High sensor accuracy is reliant on timely calibrations where any drift is corrected for. Common validation practice involves cross-checking the sensor with a grab sample. In this paper we simulated and evaluated the effectiveness of this common approach. The results showed that more than one grab sample was needed to detect a bias of about ten percent. The random uncertainties in the grab sample could be reduced be replicate samples, which thereby improved the bias detection. The findings indicate that careful, at the cost of less frequent validations, is recommended, as compared to the opposite and current practice.
