WVP/S+ Water Vapour Permeability Tester

The WVP/S+ holds 18 moisture permeable cups simultaneously across its two-layer sample test platform — 9 cups on the upper layer and 9 cups on the lower layer, both per ASTM E96 test area requirements (28 cm² or more). All 18 specimens are exposed to identical temperature, humidity, and air velocity conditions within the same chamber, ensuring statistically valid comparisons between different fabrics or formulations in a single test run.

Seven pre-programmed conditions are available: 23°C/50% RH (ISO 8096, BS 7209); 20°C/65% RH (BS 3424); 38°C/50% RH and 38°C/90% RH (ASTM E96 variants); 40°C/50% RH and 40°C/90% RH (tropical and high-humidity conditions); and 27°C/65% RH (general textile condition). All conditions are maintained within ±0.5°C temperature and ±2% RH tolerance as specified by the relevant standards. Custom conditions outside these presets can also be entered directly.

In the wet cup method (ASTM E96 Method B / BW), the cups are filled with water and sealed with the test fabric; the vapour pressure gradient drives moisture outward through the specimen — this simulates the condition where perspiration contacts the fabric. In the dry cup method (ASTM E96 Method A), cups contain desiccant and moisture is driven inward — useful for measuring barrier properties. The WVP/S+ supports both configurations. ISO 8096, BS 7209, and BS 3424 use the wet cup approach, which is the most common method for apparel and breathable fabrics.

The WVP/S+ complies with ASTM E96/E96M (Standard Test Methods for Water Vapor Transmission of Materials), ISO 8096 (Rubber- or plastics-coated fabrics — resistance to water penetration), BS 3424 (Methods of test for coated fabrics), and BS 7209 (Specification for water vapour permeable apparel fabrics). These standards cover the major global markets for breathable textiles including the UK, EU, USA, and international export markets.

Water vapour permeability testing is essential for sportswear and performance apparel (running, cycling, outdoor), technical protective clothing (military, firefighting, hazmat suits), medical textiles and wound dressings, coated and laminated fabrics (waterproof-breathable membranes such as PTFE laminates), footwear and gloves, packaging films, and building membranes. Any product where breathability or moisture management is a key performance or safety attribute requires WVP testing for certification and buyer compliance.

Ultrasonic humidifiers generate microscopic water droplets at room temperature using high-frequency vibration, rather than heating water to produce steam. This means the humidity is added to the chamber without any accompanying heat load, eliminating the temperature interference that steam injection can introduce. The result is faster humidity response, tighter control accuracy (±1.0% RH), and more stable combined temperature-humidity conditions — which is critical when the test standard specifies tight tolerances such as ±0.5°C and ±2% RH.

The WVP/S+ requires 220VAC ±5%, 50–60Hz, single-phase power. It weighs 350 kg and measures 700×850×1800mm (L×W×H). A water supply connection is needed for the automatic water filling system, and adequate floor space and load-bearing capacity must be confirmed before installation. The optional USB/Ethernet PC interface allows test data to be saved and printed directly from the instrument. The instrument is manufactured in India by Apple Electroniks and is supplied with full installation and commissioning support.