showing the type of data generated by various operational amplifiers shown in fig3 as shown in fig4 the first operational amplifier in the pre amplifier generates data k where k d 12 d 22 d 32 thereafter the second operational amplifier generates a weighed function w and a coefficient c where w w 1 w 2 w 3 and c c 11 c 12 c 13 c 21 c 22 c 23 c 31 c 32 c 33 next the third operational amplifier generates data flt where flt c 11 d 11 c 12 d 12 c 13 d 13 c 21 d 21 c 22 d 22 c 23 d 23 c 31 d 31 c 32 d 32 c 33 d 33 finally the fourth operational amplifier receives data from the first the second the third operational amplifier and generates data fo fo 1 fo 2 fo 3 where fo 1 w 1 u00d7 flt 1 u2212 w 1 u00d7 k 1 k 1 d 12 w 1 is any number fo 2 w 2 u00d7 flt 1 u2212 w 2 u00d7 k 2 k 2 d 22 w 2 is any number and fo 3 w 3 u00d7 flt 1 u2212 w 3 u00d7 k 3 k 3 d 32 w 3 is any number finally the pre filter outputs data columns fo 1 fo 2 and fo 3 to the scaling processor to produce scaled data in summary this invention uses a scaling device having a pre filter instead of a post filter and a data storage unit as in a conventional device hence scaling quality of the device is improved.