Measurement Process Characterization
2.3.4. Catalog of calibration designs
|Standard cells||Banks of saturated standard cells that are nominally one volt are the basis for maintaining the unit of voltage in many laboratories.|
|Bias problem||It has been observed that potentiometer measurements of the difference between two saturated standard cells, connected in series opposition, are effected by a thermal emf which remains constant even when the direction of the circuit is reversed.|
|Designs for eliminating bias I>||
A calibration design for comparing standard cells can be
constructed to be left-right balanced so that:
|Designs for electrical quantities||Designs are given for the following classes of electrical artifacts. These designs are left-right balanced and may be appropriate for artifacts other than electrical standards.|
|Standard cells in a single box||
designs for comparing standard cells among themselves where the
restraint is over all reference cells are listed below. These designs
are not appropriate for assigning values to test cells.
Estimates for individual standard cells and the bias term, P, are shown under the heading, 'SOLUTION MATRIX'. These designs also have the advantage of requiring a change of connections to only one cell at a time.
|Test cells||Calibration designs for assigning values to test cells in a common environment on the basis of comparisons with reference cells with known values are shown below. The designs in this catalog are left-right balanced.|
|Zeners||Increasingly, zeners are replacing saturated standard cells as artifacts for maintaining and disseminating the volt. Values are assigned to test zeners, based on a group of reference zeners, using calibration designs.|
|Standard resistors||Designs for comparing standard resistors that are used for maintaining and disseminating the ohm are listed in this section.|