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2. Measurement Process Characterization
2.3. Calibration
2.3.4. Catalog of calibration designs

Designs for electrical quantities

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 A calibration design for comparing standard cells can be constructed to be left-right balanced so that:
  • A constant bias, P, does not contaminate the estimates for the individual cells.
  • P is estimated as the average of difference measurements.
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 Left-right balanced 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.

  1. Design for 3 standard cells
  2. Design for 4 standard cells
  3. Design for 5 standard cells
  4. Design for 6 standard cells
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.
  1. Design for 4 test cells and 4 reference cells
  2. Design for 8 test cells and 8 reference cells
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.
  1. Design for 4 reference zeners and 2 test zeners
  2. Design for 4 reference zeners and 3 test zeners
Standard resistors Designs for comparing standard resistors that are used for maintaining and disseminating the ohm are listed in this section.
  1. Design for 3 reference resistors and 1 test resistor
  2. Design for 4 reference resistors and 1 test resistor
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