Repetibilidade e reprodutibilidade da calibração de sensor de fluxo de orifício variável com o método da seringa

Abstract

This work evaluated the repeatability and reproducibility of the calibration of a variable orifice flowmeter using the fixed volume syringe method, focusing on the possible effects of syringe stroke direction and different waveforms during calibration. We compared both sides of the flowmeter (W and B) in configurations with the side not connected to the syringe open to the room or connected to a tube. For each of the 4 possible combinations, sinusoidal flows were generated with an automated syringe. Additionally, only for the B side connected to the syringe without the tube on the W side, constant flows generated by the automated syringe, and flows generated manually by two operators (1 and 2) using a calibration syringe, were applied. Three measurements were performed for each configuration and one of them was used to generate polynomials of 5th degree for each flow direction. We considered errors of volume measurement within the range of ±3% as acceptable. For sinusoidal flows, all calibrations for the emptying syringe, and the one for the B side filling the syringe without the tube on the W side, showed repeatability. No calibration was reproducible when applied to measurements with the syringe moving in the opposite direction. For constant or manually generated flows, there was repeatability only for calibrations with the emptying syringe. When a calibration was applied to a signal from a different waveform, only the one generated by operator 1 for the emptying syringe and applied to sinusoidal flows showed acceptable errors. These results support that calibration should be performed with the syringe motion in a direction that resembles how flow is generated during application, however other factors that may affect calibration, such as other circuit assemblies and gas compositions, were not evaluated.