IMI Industrial Vibration Sensors Katalog Seite 171

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Technical Information Accelerometers Adhesive Mounting Mounting by stud or screw may not always be practical Adhesive mounting offers an alternative mounting method The use of separate adhesive mounting bases is recommended to prevent the adhesive from damaging the accelerometer base or clogging the mounting threads Miniature accelerometers that normally contain integral mounting studs may have the stud machined off to form a flat base Most adhesive mounting bases available from PCB also provide electrical isolation This eliminates potential noise pick up and ground loop problems The type of adhesive recommended depends on the particular application Petro Wax available from PCB offers a very convenient easily removable approach for room temperature use Two part epoxies offer stiffness which maintains high frequency response and as the installation becomes a permanent mount Other adhesives such as dental cement hot glues instant glues and duct putty are also viable options with a history of success There is no one best adhesive for all applications because of the many different structural and environmental considerations such as temporary or permanent mount temperature type of surface finish and so forth To avoid damaging the accelerometers mounted with permanent adhesives a debonding agent must be applied to the adhesive prior to sensor removal With so many adhesives in use everything from super glues dental cement epoxies etc there is no universal debonding agent available The debonder for the Loctite 454 adhesive that PCB Suggests is Acetone If you are using anything other than Loctite 454 you will have to check with the individual manufactures for their debonding recommendations The debonding agent must be allowed to penetrate the surface in order to properly react with the adhesive so after the application of the agent it is advisable to wait a few minutes before removing the sensor Once the debonding agent has set you can use an ordinary open end wrench applied to the hex or square base and with a gentle shear or twisting motion by hand only the sensor can be removed from the test structure Base or square base or miniature teardrop accelerometers are supplied with a removal tool for use in the shearing motion Magnetic Mounting Magnetic mounting bases offer a very convenient temporary attachment to magnetic surfaces Magnets offering high pull strengths provide best high frequency response Wedged dual rail magnetic bases are generally used for installations on curved surfaces such as motor and compressor housings and pipes However dual rail magnets usually significantly decrease the operational frequency range of an accelerometer For best results the magnetic base should be attached to a smooth flat surface A thin layer of silicone grease should be applied between the sensor and magnetic base as well as between the magnetic base and the structure to improve surface contact continuity When surfaces are uneven or non magnetic steel pads can be welded or epoxied in place to accept the magnetic base Caution Magnetically mounting an accelerometer has the potential to generate very high and very damaging acceleration levels To prevent such damage exercise caution when attaching the magnet to your test structure and gently rock or slide the assembly in place Do not allow the magnet to snap on to the test structure as excessive shocks are generated These shocks could damage the sensor Another more ideal mounting method is to attach the magnetic base to your test structure first and then screw the accelerometer on to the magnetic base Magnet Mounted to Steel Pad Screw Mounting When installing accelerometers onto thin walled structures a cap screw passing through a hole of sufficient diameter is an acceptable means for securing the accelerometer to the structure The screw engagement length should always be checked to ensure that the screw does not bottom into the accelerometer base A thin layer of silicone grease at the mounting interface ensures high frequency transmissibility Magnet Mounted Directly to Test Structure Silicone Grease Weld or Epoxy Magnetic Base Steel Pad Magnetic Base Silicone Grease Silicone Grease 168 visit us online at www imi sensors com 1 716 684 0003