Why is a correlation needed with my Dencytee Arc TCD probe?

An off-line correlation is a training program to relate the in-line OD signal to off-line cell density measurements for a specific cell line and process-scale. First, a correlation is calculated between the dimensionless value of the in-line signal and an off-line measurement in the desired unit (e.g., g/L or cells/mL) at each offline measuring point. Second, the software uses different ratios of the in-line transmitted and reflected light to ensure a linear correlation exists.