Method of measuring moisture content of dielectric materials

Claim 1

A method of measuring the moisture content of a moisture-containing dielectric material by capacitively coupling it into at least one bridge circuit and measuring the bridge unbalance when an alternating current input having superposed frequencies is applied across each bridge circuit, the improvement which comprises: a. applying n superposed alternating current frequencies to the bridge, where n is a whole number equal to or greater than 2; b. determining the bridge unbalance caused at each frequency and converting it into a direct current voltage signal; c. measuring the temperature of the material; and d. computing the moisture content by entering the voltage signals and temperature into an algorithm having the form: ##EQU4## where MC is moisture content, A 0 (T), B i (T), and C ij (T) are all polynominal functions of temperature n is a whole number equal to or greater than 2, and V i and V j are the direct current amplitudes of the ith and jth frequency components.

Claim 2

A method of measuring the moisture content of a moisture-containing dielectric material by capacitively coupling it into at least one bridge circuit and measuring the bridge unbalance when an alternating current input having superposed frequencies is applied across each bridge circuit, the improvement which comprises: a. applying n superposed alternating current frequencies to the bridge, where n is a whole number equal to or greater than 2; b. determining the bridge unbalance caused at each frequency and converting it into a direct current voltage signal; c. measuring the temperature of the material; and d. computing the moisture content by entering the voltage signals and temperature into an algorithm having the form: ##EQU4## where MC is moisture content, A 0 (T), B i (T), and C ij (T) are all polynominal functions of temperature n is a whole number equal to or greater than 2, and V i and V j are the direct current amplitudes of the ith and jth frequency components.

Claim 4

The method of claims 1 or 2 in which the lowest and highest frequencies differ at least by one power of 10.

Claim 7

The method of claims 1 or 2 in which the moisture content is corrected for the particular characteristics of the dielectric material by entering the uncorrected value into the algorithm MC.sub.corr =k.sub.1 +k.sub.2 MC where k 1 and k 2 are coefficients unique to the dielectric material being measured.

Claim 9

The method of claims 1 or 2 including providing two bridge circuits in a balanced push pull arrangement each bridge circuit having a sensing electrode in parallel with a capacitor in one leg of the bridge circuit, each electrode having an adjacent zone within which it is effectively capacitively coupled to the material being measured.

Claim 21

The method of claims 17 or 18 which includes providing a computer which receives inputs of bridge unbalance voltage and temperature and solves the algorithm to indicate a moisture content.

Claim 22

The method of claims 17 or 18 in which the lowest and highest frequencies differ at least by one power of 10.

Claim 25

The method of claims 17 or 18 in which the moisture content is corrected for the particular characteristics of the dielectric material by entering the uncorrected value into the algorithm MC.sub.corr =k.sub.1 +k.sub.2 MC where k 1 and k 2 are coefficients unqiue to the dielectric material being measured.

Claim 27

The method of claims 17 or 18 including providing two bridge circuits in a balanced push pull arrangement each bridge circuit having a sensing electrode in parallel with a capacitor in one leg of the bridge circuit, each electrode having an adjacent zone within which it is effectively capacitively coupled to the material being measured.

Claim 36

A method of measuring the moisture content of moisture containing dielectric material which comprises: a. providing at least one pair of electrodes in a coupled relationship with the material; b. driving the electrodes with an alternating current signal comprising two superposed frequencies so that opposite electrodes of a pair are at essentially equal voltages of opposite polarity, each electrode being located in an arm of separate bridge circuits; c. sensing the unbalance signals in the bridge circuits caused by the presence of the material adjacent to the electrodes, said signals containing components of unbalance at each frequency; d. combining the unbalance signals from the two bridges; e. separating the combined signal into its individual frequency components and rectifying each component to form direct current voltage signals proportional to the bridge unbalance caused at each frequency; f. sensing the temperature of the dielectric materials; and g. computing the moisture content by entering the voltage signals and the temperature into an algorithm having the form MC=a+bV.sub.1 +cV.sub.2 +dV.sub.1 V.sub.2 where MC is moisture content, V 1 and V 2 are the direct current voltage signals, and the coefficients are temperature-dependent according to the relationships ##EQU6## with m being a whole number equal to or greater than 1.

Claim 37

A method of measuring the moisture content of moisture containing dielectric material which comprises: a. providing at least one pair of electrodes in a coupled relationship with the material; b. driving the electrodes with an alternating current signal comprising two superposed frequencies so that opposite electrodes of a pair are at essentially equal voltages of opposite polarity, each electrode being located in an arm of separate bridge circuits; c. sensing the unbalance signals in the bridge circuits caused by the presence of the material adjacent to the electrodes, said signals containing components of unbalance at each frequency; d. combining the unbalance signals from the two bridges; e. separating the combined signal into its individual frequency components and rectifying each component to form direct current voltage signals proportional to the bridge unbalance caused at each frequency; f. sensing the temperature of the dielectric materials; and g. computing the moisture content by entering the voltage signals and the temperature into an algorithm having the form MC=a+bV.sub.1 +cV.sub.2 +dV.sub.1 V.sub.2 where MC is moisture content, V 1 and V 2 are the direct current voltage signals, and the coefficients are temperature-dependent according to the relationships ##EQU6## with m being a whole number equal to or greater than 1.

Claim 39

The method of claims 34 or 35 which includes providing a computer which receives inputs of bridge unbalance voltage and temperature and solves the algorithm to indicate a moisture content.

Claim 40

The method of claims 34 or 35 in which the lowest and highest frequencies differ at least by one power of 10.

Claim 43

The method of claims 34 or 35 in which the moisture content is corrected for the particular characteristics of the dielectric material by entering the uncorrected value into the algorithm MC.sub.corr =k.sub.1 +k.sub.2 MC where k 1 and k 2 are coefficients unique to the dielectric material being measured.

Claim 45

The method of claims 34 or 35 including providing two bridge circuits in a balanced push pull arrangement each bridge circuit having a sensing electrode in parallel with a capacitor in one leg of the bridge circuit, each electrode having an adjacent zone within which it is effectively capacitively coupled to the material being measured.

Claim 51

The method of claims 45 or 46 which further includes material detection means following the measuring heads to indicate when the material has moved out of the zone in which it is effectively coupled to the heads.