Accelerometer care 1

Magnetic Mounting

Accelerometers measure shock and vibration by providing an output signal proportional to the object to which they are attached. The stiffer the mounting, the higher the natural frequency of the mounted accelerometer, will be. 

Magnetic mounting of accelerometers provides the least stiffness, while screw or stud mounting provides the greatest stiffness. 

It is not always practical to drill holes into the structure or the design of the accelerometer does not allow for screw/stud mounting, so adhesive solutions are the only way forward. 

Magnetic mounting bases offer a convenient and temporary method for attaching to magnetic surfaces. Magnets with high pull strengths provide the best high frequency response. Wedged or dual rail magnetic bases are typically used for installations on curved surfaces such as motors, compressor housings and pipes. However, dual rail magnets can significantly decrease the operational frequency range of an accelerometer. The magnetic base should be attached to a smooth, flat surface for best results. Apply a thin layer of silicone grease between the sensor and magnetic base, as well as between the magnetic base and the structure. Steel pads can be welded or epoxied in place to accept the magnetic base when surfaces are uneven or are non-magnetic. 

Caution: Magnetically mounting an accelerometer has the potential to generate very high and damaging acceleration levels. To prevent such damage, do not allow the magnet to snap on to the test structure. Gently rock or slide the assembly in place. A best practice is to attach the magnetic base to your test structure first, and then screw the accelerometer onto the magnetic base.

Do not leave a charge type accelerometer permanently connected to a magnet as this can effect the sensitivity of the accelerometer.

For more information, please contact Phil Clark. phil@cmrcalibrate.co.uk