Determination of thickness of concrete’s protective layer and arrangement of fittingsis made by devices with initial calibration characteristic that causes high error of results of measurements at field inspections of buildings because of complexity of sampling. Determination of these parameters is made with preliminary processing of samples and calibration concerning a fittings class in laboratory conditions. The difference in measurements by one device on different sites appears in result. Definition of a protective layer of concrete by a pulse induction method with the initial calibration characteristic and the calibrated values on fittings classes for determination of size of an error of field tests is carried out. The experimental data showing prospects of calibration of values concerning brand of fittings on construction sites are given.