Potential Error in Linearized FPD Responses for Sulfur

This paper demonstrates the inherent error that can be introduced when a FPD response linearizer with a fixed exponential n-factor of 2.0 is used for the analysis of sulfur-containing compounds. The magnitude of the potential resultant error with such a device is shown to be in the range of 10% to approximately 400% when n varies from 2.0 to 1.2. The experimental n-factors for H2S, CH3SCH3, CH3SSCH3, and SO2 were found to be less than the theoretical value of n = 2. Thus, the error due to a linearization circuit that assumes that the FPD response is proportional to the square of the sulfur concentration can be considerable and may severely limit the usefulness of the commercial linearizers. Specific recommendations are discussed to minimize this type of error.