摘要 |
Detector receives optical radiation transmitted through measured object and is responsive to one or more predetermined optical absorption bands of water and cellulose and two or more separate optical bands related to spectral disturbance caused by coloring substance. The measuring unit measures, on basis of responses of the detector, a water dependent value on basis of attenuation of optical radiation in predetermined optical absorption band of water, a cellulose dependent value on basis of attenuation of optical radiation in predetermined optical absorption band of cellulose, determines general dependence of attenuation with respect to wavelength including spectral disturbance caused by coloring substance by measuring attenuations in predetermined separate optical bands apart from predetermined bands of water and cellulose, and forms a moisture value on basis of moisture dependent value, cellulose dependent value, and general dependence of attenuation for compensating for spectral disturbance of at least one coloring substance. |