Inside Work Package Four: Sensor Prototypes Under Environmental Stress

The DOCA Project is developing an online optical sensor capable of spotting oil contamination in high-purity compressed air, whether it appears as liquid droplets, fine aerosols, or invisible vapour. Work Package 4 sits at the heart of that ambition, transforming the optical and electronic concepts refined in earlier work packages into a tangible device that can be built, stressed, and measured under controlled conditions.

Compressed air rarely behaves the same way twice. A sensor that performs flawlessly on a calm laboratory bench may drift when temperature swings, humidity climbs, or vibration rattles its housing. Work Package 4 was therefore designed to confront those variables head-on, fabricating the first physical prototypes and then exposing them to the kind of punishing conditions found in real production halls, hospital basements, and pharmaceutical cleanrooms.

The goal is simple but demanding: deliver a detector whose readings remain trustworthy when the environment around it is anything but stable. For partners and end users in Australia, where ambient conditions shift sharply between Darwin's tropical humidity and Hobart's cooler coastal air, that robustness is more than a technical preference. It is a baseline requirement for any contamination monitoring tool to be useful in local industry.

Building the first optical sensor prototype

The fabrication phase began with translating the optical design into hardware. Engineers selected light sources, photodetectors, and beam-shaping optics chosen for their stability across wide temperature ranges, then integrated them onto a compact optical bench that could fit inside a process-line housing. Special care was taken with the optical path, since even a fraction of a millimetre of misalignment can compromise the sensor's ability to distinguish oil vapour from background noise.

Mechanical design followed. The housing had to withstand pressure fluctuations typical of industrial compressed air lines, while remaining easy to mount on existing pipework. Materials were chosen to resist corrosion from any oil residues the sensor was designed to detect, ensuring the device would not contaminate its own measurement environment over time.

Assembly and quality control on the bench

Once individual components arrived, the team assembled them under clean conditions, calibrating each unit against reference oil concentrations. A documented assembly procedure was followed so that every prototype behaved consistently, allowing meaningful comparisons later in the environmental test campaign. Each unit was then logged, photographed, and serialised for traceability.

Initial bench testing confirmed that the optical core could reliably resolve low parts-per-million oil levels in compressed air. This gave the consortium confidence to move from controlled laboratory conditions into the far harsher environment of the climate chamber.

Environmental chamber testing protocols

The climate chamber is where Work Package 4 becomes unforgiving. Prototypes were subjected to temperature sweeps ranging from well below freezing to elevated process-line heat, alongside relative humidity cycles designed to mimic tropical and temperate operating sites. Vibration tests simulated the mechanical stress imposed by nearby compressors, while pressure-cycling routines replicated the on-off rhythms of typical industrial air systems.

Australian standards such as AS/NZS ISO 8573, which define compressed air purity classes for use in pharmaceutical manufacturing and food processing, shaped the acceptance criteria for these trials. Compliance with these benchmarks ensures the sensor's readings can support the kind of audit trails required by Australian manufacturers supplying regulated markets.

Results across temperature and humidity sweeps

Across the temperature and humidity envelopes, the prototypes held their calibration within tight margins. The optical signal remained stable enough to resolve oil contamination at the lowest target thresholds, even when ambient humidity fluctuated by several tens of percent. Vibration testing produced only minor shifts, which were compensated through the sensor's onboard signal processing.

The most revealing data came from combined stress tests, where temperature, humidity, and mechanical load were varied simultaneously. These mirrored conditions found in places like a Brisbane automotive plant during a humid summer, or a Melbourne hospital pharmacy running round-the-clock ventilation. The prototypes passed, confirming the design's resilience in scenarios that matter to local operators.

Industrial relevance across Australian sectors

For Australian pharmaceutical manufacturers supplying the Therapeutic Goods Administration-regulated market, a sensor that survives a wide climate envelope without recalibration reduces both compliance cost and downtime. The same holds for cleanroom operators in Sydney's medical device cluster, semiconductor facilities in Perth, and food processors across regional Queensland who rely on Class 1 or Class 2 air to keep products safe.

By validating the prototype under conditions that mimic these demanding environments, Work Package 4 moves the DOCA Project closer to a commercial sensor that Australian industries can deploy with confidence. Detailed test reports, datasets, and design documentation are being published on this site as work progresses.

If your team works with high-purity compressed air and would like to follow the prototype's journey into industrial validation, subscribe to the DOCA Project updates or get in touch through the contact page to explore collaboration opportunities.