Method and apparatus for determining the content of unburnt coal in an ash from a combustion heater.

摘要

A method and an apparatus for determining the dielectric constant of a material (11) wherein the material is loaded to a short-circuited microstrip (10) and microwaves are fed to the microstrip for providing a reflected signal (V4). The reflected signal is compared with a reference signal (V,) both under load and not load conditions of the microstrip for obtaining the modulus and the phase of the reflection coefficient, the dielectric constant being a function thereof. The measure of the phase angle between the reference and the reflected signal in both conditions is obtained by handling the reflected signal with a first phase shifter (6) and a second calibrated phase shifter (7) cooperating with a zero detector (4). The method and the apparatus of the invention is especially designed for a quick and easy measure of the amount of unburnt coal in the ash coming from a combustion heater.