What is Individual Zero?
- wiphaweetnvbow
- May 15
- 2 min read
Updated: 5 days ago
A Key Technique for Accurate Permeation Measurements
Accurately measuring gas transmission rates (TR) requires more than just advanced instrumentation—it also demands precise background correction. One crucial function built into permeation testing instruments is Individual Zero, which eliminates bias caused by system leakage or background permeation unrelated to the sample itself.
How Does Individual Zero Work?
Before or after the actual test, the instrument performs a baseline measurement under the same conditions in which the sample is mounted. This value—called the Individual Zero—is subtracted from the measured transmission rate to obtain the true permeation rate of the sample.
Calculation Formula:
Measured TR – Individual Zero = True TR of the Sample
How Individual Zero Is Applied in Different Tests:
OTR (Oxygen Transmission Rate): Nitrogen/Hydrogen carrier gas flows on both the test gas and carrier gas sides of the film. The COULOX® sensor measures background system bias in the actual mounting setup.
WVTR (Water Vapor Transmission Rate): Dry nitrogen is used on both sides of the film for a precise RH testing, or a foil is placed instead of a sample when testing at 100% RH, to assess system bias.
Whole Package Testing: A sealed loop of 1/8” copper tubing is used to simulate a perfect, leak-free package and measure system leakage.
Where Can Background Permeation Originate?
Internal plumbing and seals in the instrument
The interface between the sample and the carrier gas side of the diffusion cell
Leakage at the sample’s edges
