Quick Tips
In this edition of Quick Tips, we will briefly discuss proper mounting considerations for accelerometers. Ideally, an accelerometer should be in direct contact with what it's trying to measure. Requirements for surface flatness, mounting torque (for screw-mounted devices) or mounting material (for adhesive-mounted devices) need to be understood and implemented to assure quality measurements.
Surface Flatness
For all devices and mounting methods, an area twice the size of the accelerometer should be prepared. In some cases, an area larger than two times the size of the accelerometer is necessary to allow for cable management. The prepared area should have a surface flatness of 0.0003" TIR and a surface roughness of 32 microinches. The surface should have perpendicularity to the vibration source of no more than 1° to help eliminate cross-axis motion sensitivity. For those devices that are screw mounted, the tapped hole must be perpendicular to the surface ±1°.
Surface Preparation
For screw-mount transducers, the transducer should be mounted to the surface with some kind of couplant. For ambient temperature tests, this can be light oil or ultrasonic couplant. For other temperatures, different substances may be required to effectively couple the vibration to the accelerometer effectively and withstand the temperature required to perform the test. For 10-32 thread integral stud or tapped hole type piezoelectric and Isotron¨ accelerometers, the recommended mounting torque is 18 in/lb. A device that will assist in mounting and removing these devices is our 2940 plastic wrench adapter. This tool is essential for accelerometers that have a top or side mount connector such as Endevco models 2271A and 7201. We also offer a variety of other sizes and shapes of wrench adapters for most of our PE and Isotron® devices.
For adhesively mounted accelerometers, please see Endevco technical paper TP312, which discusses in more detail all the possible combinations of mounting techniques. A wrench adapter is also available for dismounting the smaller of these devices, our 2943B.
In future Quick Tips we will discuss adhesively mounted device removal. This will assist many of you in preventing damage to your transducers from improper adhesive removal techniques.
May all your Measurement Endeavors be successful!
Bob Rosenberg, Endevco/Meggitt Applications Expert
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