of: means for exciting said primary winding with an AC signal of substantially constant current and selectively settable frequency f to induce an AC voltage signal of frequency f on said secondary winding; and, means responsive to said induced voltage signal for generating an output signal which is a measure of the presence of a conductive media being monitored, said output signal generating means being operable to generate said output signal as a function of the product of the magnitude of said induced voltage signal and the cosine of the angle of phase difference between said constant current signal and induced voltage signal.

Claim 3

In a conductive media detecting apparatus of the type in which primary and secondary windings are inductively coupled together and the presence of and the proportion thereof immersed in surrounding liquid metal varies the coupling and hence mutual inductance parameter between said coils, the improvement in combination therewith of: means for exciting said primary winding with an AC signal of substantially constant current and selectively settable frequency f to induce an AC voltage signal of frequency f on said secondary winding; means responsive to said induced voltage signal for generating an output signal which is a measure of the presence of a conductive media being monitored, said output signal generating means being operable to generate said output signal as a function of the product of the magnitude of said induced voltage signal and the cosine of the angle of phase difference between said constant current signal and induced voltage signal; the angular phase difference between said constant current and induced voltage signals varies as a function of the inductive coupling of said windings and is designated φ; the magnitude of said induced voltage signal is |V|; the output signal generated by said output signal generating means is directly proportional to |V| cos (φ-θ), where θ is a phase shift factor which may be selectively set; and, said means for exciting said primary winding with said constant current signal includes a frequency adjustable oscillator operable to generate an AC signal at said frequency f and a constant current regulator operable to generate from said oscillator AC signal said constant current signal.

Claim 4

In a conductive media detecting apparatus of the type in which primary and secondary windings are inductively coupled together and the presence of and the proportion thereof immersed in surrounding liquid metal varies the coupling and hence mutual inductance parameter between said coils, the improvement in combination therewith of: means for exciting said primary winding with an AC signal of substantially constant current and selectively settable frequency f to induce an AC voltage signal of frequency f on said secondary winding; means responsive to said induced voltage signal for generating an output signal which is a measure of the presence of a conductive media being monitored, said output signal generating means being operable to generate said output signal as a function of the product of the magnitude of said induced voltage signal and the cosine of the angle of phase difference between said constant current signal and induced voltage signal; the angular phase difference between said constant current and induced voltage signals varies as a function of the inductive coupling of said windings and is designated φ; the magnitude of said induced voltage signal is |V|; the output signal generated by said output signal generating means is directly proportional to |V| cos (φ-θ), where θ is a phase shift factor which may be selectively set; and, said means for exciting said primary winding with said constant current signal includes a frequency adjustable oscillator operable to generate an AC signal at said frequency f and a constant current regulator operable to generate from said oscillator AC signal said constant current signal.

Claim 5

In a conductive media detecting apparatus of the type in which primary and secondary windings are inductively coupled together and the presence of surrounding liquid metal varies the coupling and hence mutual inductance parameter between said coils, the improvement in combination therewith of: means for exciting said primary winding with an AC signal of substantially constant current and selectively settable frequency f to induce an AC voltage signal of frequency f on said secondary winding; means responsive to said induced voltage signal for generating an output signal which is a measure of the presence of a conductive media being monitored, said output generating means being operable to generate said output signal as a function of the product of the magnitude of said induced voltage signal and the cosine of the angle of phase difference between said constant current signal and induced voltage signal; the angular phase difference between said constant current and induced voltage signals varies as a function of the inductive coupling of said windings and is designated φ; the magnitude of said induced voltage signal is |V|; the output signal generated by said output signal generating means is directly proportional to |V| cos (φ-θ), is a phase shift factor which may selectively set; said means for exciting said primary winding with said constant current signal includes a frequency adjustable oscillator operable to generate an AC signal at said frequency f and a constant current regulator operable to generate from said oscillator AC signal said constant current signal; said means for exciting said primary winding with said constant current signal includes means responsive to said oscillator AC signal to generate a clock signal at frequency f substantially in phase with said constant current signal; and, said output signal generating means includes selectively settable means responsive to said clock signal for generating a reference signal shifted in phase said selected phase angle θ from said constant current signal and means responsive to said induced voltage and reference signals for generating a signal proportional to said product of |V| cos (φ-θ).

Claim 6

In a conductive media detecting apparatus of the type in which primary and secondary windings are inductively coupled together and the presence of surrounding liquid metal varies the coupling and hence mutual inductance parameter between said coils, the improvement in combination therewith of: means for exciting said primary winding with an AC signal of substantially constant current and selectively settable frequency f to induce an AC voltage signal of frequency f on said secondary winding; means responsive to said induced voltage signal for generating an output signal which is a measure of the presence of a conductive media being monitored, said output generating means being operable to generate said output signal as a function of the product of the magnitude of said induced voltage signal and the cosine of the angle of phase difference between said constant current signal and induced voltage signal; the angular phase difference between said constant current and induced voltage signals varies as a function of the inductive coupling of said windings and is designated φ; the magnitude of said induced voltage signal is |V|; the output signal generated by said output signal generating means is directly proportional to |V| cos (φ-θ), is a phase shift factor which may selectively set; said means for exciting said primary winding with said constant current signal includes a frequency adjustable oscillator operable to generate an AC signal at said frequency f and a constant current regulator operable to generate from said oscillator AC signal said constant current signal; said means for exciting said primary winding with said constant current signal includes means responsive to said oscillator AC signal to generate a clock signal at frequency f substantially in phase with said constant current signal; and, said output signal generating means includes selectively settable means responsive to said clock signal for generating a reference signal shifted in phase said selected phase angle θ from said constant current signal and means responsive to said induced voltage and reference signals for generating a signal proportional to said product of |V| cos (φ-θ).

Claim 7

The invention defined in claim 3, including means for calibrating said output signal generating means.

Claim 8

The invention defined in claim 4, wherein: said calibrating means is responsive to said oscillator AC signal and is operable to generate therefrom a first signal corresponding in magnitude and phase to said induced voltage signal at full level and a second voltage signal corresponding in magnitude and phase to said induced voltage signal at zero level; and, including: switch means for selectively supplying either said induced voltage signal, said first calibration signal or said second calibration signal to said output signal generating means; and, wherein: said output signal generating means includes circuitry for adjusting its maximum output to correspond to said first calibration signal and its minimum output to correspond to said second calibration signal.

Claim 9

The invention defined in claim 5, wherein said primary and secondary windings form an inductive probe having a longitudinal axis which is positioned normal to the surface of a conductive media to be monitored.

Claim 10

The invention defined in claim 5, wherein said primary and secondary windings are each bifilar coils.

Claim 11

The invention defined in claim 7, including means for converting said output signal into both voltage and current signals which are a measure of the level of the liquid metal being monitored.

Claim 12

The invention defined in claim 3, wherein said primary and secondary windings form an inductive probe having a longitudinal axis which is positioned normal to the level of a pool of liquid metal to be monitored.

Claim 15

The method of claim 10, wherein: the angular phase difference between said constant current and induced voltage signals varies as a function of the inductive coupling of said windings and is designated φ; the magnitude of said induced voltage signal is |V|; and, said output signal generated is directly proportional to |V| cos (φ-θ) where θ is a phase shift factor which may be selectively set; and including the steps of: concurrently adjusting the frequency f and phase shift factor θ to minimize variations caused in said output signal by temperature effects.