Abstract: An apparatus for measuring flowable substance which has at least three microwave sensor elements arranged at separate locations in a measurement chamber in contact with the flowable substance. The sensor elements operate as at least two transmitter-receiver pairs, which transmit and receive microwave radiation via at last two paths of different lengths, through layers of dirt on the sensor elements and the flowable substance for eliminating an effect of dirt layers on the sensor elements from the measurement result. A signal processing unit has a controller which is configured to control feed of at least one substance which has an effect on the measured value of the flowable substance to the chamber on the basis of the measured value of the desired property of the flowable substance.

Abstract: An apparatus for measuring flowable substance which has at least three microwave sensor elements arranged at separate locations in a measurement chamber in contact with the flowable substance. The sensor elements operate as at least two transmitter-receiver pairs, which transmit and receive microwave radiation via at last two paths of different lengths, through layers of dirt on the sensor elements and the flowable substance for eliminating an effect of dirt layers on the sensor elements from the measurement result. A signal processing unit has a controller which is configured to control feed of at least one substance which has an effect on the measured value of the flowable substance to the chamber on the basis of the measured value of the desired property of the flowable substance.

Abstract: A sensor measures a sample in a measuring cell including a helix conductor. The shell structure of the measuring cell is made of an electrically non-conductive material. The measuring cell and at least part of the helix conductor are placeable inside a chamber. A radio-frequency signal input element couples a radio-frequency signal to the chamber to form a helix resonance. A radio-frequency signal output element is responsive to a helix resonance of the helix conductor and transmits a radio-frequency signal for measurement. A device for measuring a sample in a measuring cell includes the sensor, a radio-frequency signal source, and a measuring and control part. The radio-frequency signal source produces a radio-frequency signal to the input element. The measuring and control part measures a property of a sample on the basis of a resonance frequency.

Abstract: An electromagnetic field tuning and detection apparatus generates in to a material space and in at least two different directions radio frequency electromagnetic fields adapted to resonate in different directions at a different frequency on the basis of a material insertable into the material space; and a signal processing unit configured to determine a moisture content of the material on the basis of a resonance frequency of each electromagnetic field and quality of each resonance in different directions. While controlling a process, a control system comprises a measurement chamber and an electromagnetic field tuning and detection apparatus placed on each material feed line of the process. A controller may control the process on the basis of each determined moisture content on each feed line.

Abstract: An electromagnetic field tuning and detection apparatus generates in to a material space and in at least two different directions radio frequency electromagnetic fields adapted to resonate in different directions at a different frequency on the basis of a material insertable into the material space; and a signal processing unit configured to determine a moisture content of the material on the basis of a resonance frequency of each electromagnetic field and quality of each resonance in different directions. While controlling a process, a control system comprises a measurement chamber and an electromagnetic field tuning and detection apparatus placed on each material feed line of the process. A controller may control the process on the basis of each determined moisture content on each feed line.

Abstract: For measuring the water content of a web in the wire section of a paper machine, at least one radiofrequency-operated resonator sensor forms an electric near field, in which a web affects the resonance frequency of each resonator sensor. The water content of the web is measured as a function of the resonance frequency of each resonator sensor in a measuring unit.

Abstract: A generator generates radio-frequency electromagnetic radiation to a resonator whose resonance frequency is affected by a characteristic to be measured of an object to be measured. A receiver receives radio-frequency electromagnetic radiation from the resonator and a signal processing unit searches for a resonance frequency of the resonator for measuring the characteristic to be measured. The generator comprises a digital frequency synthesizer for scanning a frequency of radio-frequency electromagnetic radiation to be applied to the resonator over a desired frequency band by using discrete measuring frequencies.

Abstract: A generator generates radio-frequency electromagnetic radiation to a resonator whose resonance frequency is affected by a characteristic to be measured of an object to be measured. A receiver receives radio-frequency electromagnetic radiation from the resonator and a signal processing unit searches for a resonance frequency of the resonator for measuring the characteristic to be measured. The generator comprises a digital frequency synthesizer for scanning a frequency of radio-frequency electromagnetic radiation to be applied to the resonator over a desired frequency band by using discrete measuring frequencies.

Abstract: An object to be measured is measured using microwave radiation. Oscillation energy is generated by means of a feedback coupled active unit. The solution involves generating resonance into at least one oscillator, each oscillator comprising at least one open resonator, each resonator being coupled to at least one active unit, by using the object to be measured as a functional part of the resonator, the object to be measured causing a resonance frequency dependent on the location of a surface of the object to be measured to be generated in each oscillator. A measurement part determines at least one characteristic of the object to be measured on the basis of the resonance frequency of each oscillator.