Standard Equivalent Air Leak Rate Conversions for Sealed Commercial Pouch Cells
Standard air equivalent leak conversions transform empirical helium mass spectrometer readings into precise air ingress and solvent loss metrics for pouch cells.
Tracer Concentration Normalization
Meaning
Mathematical adjustments to leak detection sensor readings ensure that the values remain comparable under varying pressure and background gas levels. This mathematical procedure is known as tracer concentration normalization, and it allows for consistent leak rate evaluations across different testing chambers. The adjustment compensates for the dilution of the tracer gas in the vacuum chamber.
It provides a standardized value that is independent of the chamber size.
Calculation Base
Normalizing the sensor output requires dividing the raw reading by the concentration of the tracer gas used during calibration. If the tracer gas is diluted, tracer concentration normalization corrects the baseline to reflect the true leak size. This formula uses the ratio of helium to air to determine the corrected flow rate.
The calculation prevents false readings caused by variations in the testing gas mixture.
Quality Control
Quality teams use these adjusted values to maintain consistent standards across different factory locations. Applying tracer concentration normalization prevents the rejection of functional cells due to sensor calibration drift. It ensures that testing equipment in different assembly lines produces equivalent pass and fail decisions.
This consistency is needed to maintain high manufacturing throughput.
Testing Limit
Applying the normalized formulas requires a stable background gas measurement to avoid dividing by zero or introducing noise. When the background level of the tracer gas fluctuates, tracer concentration normalization becomes less reliable, which can lead to false positive leak detections. For this reason, testing chambers must be flushed with dry air between cycles.
This flushing step keeps the background tracer concentration low enough to allow accurate normalization, ensuring that the test results remain valid even during continuous, high-speed automated production runs.