The Pros and Cons of End-of-Stroke Detection with Reed Switches

Pneumatic cylinders are used in many applications as prime movers in machinery, material handling, assembly, robotics, medical, and the list could go on. One of the challenges facing OEM’s integrators and end users is to detect reliably whether the cylinder has been fully extended or retracted before allowing machine movement. Solutions include the use of inductive sensors with some sort of target and internally mounted magnet (by the cylinder manufacturer) on the cylinder piston. In my previous blog, I discussed the two primary magnets, axially and radially magnetized magnets, used by cylinder manufacturers. Now, we will review one of the most commonly used magnetic field sensors to detect extension and retraction of the cylinder…the well-known reed switch.

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Flush or Non-Flush, Looks Can Be Deceiving

Written by: Jeff Himes

In almost all inductive proximity sensor applications the housing design and mounting method of the sensor need to be taken into consideration.  Sensor housing designs have historically been described as shielded (sometimes called flush) or non-shielded (sometimes called non-flush).  In reality the terms shielded and flush have different meanings just as non-shielded and non-flush have different meanings.  By using these terms interchangeably some confusion is typically created.  Additionally, a new term of “quasi-flush” has entered the market.  Let’s take a closer look at these terms and what they really mean. Continue reading “Flush or Non-Flush, Looks Can Be Deceiving”

Magnetic Field Sensors – Are Magnets Different?

It’s 3:00 AM and your machine has come to a screeching halt because, according to your PLC, the cylinder that holds a part in place is neither extended nor retracted.  After looking at the cylinder, you see it is extended just as it should be however; the cylinder-mounted sensor is not detecting the magnet.  No problem, you have another magnetic field sensor that will fit but it does not work either, so what is the problem? Another bad sensor? Maybe not, it could be the sensor and the magnet is incompatible.

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