Adhesive bases provide an alternative mounting method and may be used when mounting by stud or screw is not practical. Using separate adhesive mounting bases is recommended to prevent the adhesive from damaging the accelerometer base or clogging the mounting threads. Most adhesive mounting bases available from PCB® also provide electrical isolation eliminating potential noise pick-up and ground loop problems. The type of adhesive recommended depends on the application. Adhesives available from PCB® include Petro wax for room temperature use and Loctite® 454 quick bonding gel for higher temperature applications up to 248 °F (120 °C). Two-part epoxies offer stiffness, which maintains high-frequency response and a permanent mount. Depending on the application, adhesives such as dental cement, hot glues, instant glues, and duct putty can be viable options.
One adhesive isn’t optimal for all applications due to the variety of mounting structures. The application environment should also be considered when choosing an adhesive. Figure 4 shows an example of an accelerometer mounted to a test structure with an adhesive mounting base.
Figure 4: Adhesively mounted accelerometer
To avoid damaging a sensor during the removal process, a debonding agent must be applied to the adhesive. There is no universal debonding agent available due to the variety of adhesives (super glues, dental cement, epoxies, etc.). The debonder for Loctite® 454 adhesive that PCB® recommends is acetone. Allow the debonding agent time (a few minutes) to penetrate the surface to properly react with the adhesive. Wait a few minutes before attempting to remove the sensor. If an adhesive other than Loctite® 454 is used, check with the sensor manufacturer for debonding recommendations.
After the debonding agent has set, an ordinary open-end wrench can be used for removal (for accelerometers with a hex base or square base). The supplied removal tool should be used for teardrop accelerometers (Figure 5). After attaching the wrench or tool, use a gentle shear (or twisting) motion (by hand only) to remove the sensor from the test structure.
Figure 5: Teardrop accelerometer model 352C22 and supplied removal tool model 039A27