Gas Transmission Rate Tester – Differential Pressure Method

BSG is the standard model covering O₂, CO₂, N₂ and other non-toxic gases with a wide range (0.05–100,000). PSG is the ultra-high-precision model with large/small specimen areas (38.48 / 7 cm²), a small-specimen lower limit of 0.05 and the ability to test toxic gases. Choose PSG for very small specimens or special gases.

The differential-pressure method tests O₂, CO₂, N₂ and other non-toxic gases (PSG models extend to toxic gases), and it outputs more than a single transmission figure — it also gives permeability, solubility and diffusion coefficients. That multi-parameter output is valuable whenever you need to compare how different gases behave in the same material: designing gas ratios for modified-atmosphere packaging, for instance, or determining whether a gas's barrier limitation comes from solubility or from diffusion. On the division of labour: if you care only about oxygen and need to resolve very low transmission, the isostatic coulometric method is selective for oxygen and more specialised at the low end; if you need several gases, or mechanistic parameters such as solubility and diffusion, differential pressure is the more complete choice.

They differ in test area, vacuum performance and specimen fit. BSG offers a 50 cm² circular test area, a range of 0.05–100,000 cm³/m²·24h·0.1MPa at 0.01 resolution, and a vacuum level of 1333.33 Pa. PSG offers two specimen sizes — 38.48 cm² large and 7 cm² small — with ranges of 0.01–25,000 and 0.01, resolutions of 0.01 and 0.05, a vacuum level of 133.3 Pa, and faster evacuation (below 27 Pa within 10 minutes, against 20 minutes for BSG). How to choose: BSG for routine film testing at a standard area; PSG where specimen dimensions are irregular (cut-outs from finished packs, small samples) or where stronger vacuum performance is required. PSG also extends to toxic gases — if those are involved, PSG is the only option.

Choose by range and purpose. The gravimetric cup method is closest to the pharmacopoeia and ASTM E96 classic: a wide range, finished containers can be measured directly, but each run is long — best for compliance comparison and referee testing. The electrolytic method is an absolute coulometric method suited to low-transmission films and containers. The infrared (TDLAS) method responds fast and suits trace water vapour in high-barrier materials and high-throughput work. Pick the cup method when compliance leads, electrolytic or infrared when line efficiency leads.

The differential-pressure method creates a pressure difference across the specimen and tracks the pressure rise on the low-pressure side; one instrument measures oxygen, carbon dioxide, nitrogen and other non-toxic gases, making it the general-purpose choice. The equal-pressure method keeps both sides at the same pressure and uses a coulometric sensor for oxygen only, giving higher sensitivity for the extremely low OTR of high-barrier materials. Two rules: choose differential pressure when you need several gases, coulometric when you measure oxygen only and need the lowest detection limit.

Because the transmitted amount is extremely small, you must wait until permeation reaches steady state and the accumulated signal exceeds the instrument resolution; temperature and humidity equilibration and the system background (residual oxygen or water vapour) also take time. Practical ways to shorten it: raise the test temperature and note it in the report, reduce background and leaks, use a more sensitive sensor, and add parallel test chambers. No speed-up should compromise the steady-state criterion.

The effect is significant: conditions must match the method standard and be stated in the report. Higher temperature raises transmission; for hydrophilic materials, a change in relative humidity markedly changes both water vapour and oxygen transmission. This instrument controls 15–45 °C to ±0.3 °C and covers 35%–90% RH (some models also offer 0% RH). Before comparing data between laboratories, check that both used the same temperature and humidity.

Yes. Standard models ship as-is, while chamber count, specimen size, fixtures, temperature range and software modules (including the GMP Computerized System module) can be tailored to your SOP and URS. IQ/OQ/PQ validation documentation packages are available.

Standard models usually ship in 4–8 weeks; customised builds depend on the agreed scope. Instruments are packed in export wooden cases and can move by sea, air or rail. We supply proforma invoice, packing list and certificate of origin (CO / Form E), and work under EXW, FOB, CIF or DAP terms.

We provide remote installation guidance, bilingual (Chinese/English) manuals and video training; on-site commissioning by our engineers is available. Users can self-calibrate with standard weights, reference films or calibrated leak standards, and third-party calibration certificates can be supplied.

The instrument carries a 12-month warranty from acceptance plus lifetime maintenance support. Consumables (molecular sieve, desiccant, sealing grease, printer paper) are kept in long-term stock, and key components are international brands available worldwide. We respond to technical enquiries within 24 hours.

Yes. Every instrument lists its applicable standards on the specification page (ASTM, ISO, GB, YBB, Chinese Pharmacopoeia, USP, EP, JIS, DIN, TAPPI and more). The software outputs raw records and reports suitable for audit trails, with an optional GMP / FDA 21 CFR Part 11 compliance module.

The software ships with Chinese and English interfaces; other languages can be added on request. Data export is available over RS232, USB, Ethernet or Wi-Fi, and reports can be exported to Excel, PDF or structured files for LIMS integration.