once again that v b is used directly the third time in the conversion process to maintain high resolution in each signal developed one other circuit is depicted in fig3 averaging circuit 330 the description of the function of this last circuit will be deferred until after a discussion of the structure and interaction of the units comprising the three separate circuits shown in fig3 according to the illustrative embodiment v b is channeled onto links 350 351 and 352 this effectively 34 splits 34 the v b input signal and makes it available to each of the three separate circuits the v b signal on link 350 is translated via a d converter 300 into a digital signal which is used to address prom 310 prom 310 is an example of a memory system suitable for storing the correction coefficient set as a set of digital signals recall that all values of v b in a given segment of the non linear thickness curve for an object are translated into a single memory address this single address is input to address register 305 coupled to a d converter 300 via link 353 address register 305 serves as a temporary holding register for the address and further functions to inhibit a new coefficient signal from being output by prom 310 for a predetermined period of.