Floating Magnets vs Sliding Captive Magnets on Transducers
Wednesday, October 16, 2019 4:56:10 PM America/New_York
- Floating magnets overcome the typical issue of debris and sticky fluid buildup overtime on the transducer track or rod. This is the main cause of mechanical failure on a sliding track magnet.
- They can be mounted directly on the moving part, so machine wear is compensated, giving you a more realistic position over time. It allows you to monitor machine part wear.
- They are easier to mount to the moving part versus a rod and possibly 2 ball or eye swivels- where you have 1 on the magnet and one on moving part.
- Magnetostrictive technology has advanced to allow a greater gap between the sensor inside the track and the magnet itself. Distance is dependent on transducer and magnet type.
- The technology advances have also allowed slightly more variance in magnet to transducer distance (X) over the length of the device within reason. Also, non- parallel movement (Y) is now more forgiving. Still should not allow both! The transducer should be mounted parallel to the moving part.
- There are many options available for floating magnet types.
- One issue is they cannot be mounted directly to steel or iron. Insulated mounting blocks are available with the magnets, or you can make your own non-ferrous mount.
- EMF or high inductive local interference will also affect floating magnets. In these environments do not use a floating magnet.
- Captive magnets are used in relatively clean environments.
- They are used where you cannot put the transducer body close to the moving part.
- A common perception is that the bearing surfaces and swivel eyes will wear with time. This is true only where direction change is sudden and at high speeds. Also -dirt/oil. Usually not an issue.
- As position repeatability is the most typical and desired function of any transducer even if play develops it may not be an issue if measurement is only in one direction.
- 3 more parts to break.
- The main reason for captive magnet use? X/Y variance of magnet distance to the transducer will never vary and a floating magnet will not work in the application.