Contrinex smart inductives optimise pneumatic cylinder systems

Industrial automation enables the optimisation of machine performance, with equipment designers always looking for ways to reduce cycle times without compromising safety at little or ideally no increased cost. Pneumatic systems are a typical challenge to engineers where they are commonly used to move parts between workstations using an optimal combination of cylinder size, travel speed and air consumption.

The maximum piston travel speed for a given load is generally known, but optimising the rate of acceleration and, particularly, deceleration at each end of the travel brings additional factors into play. Stopping too suddenly generates high internal forces that may overload the cylinder, while insufficient deceleration results in a sudden impact when the load reaches the limit of the allowed travel.

Cushioning, where an internal damping mechanism is designed into the cylinder, enables an optimum level of deceleration to be achieved, but requires an application-specific adjustment during commissioning. As a cylinder wears during service, its set-up becomes suboptimal, necessitating readjustment. Process engineers require a monitoring capability that identifies deviations from the specified deceleration profile; ideally, this should utilise existing sensors to avoid increased complexity and cost.


The designers identified and specified a highly versatile, cost-effective solution to the problem, namely Contrinex’s SMART Sensors. The multiple sensing modes offered in a single inductive sensor provide all the answers in a compact and robust package, ideally suited to the demanding environment.

A sensor is embedded at each end of the cylinder to provide high-resolution, real-time measurement of piston displacement and also provide a cumulative data store that allows process drift to be monitored. Designed with the needs of OEMs and system integrators in mind, Smart Sensors provide an unobtrusive fit-and-forget solution.

As the piston approaches the deceleration zone, engineers use the Smart Sensor’s inbuilt one-shot timer feature to trigger a rapid succession of displacement measurements. Taken at known time intervals and recorded in the sensor’s data store, these measurements provide a velocity gradient during the deceleration phase that, plotted over multiple process cycles, identifies deviations from the piston’s optimal deceleration profile. Consequently, readjustment is scheduled only when necessary, minimising maintenance costs.

Mounted immediately adjacent to the piston travel path, these embeddable, metal-cased M12 Smart Sensors, which have a nominal 6-mm sensing distance for carbon steel, are highly robust and resistant to vibration and mechanical shock.

Capable of measuring both lateral and axial displacement directly, these devices also offer process engineers the option to monitor temperature, vibration and process cycle count.

IO-Link connectivity, standard across the range, provides an industry-standard interface to the machine control system; the Smart Sensor’s dual-channel capability also enables a local alarm to be triggered by an event-based exception, for example, over-temperature or excessive piston travel. During initial calibration, each sensor’s configuration is stored automatically on the local IO-Link Master; this allows plug-and-play replacement of sensors should the need arise, without any loss of functionality and without any need for recalibration.

PLUS Automation is the Master Distributor for Contrinex in the UK. Find more information and read other application examples go to

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