Absolute property measurement with air calibration

A sensor comprising:

• a primary winding meandering in a back and forth square wave-like pattern and having a plurality of parallel legs, a half wave length defined by the space between a pair of adjacent parallel legs;
• a plurality of sensing elements, the sensing elements interposed between the legs of the primary winding;
• and
• a gap between the sensing element and the parallel legs of the primary winding is approximately an eighth of a wavelength for minimizing coupling of shorter wavelength modes.

An instrument for measuring property of a material comprising

• a sensor having
• a primary winding meandering in a square wave pattern and having a plurality of parallel legs, a half wave length defined by the space between a pair of adjacent parallel legs;
• and
• a plurality of sensing elements, the sensing elements interposed between the legs of the primary winding;
• a probe head for holding the sensor;
• an impedance analyzer for inputting an input current or voltage source at a temporal excitation frequency and measuring the output from the sensing elements, the analyzer having remote analog components;
• and
• a property analyzer for analysis of the measured output.

A method of calibration of a sensor comprising the following steps:

• providing a sensor having a primary winding meandering in a square wave pattern with a plurality of parallel legs and a plurality of sensing elements with the sensing elements interposed between the legs of the primary winding;
• connecting the sensor to an impedance analyzer;
• placing the sensor in the air away from a material under test;
• introducing a current into the primary winding;
• measuring the voltage resulting on the sensing elements using the impedance analyzer;
• and
• aligning the phase and magnitude of the impedance to a measurement grid.

A method of measuring a property of a material comprising the following steps:

• providing a sensor having a primary winding meandering in a square wave pattern with a plurality of parallel legs and a plurality of sensing elements with the sensing elements interposed between the legs of the primary winding;
• connecting the sensor to an impedance analyzer;
• placing the sensor in the air away from a material under test;
• introducing a current into the primary winding;
• measuring the voltage resulting on the sensing elements using the impedance analyzer;
• aligning the phase and magnitude of the impedance to a measurement grid;
• moving the sensor in proximity to the material under test;
• introducing a current into the primary winding;
• measuring the voltage resulting on the sensing elements using the impedance analyzer;
• and
• converting the phase and magnitude of the impedance using the measurement grid to determine at least one unknown property of interest.

A method of measuring a property of a material comprising the following steps:

• providing a sensor having a primary winding meandering in a square wave pattern with a plurality of parallel legs and a plurality of sensing elements with the sensing elements interposed between the legs of the primary winding, wherein the sensor elements opening to one side of the primary winding are connected in a plurality of distinct groups and sensing elements opening to the other side of the primary winding are connected in a plurality of distinct groups and each of the groups of the one side having at least one sensing element located interposed between sensing elements of a group on the other side and at least one sensing element located interposed between sensing elements of a second group on the other side, therein the groups overlapping;
• connecting the sensor to an impedance analyzer;
• moving the sensor in proximity to a material under test;
• introducing a current into the primary winding;
• measuring the voltage resulting on the sensing elements using the impedance analyzer;
• and
• converting the phase and magnitude of the impedance using the measurement grid to determine at least one unknown property of interest.

A method of measuring a property of a material comprising the following steps:

• providing a sensor having a primary winding meandering in a square wave pattern with a plurality of parallel legs and a plurality of sensing elements with the sensing elements interposed between the legs of the primary winding, wherein the sensor elements opening to one side of the primary winding are connected in a plurality of distinct groups and sensing elements opening to the other side of the primary winding are connected in a plurality of distinct groups and at least one group on the one side has less sensing elements that the at least one group on the other side and all the sensing elements of the one group on the one side are interposed between sensing elements of the one group of the other side;
• connecting the sensor to an impedance analyzer;
• moving the sensor in proximity to a material under test;
• introducing a current into the primary winding;
• measuring the voltage resulting on the sensing elements using the impedance analyzer;
• and
• converting the phase and magnitude of the impedance using the measurement grid to determine at least one unknown property of interest.

A method of measuring a property of a material comprising the following steps:

• providing a sensor having a primary winding meandering in a square wave pattern with a plurality of parallel legs and a plurality of sensing elements with the sensing elements interposed between the legs of the primary winding;
• connecting the sensor to an impedance analyzer;
• moving the sensor in proximity to a material under test;
• introducing a current into the primary winding;
• measuring the voltage resulting on the sensing elements using the impedance analyzer;
• and
• converting the phase and magnitude of the impedance using a measurement grid wherein all the sensing elements are grouped together for absolute measurements.

A method of measuring a property of a material comprising the following steps:

• providing a sensor having a primary winding meandering in a square wave pattern with a plurality of parallel legs and a plurality of sensing elements with the sensing elements interposed between the legs of the primary winding;
• connecting the sensor to an impedance analyzer;
• moving the sensor in proximity to a material under test;
• introducing a current into the primary winding;
• measuring the voltage resulting on the sensing elements using the impedance analyzer;
• and
• converting the phase and magnitude of the impedance using a measurement grid of at least one sensing element to determine the absolute measurement of at least one property and measuring the differences between sensing elements to increase the sensitivity to at least one unknown property.