Study on the Implementation of Single Pressure Balance with Iterative A-B-A-B-A Method in the Differential Pressure Calibration of Ventilator Tester

Differential pressure measurement is of increasing importance for many industrial applications, for example in oil and gas industry, as well as in the medical application such as the differential pressure application in the ventilator and ventilator tester. The demands of accuracy in differential pressure measurement are increasing as well through the traceability chain into the primary standard. In this study, two differential pressure calibration methods have been successfully implemented in the ``Standar Nasional Satuan Ukuran-Badan Standardisasi Nasional (SNSU-BSN)'' as the national metrology institute of Indonesia to calibrate the differential pressure of the ventilator tester. The first method is by generating the differential pressure reference value from two pressure balances and the second one is by using a single pressure balance with the aid of air reservoir, precise digital pressure monitor, and the iterative A-B-A-B-A methods from the previous study. Both methods measurement results show good agreement by each other with the Normalized Error less than 1.0 from 0 to 100 mbar. The major uncertainty contributions in both methods came from the hysteresis of the DUT. However, the expanded uncertainty in single pressure balance method is larger than the double pressure balance method due to the instability of the pressure line that affects the variation of DUT indication. It can be concluded that either two pressure balances or single pressure balance can be used by the laboratory for differential pressure calibration, regardless by considering the available facility and the ease of performing the calibration.