What does “monitoring by metrological redundancy” mean?

This is the possibility of having two “references” in the same place in order to determine the coherency of the measurement results between two items of equipment. If the results are incoherent, it is necessary to refer to an external laboratory in order to solve the ambiguity. Readers can refer to "Surveillance des processus de mesure" (Monitoring of measurement processes) published by the CFM.