The world is full of mechanisms, machines and devices with moving parts. Many of these “old” pieces of equipment or technology have mechanical switches converting mechanical motions into electrical signals. Often those mechanical switches get dirty, the contacts have aged, or there are new requirements for environmental safety or switch longevity or performance. There is always a fear that it will be very difficult to replicate the exact performance of the old mechanical arrangement with a new sensing method ‐‐ “difficult” can mean too expensive, too time intensive, or that the expertise doesn’t exist to make a fail‐safe transition.  

Time and time again HSI Sensing is consulted to convert a specific mechanical motion into an electrical signal. Most of the time we are assisting, guiding, or providing the full service for our customers to convert the mechanical motion into an electrical signal. The pushback that sometimes occurs comes from the perception that reed switch technology is not as capable as the old mechanical switches. This often is true; however, we always ask “what signal are you actually switching?”  The previously employed mechanical switches are often rated 3, 5, or 10 amps switching capability. But in the new application ‐‐ now typically signaling a computerized control system ‐‐ the rating is often below 0.1 amp. Hermetically sealed switches are very capable in these signal applications.   

Mechanical switches are also activated by levers that sometimes move very small amounts. With the correct type of magnet, polarity, switch type (engineered for close differential), and shielding, the same motion can be achieved with reed switches fabricated into a proximity sensor. Now the sensor is working in a “non‐contact” method. In other words, mechanical switches need a lever to move or a button to be pushed, requiring physical contact that is also a method for wear. The reed switch‐based proximity sensor has no need of physical contact.    

Typical mechanical switches can be built with one or two sets of contacts. Reed switch‐based proximity sensors can have one, two, three, or more sets of contacts in one proximity sensor housing. If redundancy is needed for multiple independent signals, this type of assembly should be considered. Some may say reed switch technology is ancient ‐‐ it was invented in 1930s and 1940s. That is correct. But the use of reed switches in various applications is far and wide. They are cost efficient in manufacturing, simple to apply, require no power consumption to operate, and are hermetically sealed for long life.  Difficulty or simplicity is based on the knowledge of the application and how to apply the technology. HSI Sensing has many years of experience in solving conversion of mechanical motion to electrical signal. Contact us to see how we can help your conversion.

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Published On: September 10th, 2014 / Categories: Innovations, Making Sense / Tags: , , , , /

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