Question

I have an accelerometer that is intended to be adhesively mounted. What type of adhesive do you recommend I use?

Answer

The exact choice of adhesive, of course, will be highly dependent on your particular circumstances. However, in a typical test situation, Endevco generally recommends the use of a cyanoacrylate adhesive, also known as "super glue." Cyanoacrylate is a one-part (no mixing required) chemical adhesive that is widely available in bottles. Cyanoacrylate is capable of curing to a very thin bond line, and, most importantly, the cured material in the bond is very stiff. This property is key to achieving a successful accelerometer mounting. Stiffness in the mounting, whether it be adhesive or mechanical, ensures that high frequency vibrations are not attenuated before they reach the accelerometer.

The trade-off, however, is reduced strength of the bond, at least in the shear direction (parallel to the bond line, perpendicular to the sensitive axis of the accelerometer). Cyanoacrylates also have a relatively narrow temperature range. At the extremes of the adhesive's temperature specification, the bond can weaken, attenuating the high-frequency vibrations to the accelerometer. But for a typical test scenario, these are often not serious problems, as the test is often brief and well temperature controlled.

Epoxy adhesive is an alternative when these problems become more serious. Epoxies have tremendous strength and wide temperature specifications. To achieve this strength, however, cured epoxy bonds are more flexible than one made with a cyanoacrylate. This flexibility can give rise to attenuation of high frequency vibrations before they reach the accelerometer as well. This trade-off may be acceptable if your application requires more strength and temperature range than a cyanoacrylate can give.

Please see Endevco technical paper TP312 on our website for more details.

One final note: When removing an adhesively mounted accelerometer, the temptation to strike the accelerometer to break the adhesive bond is often great. This is particularly true when using a cyanoacrylate. Endevco does not recommend or endorse this practice. The amount of force used to remove an accelerometer this way is often well above the specified shock limit of the sensor and can severely damage it. At the very least, the performance of the accelerometer could be degraded, particularly if the action is repeated over time. Endevco recommends the use of a solvent to soften up the bond first. Once the bond is softened up, removal of the accelerometer should not require a great amount of force, thus preventing damage to the sensor.