Metrology is very important for nondestructive testing. The accurate evaluation of NDT instruments and technologies metrological parameters is а problem. It should be taken into consideration that the parameters (such as accuracy, threshold of sensitivity etc.) stated in the delivery documentation can differ significantly from those when the instruments and technologies are used in practice. If this difference is not taken into account, testing results can be substantially worse than they had been expected. The NDT technicians must be qualified enough to avoid this. Requirements for personnel skills are now included in the standards and norms on NDT technologies for concrete objects. Personnel qualification requirements regarding to NDT of steel wire ropes are now under consideration. Unfortunately, technicians do not always meet the requirements. This applies to almost all NDT methods and devices but especially to electromagnetic and magnetic flow leakage methods when they are used for testing of ferromagnetic objects, such as steel wire ropes, steel-cord conveyor belts, tubes, oil and gas tanks. The paper can be useful for NDT specialists in their practice of ferromagnetic objects testing, particularly of steel wire ropes.