Time-Correction Model Based on Diverter Speed for a pVTt Gas Flow Primary Standard

Area of Science:

• Metrology
• Fluid Dynamics
• Instrumentation

Background:

• Volumetric primary standards (pVTt) measure gas flow rates by tracking density changes within a defined volume.
• Accurate measurement of low gas flow rates (< 12 mg/min) presents challenges, particularly concerning the diverter's impact on timing.

Purpose of the Study:

• To develop and validate a time correction model for a pVTt system to improve accuracy at low flow rates.
• To investigate the effects of diverter speed on effective collection time and implement adaptive corrections.

Main Methods:

• Implementation of a novel time correction model adapting to diverter speed in a pVTt system.
• Comparison of two time correction methods: ISO 4185 standard and dynamic pressure measurements upstream of the diverter.
• Experimental measurements of correction time at various diverter speeds for a flow rate of 9 mg/min.

Main Results:

• The developed time correction model demonstrated excellent agreement with measurements using both ISO 4185 and dynamic pressure methods.
• Measurements at 9 mg/min confirmed the model's effectiveness.
• Further tests at lower flow rates indicated that the time correction is independent of the measured flow rate.

Conclusions:

• The proposed time correction model enhances the accuracy of pVTt systems for low gas flow rate measurements.
• The model's independence from flow rate simplifies its application across a range of low flow conditions.
• Accurate timing is crucial for precise gas flow metrology.