Apparatus for automating standard voltage reference cell intercomparisons

Abstract

An apparatus is presented for performing standard cell intercomparisons. An operator selects two cells in order to compare their relative voltage values. A first terminal on each cell is coupled through a common line switch associated with that cell to a common line. A second terminal on each cell is similarly coupled through an associated A switch to an A line and through an associated B switch to a B line. A potentiometer can be used to compare the voltage on line A with the voltage on line B to determine the relative voltage difference between the cells. Various mechanisms within the apparatus insure protection of the cells. These mechanisms include: encoding of selection information to insure only one cell for the A line and only one cell for the B line is selected; limiting the power available to switches so only one switch can be turned on within a given time span; inclusion of a protection line associated with the A line, and a protection line associated with the B line so that a logic control circuit can detect when a cell is coupled to the A line or the B line and prevent a second cell from being coupled to either the A line or the B line; and, requiring an operator to simultaneously depress two pushbuttons located on a front panel of the apparatus in order to select a cell to be coupled to either the A line or the B line.