Meter and method for in situ measurement of the electromagnetic

Abstract

An apparatus and method for the measurement of, for example, the moisture in a material or, more generally, for the measurement of any material parameter which may be inferred by measuring the electromagnetic properties of the material under investigation. The meter apparatus comprises a controllable source of electromagnetic energy having stable selectable frequency. The controllable source of electromagnetic energy is coupled to a material measurement chamber by means of probes, loops, antennas, apertures or other structures so as to establish an electromagnetic field inside the measurement chamber thereby causing the field to interact with the material contained in the chamber. The method includes passing the process material through a frequency sensitive measurement cell. Exposing the process material to electromagnetic energy produced by a multi-frequency source. Generating an output signal having a distinctive frequency response characteristic. Detecting and amplifying an output signal by a receiving means and converting the signal to a digital representation. Analyzing the digital representation of the signal by the computer to determine the cutoff frequency. Determining the sharpness of the cutoff characteristic by mathematical algorithms in the computer. From the measured cutoff frequency and the sharpness of the cutoff characteristic, determining the dielectric constant and the conductivity of the material. Using stored calibration data or equations in the computer, computing and displaying the desired material property, e.g., the material's moisture content. And further, using the passband attenuation to determine the density of the material.