Mount Accelerometers Like a Pro
EP Editorial Staff | October 1, 2022
You found the perfect accelerometer. Now how do you install it?
Mounting surface, space restrictions, temperature, and portability are all important factors to consider when determining the right technique. These four time-tested options make sensor mounting simple.
This technique requires smooth, flat contact surfaces for proper operation and is recommended for permanent and secure installations and for testing at high frequencies.
Hand-tighten the mounting stud to the machine and secure the device by applying the recommended mounting torque. It’s important to use a torque wrench for installation as under-torquing the sensor may not adequately couple the device and over-
torquing may result in stud failure.
Direct adhesive mounting
When space restrictions are an issue, most sensors (except integral stud models) can be directly mounted to a machine surface. Adhesive mounting is often used for temporary installations or where the machine surface cannot be adequately prepared for stud mounting. Hot glue and wax work well for temporary mounts, whereas two-part epoxies and quick-bonding gels provide a more permanent mount.
Clean the surface thoroughly, then place a small portion of adhesive on the underside of the sensor. Firmly press down on the top of the assembly to displace any adhesive. Be careful as excessive amounts of adhesive may make sensor removal difficult. Note: Adhesive-mounted sensors often exhibit a reduction in high-frequency range. In general, smooth surfaces and stiff adhesives will provide the best frequency response.
This method involves mounting a base to the machine surface and then securing the sensor to the base. This allows easy removal of the accelerometer.
Stud mount the sensor to the appropriate adhesive mounting base. Clean the surface thoroughly to remove grease or oil, then place a small portion of adhesive on the underside of the sensor. Place a small portion of adhesive on the underside of the mounting base. Then, firmly press down on the assembly to displace any extra adhesive remaining under the base.
Magnetic mounting provides a convenient method for portable measurements and is commonly used for machinery monitoring. The correct magnet and an adequately prepared mounting surface are critical for obtaining reliable measurements, especially when high frequencies are involved. Poor installations can cause as much as a 50% drop in the sensor frequency range.
Not every magnet is suitable for all applications. Rare-earth magnets are commonly used because of their high strength. Flat magnets work well on smooth, flat surfaces, while dual-rail magnets are required for curved surfaces. In the case of non-magnetic or rough surfaces, it’s recommended to first weld, epoxy, or otherwise adhere a magnetic steel mounting pad to the test surface.
After choosing the correct magnet type, inspect the unit, checking that the mounting surfaces are flat and smooth. Stud mount the accelerometer to the magnet. Then, after cleaning the surface and checking for burrs, wipe on a light film of silicone grease, machine oil, or similar coupling fluid. Mount the magnetic sensor assembly to the prepared surface by “rocking” or “sliding” it into place. Note: Careless magnetic mounting may lead to very high and potentially damaging “g” levels. To withstand this abuse, be certain the sensor has built-in shock protection. EP
For more information about sensors and sensor mounting, visit the IMI Sensors, division of PCB Piezotronics, website at pcb.com.