A circuit working on the bench and a finished system surviving daily use need different kinds of proof. Technology Readiness Levels, or TRLs, give teams a common way to describe that progress. The scale runs from 1, basic research, to 9, a system proven in operation.

The rating belongs to a specific technology for a specific use. You need to know what has been tested, where it was tested and what still needs proving. A prototype can work well in the workshop and still face unanswered questions on site.

These descriptions follow the UK government’s TRL definitions. We’ve linked our case studies where the work helps illustrate a stage. The links are examples, not formal TRL ratings of our clients’ products.

TRL 1-3: Research and proof of concept

TRL 1: Basic principles observed

Researchers observe a principle that might have a practical use. There is no tested application yet. At this stage, the evidence might be published research or measurements of the underlying effect.

TRL 2: A possible application takes shape

Someone identifies a use for the principle and works out what the technology would have to do. The application is still a proposal; its critical functions have not been demonstrated.

TRL 3: Proof of concept

An experiment shows that one critical function works. A small bench setup might prove a sensor can detect the right signal or that a mechanism can deliver the required movement. Nobody expects a complete product at this point.

Our published case studies start later in the process, so we don’t have a public project to link to these first three levels.

TRL 4-6: Build and test prototypes

TRL 4: Components validated in a laboratory

The team builds the key components and tests them together under controlled conditions. They can repeat the test and measure whether the critical functions meet their targets. The setup may still be a long way from the final design.

Our replacement PCB project included tracing the original schematic, designing a compatible board and testing each manufactured board before delivery. Those checks show the kind of component-level evidence a team needs, though the finished project went beyond a laboratory test.

TRL 5: Components validated in a relevant environment

The tests now reproduce conditions that matter in the intended setting. For an electronic device, that could mean electromagnetic interference. For outdoor equipment, it could mean water ingress or temperature changes. The team needs evidence that the components still work under those conditions.

For Eventum Orthopaedics, we built a pneumatic rig that operated its surgical sensor system during EMC testing. Electrical actuators inside the chamber would have interfered with the measurements, so we kept the powered controls outside and used air lines to reproduce the surgeon’s inputs.

TRL 6: A prototype demonstrated in a relevant environment

At this level, the team tests an integrated prototype rather than separate parts. It should resemble the intended system closely enough to expose problems with how the parts work together.

Our Rivelin Rail track trolley combines a friction sensor with GPS logging and a controlled water spray. We packaged the electronics for outdoor use and delivered the integrated prototype with operating documentation. The case study shows the build, though it does not document a formal TRL 6 demonstration.

TRL 7-9: Demonstrate and qualify the system

TRL 7: A system prototype demonstrated in its operational environment

The complete prototype goes into its intended setting. Operators use it with the equipment and constraints they face on a normal job. Field tests can reveal faults that never appeared in the workshop.

The Rivelin Rail trolley was built for on-track measurement. To make a TRL 7 claim, we would need documented results from representative railway use; the public case study covers the delivered prototype but does not provide those results.

TRL 8: The system is complete and qualified

The final design has passed the tests needed for its intended use, with the relevant documentation and approvals in place. Those requirements vary by application. A test rig used during medical device development will need different evidence from a rail trolley.

We delivered the Eventum test rig with endurance test records, commissioning procedures and a user guide. That documentation shows the work involved in handing over a complete, testable system. It is not a published TRL 8 assessment of Eventum’s surgical sensor.

TRL 9: Proven in operation

The finished system has a record of successful use in its intended setting. A handover or a single successful trial cannot establish that record. You need evidence from real operation.

We don’t have a public case study with that operational history, so there is no project link for TRL 9.

Choosing the next test

Before choosing a level, define the technology and where it needs to work. Then list the evidence already in hand. The gap might call for a bench test, an integrated prototype or a trial on site. That gives engineers a useful next job and gives customers something more substantial than a number.