How Pressure Affects Gas Transmission Rate Testing (And Why AMETEK MOCON Instruments Include Barometric Pressure Sensors)
- wiphaweetnvbow
- May 13
- 2 min read
Transmission rate testing evaluates how much gas passes through a material by measuring gas absorption, diffusion, and desorption. According to Fick’s Law, the amount of gas transmitted through a material is directly proportional to the pressure (or concentration) of the test gas.
In simple terms, higher pressure means more gas molecules are pushing through the material—resulting in a higher Transmission Rate (TR). Lowering the test gas pressure reduces the number of molecules involved, leading to a lower TR. This concept is clearly shown in AMETEK MOCON's COULOX® Linearity white paper, which highlights the sensitivity and linearity of our COULOX® oxygen sensor as it measures oxygen flux through a film under gradually decreasing oxygen concentrations.
Equal-Pressure (Isostatic) Testing
AMETEK MOCON instruments use an isostatic method, where both sides of the film—test gas side and carrier gas side—are maintained at equal (ambient) pressure. However, ambient pressure varies with altitude and weather. For example, Denver (high altitude) and Honolulu (low altitude) have different barometric pressures.
To ensure consistent and accurate results across different labs and locations, all AMETEK MOCON instruments are equipped with barometric pressure sensors. These sensors automatically normalize the test results to a standard pressure of 1 atmosphere (1 atm), compensating for any ambient pressure differences.
Why It Matters
