An accelerometer is a sensor that senses the dynamic motion of the surface that it is attached to by producing an electrical output which is analogous to that motion. With this, it is important to mount the accelerometer properly and ensure it is tightly coupled to the test surface to duplicate the motion from the test object to the accelerometer without discrepancies.
There are several mounting methods for accelerometers and each mounting method is suitable for different scenarios.
The stud mount method is the preferred method of mounting an accelerometer to the test object.
It yields the best results because when the accelerometer is installed in this fashion, it is “fused” together with the test surface by the clamping force of the stud. This ensures the exact duplication of motion of both bodies at all frequencies. Usually, there is a thin layer of silicone grease between mating surfaces to fill any voids between.
Studs come either as an integral part of the accelerometer or as a removable piece of the accelerometer. Removable studs are favoured as they can be easily replaced when worn out.
When the situation arises that the stud mount method is impractical or impossible, adhesive mounting is the recommended method. Such as when mounting the accelerometer on a thin sheet of metal where it is not possible to drill for stud mounting.
For adhesive mounting, some accelerometers are deigned to be mounted directly to the test surface while others require mounting adapters or bases for adhesive mounting. For the indirect method, these adapters/bases are first glued to the test surface before the accelerometers are stud mounted to them.
For the best results, the use of cyanoacrylate “instant bond” adhesives is recommended. These adhesives set quickly and only need a small amount to create a strong bond. Their adhesive property prevents “thick glue lines” between the tested surface and accelerometer that may affect readings.
Magnetic Mounting attaches accelerometers to ferromagnetic surfaces and gives the users an advantage in that the accelerometer can be moved quickly from place to place. The accelerometer is attached to the magnetic adapter (via a stud mount) before being carefully coupled to the tested surface.
In general, magnetic adapters should be used with discretion and they are rarely trusted at frequencies above 1 kHz. Response degradation in direct proportion to the weight of the accelerometer may occur and for the best results, avoid magnetic mounting to unclean surfaces, non-flat surfaces and surfaces with thick paint.
To learn more about accelerometers and how to use these instruments most effectively, contact TME Systems today!