Method and device for rapid non-destructive quality control of powdered materials

Abstract

A method of non-destructive testing for quality control of powdered materials having dielectric properties based on the use of electromagnetic capacitance techniques.

1 . A method of non-destructive testing for quality control of powdered materials having dielectric properties, said method based on the use of electromagnetic capacitance techniques, and comprised of the following steps:
 switching on a generator of an electric field driving a transducer that is not in contact with a samples of the powder to be tested;   measurement of the self-capacitance and Q-factor of the resonance circuit with a capacitive sensor, which is located in the local ambient environment;   obtaining the computed operational parameters of said transducer electric circuit and sending them to the main unit for processing, storage, analysis and display;   switching off said generator of electric field for said transducer without sample powder;   positioning said sensor on the surface of the material to be tested, switching on an impulse generator to provide power for a vibrating electromagnetic transducer and/or immersing the sensor into the material to be tested;   shutting off of ultrasound generated for the vibrating electromagnetic transducer after the sensor has been fully immersed in the material to be tested;   switching on said generator of electric field for the transducer after said transducer has been fully immersed in the material to be tested;   measuring the phase shift caused by the effect of the powdered material being tested on the real and imaginary components of the impedance of said capacitance sensor;   measuring the frequency shift of the resonance circuit, containing said capacitive sensor, caused by the effect of the dielectric permeability of the powdered material upon the capacitance of said sensor;   determining capacitance of said sensor, which has been fully immersed in powdered material, by the value of the frequency shift;   determining the appropriate correcting signal for the phase shift;   determining the informative signal, which describes the magnitude of dielectric losses in the field of said sensor in contact with the powdered material to be tested;   transforming parameters of said sensor with powder in said electronic circuit of said sensor and sending them to the main unit for processing, storage, analysis and display;   removing the sensor from the powdered material being tested;   switching on the source of ultrasonic oscillation while removing the sensor from the powdered material to clean electrodes of the sensor of residual powder until the values of Q-factor of said resonance circuit, together with said capacitive sensor, reaches a predetermined threshold values;   making measuring from other areas on the surface of powdered materials and obtaining averages for all said measurements;   determining the of quality of the powdered material by taking the average of the informative signal value for all measurements.   
     
     
         2 . Method as in  claim 1 , wherein, the depth of immersion of said capacitive sensor into the powdered material is measured based on the capacitance value of the auxiliary capacitive sensor with the coplanar electrodes of the sensor being placed on the side surface of the working capacitive sensor case, wherein prior to immersion of said sensor, the source of ultrasonic vibrations is switched on. 
     
     
         3 . Method as in  claim 1 , wherein the correcting signal is measured by the capacitance value of a filled capacitive sensor, according to a calibration curve or look-up table of test measurement values, which have been previously made on a given type of powered material having different moisture contents. 
     
     
         4 . Method as in  claim 1 , wherein after said sensor is filled up with powdered material, said generator of electric field with a load is switched on according to the signal produced by an auxiliary sensor, and measurements are made of parameters of the transducer immersed in powdered material wherein the source of ultrasonic vibration is switched off during the measurement. 
     
     
         5 . Method as in  claim 1 , wherein the measuring transducer is taken out of powdered material and at the moment when the transducer lower end leaves the powder surface, the ultrasonic generator is switched on. 
     
     
         6 . Method as in  claim 1 , wherein the ultrasound vibration source remains switched on after the measurement of the Q-factor of the capacitive sensor has been made and the sensor has been removed from the powdered material, until the value of Q-factor comes up to the threshold level, after which then a signal is generated to switch off the ultrasonic vibration. 
     
     
         7 . Method as in  claim 1 , wherein the determining threshold value of the Q-factor of the capacitive sensor for the value of the Q-factor of the unloaded resonance circuit with a sensor is carried out wherein the unloaded Q-factor is obtained prior to first immersion of said sensor into powdered material and adjusted using a correction value in accordance with properties of the powder being tested. 
     
     
         8 . Method as in  claim 1 , wherein sensor circuit signal processing, storage, and analysis are carried out by an appropriate software program using the required algorithms to calculate the values of the informative parameters, and provide for their display on a suitable read-out device. 
     
     
         9 . Method as in  claim 1 , wherein the computed values of Q-factor, capacitances and for computed values of dielectric dissipation, relative change of Q-factor and/or dielectric permeability can be used as an informative parameters, the value of which indicate the quality of the powdered materials. 
     
     
         10 . Method as in  claim 1 , wherein the optimal frequency, which ensures the largest possible difference between informative signals from the sensors with and without the powder being tested, is selected and the source of the electric field for the working capacitance sensor is set to generate said optimal frequency. 
     
     
         11 - 18 . (canceled)