This ensures increased transfer standard repeatability, allowing for less frequent recertifications. The comparison must have a correlation coefficient of 0.9999 or greater. The derived slope and intercept is used by the client to correct or adjust the instrument's displayed ozone concentration. The comparison's slope and intercept should not be used to correct the meters reading. They should only be used to verify the instrument is operating properly.
Certifications require four consecutive comparisons against a primary flow calibrator.
It is preferred to alternate primary flow calibrators for each comparison. Each comparison must have a linear regression with a correlation coefficient of 0.9999 or greater. A certification or recertification is valid if the four most recent comparisons have a RSD less than 1 percent for the slope and a FRSD less than 1 percent for the intercept. For recertifications, the current comparison's slope must be within 1 percent of the most recent comparison's slope, otherwise, another comparison must be performed to verify the change. Additional comparisons are not required if the four most recent comparisons meet the certification requirements.