The concentration calibration of the in‑line
refractometer PR-33 is organized in 6 layers.
The calibration of each refractometer can be
verified using standard refractive index liquids.
Field calibration determines the appropriate
adjustment to CALC. The adjusted concentration is called CONC. If there is no adjustment, CALC
and CONC are equal. Thus the chemical curve is kept intact as a firm base for the calculation,
the adjustment is merely additional terms.