Detection of Shifts in the Values of Saturated Standard Cells Used as References

A method of analyzing data taken in routine comparisons of a test group of saturated cells to a reference group, so that shifts in the electromotive forces of individual reference cells may be detected, is explained. Limitations on the minimum number of reference cells adequate for close tracking of cells under text become apparent from examination of data, as do the advantages of knowing precisely the electromotive force of each reference cell at the time of use. The technique is suggested as a convenient means of augmenting surveillance of the stability of individual reference cells with respect to the average of a larger group.