raw oscillometric pulse amplitude with the higher weight is to be corrected slightly in the next process the lower weight means the probability that the raw oscillometric pulse amplitude is affected by the motion induced artifacts is higher that is the reliability of the raw oscillometric pulse amplitude with the lower weight is lower and therefore the raw oscillometric pulse amplitude with the lower weight is to be corrected significantly in the next process according to characteristics of general blood pressure signal waveforms without motion induced artifacts at least twenty six fuzzy logic rules can be defined the following are definitions of some fuzzy logic rules taken as examples u201c if amplitude is mid and slope is a little steep als weight 1 u201d u201c if amplitude is max and slope is a little steep als weight 0 4 u201d and as shown in fig5 d the dot marks are the sequence of raw oscillometric pulse amplitudes and the star marks are the weights respectively calculated for each of the raw oscillometric pulse amplitudes the weight of each of the raw oscillometric pulse amplitudes is between 0 and 1 next the controlling processing unit 18 corrects each of raw oscillometric pulse amplitudes by use of the raw oscillometric pulse amplitudes neighboring said one raw oscillometric pulse amplitude having weights higher than a threshold to calculate the target oscillometric pulse amplitude corresponding to said one raw oscillometric pulse amplitude that is the raw oscillometric pulse amplitudes with higher reliability neighboring each of raw oscillometric pulse amplitudes are used to calculate or.