| Abstract [eng] |
One of the goals of metrology is to strive for simple, easy-to-implement methods of calibrating a measuring instrument, as a result of which time costs, tools, and human resources are reduced. For measuring instruments of different accuracy, it is necessary to perform individual error analysis, apply different mathematical models for calculating measurement uncertainty, select the number of calibration points and calibration periodicity in order to ensure the sustainability of measurements. The project analyzes the connection sequence of 0.1-2.5% accuracy class pressure leakage meters, which are widely used in the automotive electronics industry for leak testing, transferring the pressure unit value from working standards to working measuring instruments. Traceabillity is realized using a calibration procedure. The calibration procedure of leakage meters in the range from 0 to 2000 Pa differential pressure and in the range from 0 to 700 mbar (7∙104 Pa) manometric pressure is not regulated by normative documents, so the study and optimization of their calibration methodology is valuable both in terms of scientific and direct application. ATEQ F620 and Furness Controls FCO750 leakage meters, whose operating principle is based on the piezoelectric effect, were chosen for the study. To implement their calibration scheme, the calibration equipment of pressure leakage meters is completed, which includes reference 0.05% accuracy class pressure calibrators Druck DPI705E and Additel ADT681-DP. To calibrate the leakage meters, a mathematical model was created and a study of the influence of uncertainties was carried out, evaluating the difference in pressure level, resolution, hysteresis, reference systematic error and reference uncertainty, correction estimate influence, dispersion and drift of readings. The expanded leakage meter manometric pressure uncertainty of 0.1-1.5% accuracy was found to be most affected by reference, correction estimate and resolution uncertanties, while 0.1-2.5% accuracy class differential pressure expanded uncertainty is most affected by the standard uncertainties of the correction estimate, reading spread and hysteresis under standard ambient conditions. Based on the calibration results of the FCO750 and F620 type pressure leakage meters, their calibration periodicity intervals were determined, which are respectively equal to: FCO750 in the 1% accuracy range, the initial calibration interval is 2.5 years, and the periodic interval is half a year; FCO750 within 0.1% accuracy range initial calibration interval 3 years and periodic 1.5 years; The F620 has an initial calibration interval of 2 years and a periodic calibration interval of 1 year in the 1.5-2.5% accuracy range. The optimized methodology for the calibration of 0.1-2.5% accuracy class pressure leakage meters allow to achieve the minimum uncertainties of ±10.72 Pa and ±0.60 Pa, respectively, at 95% confidence probability in the ranges 0-70 kPa and 0-2000 Pa. |
