Pneumatic Cylinder Sensor – An intelligent Device

Pneumatic cylinders today are compact, reliable, and cost-effective prime movers for automated equipment. There are many applications for these devices, including machinery, material handling, assembly, robotics, and medical. OEMs, integrators, and end-users face a challenge when it comes to detecting reliably whether the cylinder is fully extended, fully retracted, or somewhere in between before allowing machine movement.

To detect the position of cylinders, magnetically actuated switches or sensors are typically attache to the sides using brackets or insert into a slot in the body of the cylinder. A magnetic field sensor detects an internal magnet mounted on a moving piston through the aluminum cylinder wall.

Choosing which type of magnetic sensor to use depends on your application and data needs.

Magnetic Sensor Types

On the market, the reed switch is the most straightforward and most commonly used end-of-stroke sensor. Two ferromagnetic nickel and iron reed elements are enclose in a hermetically seal glass tube. By preventing moisture from getting to the switch elements, the tube helps minimize contact arcing. In response to an axially aligned magnet approaching the switch element, the reed elements become magnetized and are attract together, completing the circuit.

AMR and GMR sensors

Electronic sensors used by cylinder manufacturers and OEMs are either magnetoresistive technology (AMR) or giant magnetoresistive (GMR). Resistance changes are the basis for both technologies. These sensors can work with axially magnetized magnets and, in some cases, radially magnetized magnets. GMR sensors are physically smaller than AMR sensors. Their hysteresis is better, they are more sensitive, and their precision is better. You can find versions that provide reverse polarity protection, overload protection, and short circuit protection.

Initially, an AMR or GMR sensor may cost slightly more than a reed sensor, however, this cost is decreasing over time, especially if you consider the downtime when the reed switch fails. Both AMR and GMR sensors are three-wire devices, unlike the two-wire reed switches. Ultimately, AMR and GMR sensors are better solutions because they have no moving parts and typically last longer than reed switches.

square pneumatic cylinder
square pneumatic cylinder

A position detection sensor is available for both C-slots and T-slots

On the extrusion of the cylinder body, pneumatic cylinders typically have either a C-slot or T-slot feature. Most sensor housings have the same profile, and the sensor can either drop into the slot from above and tightened with a screw or slid into the cylinder from the end if there is no end plate. Additional brackets are available that can fit either a C-slot or a T-slot sensor on round cylinders or tie rod cylinders. Ultimately, this will reduce the number of sensor part numbers and inventory for end-users and OEMs and enable them to meet the needs of more applications.

Pneumatic cylinders now have more options than ever before for piston position detection, including different housing styles to match various cylinder extrusions. In addition, two sensors – one for extended and one for retracted – are available, each sharing a single, four-pin connector. For harsh welding applications, magnetic sensors are now available with weld field immunity.

Likewise, technology has advanced. Now, cylinder sensors can be taught to trigger at certain points along with the piston’s travel. The user simply moves the piston to the desired location and presses a button to set the switching location. Additionally, this teachable sensor can connect to IO-Link for up to eight switching points for flexibility in multiple applications.

Several users have abandoned reed switches due to their high failure rate in favor of mechanical or inductive sensors to detect pneumatic cylinder position over the years. GMR and AMR sensors are smaller, faster, easier to integrate, and more reliable. With advances in sensor technology, AMR and GMR sensors should now be the primary solution for detecting cylinder position.

Airmax Pneumatics Ltd is one of the best & experienced manufacturers of a square pneumatic cylinder in India. Airmax pneumatics have a wide range of pneumatic cylinders and pneumatic valves.


We are the leading Air Preparation Unit manufacturer in India. This is a combination of Filter, Regulator & Lubricator so it is also known as FRL Unit.

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