Measurement of amount of solid in suspension

1. A device for measuring the amount of solid in a suspension, the device comprising:

a first measuring part configured to direct electromagnetic radiation to the suspension and to measure the electromagnetic radiation interacted with the suspension in order to measure the amount of the dispersed matter in the suspension, the suspension including a liquid medium and solid particles and gas dispersed therein;

a second measuring part configured to measure at least one electrical conductivity and impedance distribution in the suspension impedance tomographically in order to determine a proportional volume of a free gas contained in the suspension; and

a signal processing part configured to form one or more cross-sectional views from the suspension and provide the amount of solid matter dispersed in the suspension on the basis of the amount of the dispersed matter and the proportional volume of the free gas in the one or more cross-sectional views formed from the suspension.

2. The device of claim 1 , wherein, in addition to the proportional volume, the second measuring part is configured to determine on the free gas at least one of the amount of bubbles and the amount of interfaces between the bubbles and the suspension.

3. The device of claim 1 , wherein the signal processing part is configured to determine the proportional total amount of the solid matter and the gas on the basis of electromagnetic radiation measurement,

the signal processing part is configured to determine the proportional volume of free gas in the suspension based on at least one of the electrical conductivity and the impedance distribution, and

the signal processing part is configured to subtract the determined proportional volume of free gas from the determined proportional total amount of the solid matter and the gas.

4. The device of claim 1 , wherein the first measuring part is configured to measure the transit time of radio-frequency electromagnetic radiation.

5. The device of claim 1 , wherein the first measuring part is configured to measure attenuation of optical electromagnetic radiation.

6. A method for measuring the amount of solid in a suspension, the method comprising:

measuring the amount of solid dispersed in the suspension in a measurement, in which electromagnetic radiation interacts with the suspension, the suspension including a liquid medium and solid particles and gas dispersed therein;

measuring a proportional volume of a free gas contained in the suspension on the basis of impedance tomographical measurement of at least one of electrical conductivity and impedance distribution in the suspension; and

forming one or more cross-sectional views from the suspension and providing the amount of solid matter dispersed in the suspension on the basis of the amount of the dispersed matter and the proportional volume of the free gas in the one or more cross-sectional views formed from the suspension.

7. The method of claim 6 , the method further comprising:

measuring the electromagnetic radiation that has interacted with the suspension and determining the proportional total amount of the solid matter and the gas on the basis of said electromagnetic radiation measurement;

determining the proportional volume of free gas in the suspension based on at least one of the electrical conductivity and the impedance distribution; and

subtracting the determined proportional volume of free gas from the determined proportional total amount of the solid matter and the gas.

8. The method of claim 6 , the method further comprising measuring the transit time of the radio-frequency electromagnetic radiation in order to determine the amount of the dispersed matter in the suspension.

9. The method of claim 6 , the method further comprising measuring the attenuation of the optical electromagnetic radiation in order to determine the amount of the dispersed matter in the suspension.

10. The method of claim 6 , the method further comprising measuring a flow of the suspension by comparing measurements performed at least at two different time instants with one another.