Zero Point

• All gauges are designed to read from a minimum to a maximum value accurately. The minimum is often zero and represents no input. The zero can usually be adjusted with a front panel screw.
  
  

Span

• The span of a gauge is its full-scale point. Span corrections are made by internal adjustment of the segment tail on the gauge meter movement.
  
  

Linearity

• After the zero and span are correct, the linearity is verified. This is done by testing several points along the scale. If corrections are needed, the linkage of the gauge movement can be adjusted. Span and linearity adjustments are often interactive, so several repetitions may be needed.