Designs for surveillance of the volt maintained by a small group of saturated standard cells

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be listed or referred to in the open literature. FOREWORD When a local standard such as that for electromotive force is maintained by a group of standards, procedures must be established to provide evidence that the group has maintained its original value. One also needs methods for the transfer of the value to test items that provide efficient use of measurement effort while monitoring the measurement process and providing information for updating the values of process parameters. Solutions to the more general problem of transferring the value from laboratory to laboratory and of maintaining agreement among laboratories depend on the existence of control within the laboratories. This note is one of a number of contemplated reports having the general aim of providing methods for the surveillance of measurement processes with emphasis on the amount and kind of information needed for the estimation and control of the uncertainty in measurement. This technical note describes a procedure for maintaining surveillance over a small group of saturated standard cells. The measurement process is briefly discussed and the principle of left-right balance as a means of eliminating certain systematic errors is developed. Specific designs and their analysis for intercomparing 3, 4, 5 and 6 cells in a single temperature controlled environment are given. Procedures for setting up control charts on the appropriate parameters are given, and a technique is described for detecting certain types of systematic errors.