Question

What options are available to make use of my existing inventory of uniaxial piezoelectric accelerometers when a triaxial measurement is required at a single location? Previously I have not had requirements to make triaxial measurements at a single point, but now I am seeing more and more requirements based on new testing parameters. Are there additional alternatives that have developed recently that you can recommend?

Answer

There are existing options that have been available for quite some time, such as specially designed triaxial blocks, in addition to newer offerings, for making triaxial measurements. There are versions for not only piezoelectric based accelerometers (SEPE & IEPE), but also piezorestive and variable capacitance accelerometers.

2950 Triaxial mounting block - First we will address the use of existing uniaxial accelerometers in a triaxial configuration at a single mounting point. There are various versions of triaxial mounting blocks available from Endevco; however we will highlight a single version for this article. Model 2950 triaxial block is an anodized aluminum block specifically designed to allow top or side connection accelerometers to be attached with the respective coaxial cables routed in a single direction. This block can accommodate up to .75 inch. base accelerometers with a 10-32 tap. There are two mounting screws for the triax block itself (for mounting block to test article/structure) and three 10-32 cap screws for mounting the three uniaxial accelerometers to the block. These cap screws mount the accelerometers from the opposing block face so as to align the accelerometer having a side exit receptacle to be oriented as needed. Once the accelerometers are mounted correctly on the triaxial block, the block itself is mounted to the structure to be tested. See figure 1, 2950 rendering. For additional blocks having different dimensions and temperature ratings, consult our Endevco Application Engineers.

A second option that should be considered is the use of a triaxial accelerometer: A cross section of accelerometer technology types are: models 65, 2258A, 2230E, 7298. There are various models to choose from and they may provide a better footprint/mounting area option going forward. Should you not already have triaxial SEPE or IEPE accelerometers in your inventory, this may be an option to consider for new applications. See hyperlinks below.

46A - Third option is to use the pods system for triaxial configurations that the user defines as they deem appropriate. This option for triaxial measurements is the most flexible and offers a lower price point than the previous two options identified. The pods system allows for a modular and flexible triaxial arrangement based on the user's specific application requirement. The user can create their own "kits" of triaxial accelerometer configurations for specific mounting locations and ground schemes. The user can match existing uniaxial with newer 46A modules to create a customized triaxial arrangement. See figures 2 and 3, visit our website product page for more information.


Figure 1 - 2950 triaxial block


Figure 2 - 46A pods accelerometer and mounting configurations


Model 65