Developing an IO-Link Fluid Level Sensor
Sometimes a project isn't about reinventing the sensing technology itself. Instead, the challenge is finding a completely new way for that technology to communicate with the wider system.
EMP Designs has previously developed sensing modules for HR Wallingford that measure changes in water level, including the height of waves. The underlying sensing principle was already well established, and previous versions of the module had used EtherCAT to communicate with the wider industrial control system.
For this latest project, however, HR Wallingford asked us to develop a new version capable of communicating using IO-Link.
For EMP, that meant working with a communications system we hadn't previously implemented.
Measuring Rapid Changes in Water Level
The module is designed to work with HR Wallingford's existing probes, which determine water level by measuring changes in electrical resistance.
As the level of water around the probe changes, its electrical characteristics change accordingly. The electronics then process this information to provide a measurement of the fluid level.
Because the system can respond quickly to changes, it can be used in applications where the level is continually moving, such as monitoring waves as well as more conventional fluid-level measurement.
The sensing side of the project was familiar territory for us.
The new challenge was getting that information onto an IO-Link network.
Learning a New Industrial Protocol
Our previous modules communicated using EtherCAT, so moving to IO-Link required a different approach.
The first stage of the project involved considerable research into how the protocol operates and how an IO-Link device communicates with an IO-Link master.
We investigated purchasing an existing software library to handle the communication, but the available option was relatively expensive. Instead, we decided to develop the required software ourselves.
That turned what initially appeared to be a communications-interface change into a much more substantial firmware-development project.
Developing Our Own IO-Link Software
A large part of the development involved working through the relevant technical documentation and building the communications software required for our device.
The IO-Link connection provides power to the sensor while a switched communication line is used to exchange information between the device and the IO-Link master.
Developing the software meant repeatedly comparing the behaviour of our implementation against the technical documentation, analysing the electrical signals and examining the data being transmitted in both directions.
Each stage required us to establish that the correct data was being packaged, transmitted and interpreted as expected.
It was very much a process of developing, testing, analysing and refining the communication until the device behaved correctly on the network.
More Than Simply Sending a Measurement
One of the particularly interesting aspects of IO-Link is that the device does more than simply transmit a fluid-level value.
When the finished module is connected to an IO-Link master, the master can scan the network and identify the device.
Information associated with that particular sensor can then be retrieved so that the system knows what has been connected.
For our development team, seeing a completely new piece of hardware being detected and communicating correctly after developing the protocol implementation ourselves was a particularly satisfying milestone.
A Compact New Sensor Module
The result is a very small sensor module capable of taking the established fluid-level measurement and making that data available through an IO-Link network.
Although the finished electronics are compact, a considerable amount of development sits behind them.
The project combined:
Fluid-level sensing electronics
Signal processing
IO-Link communications
Embedded firmware development
Industrial network integration
Protocol analysis and debugging
Device identification and configuration
At the time of writing, the new module has reached the customer testing stage.
Extending Proven Technology
This project is a good example of the work we regularly undertake at EMP Designs.
The original sensing technology was already proven. The challenge was taking that technology and adapting it to work within a different industrial control environment.
Rather than being limited to the communications systems we had used before, we researched a new protocol, developed the necessary firmware and produced a compact piece of hardware capable of integrating the existing measurement technology into an IO-Link system.
Sometimes bespoke electronic design isn't about starting again.
It's about taking something that already works and giving it an entirely new way to communicate.
