Sensor Mounting Options Explained

A recent Reliability + Maintenance Center article presented eight questions to answer before selecting accelerometers for particular applications. Here, Meredith Christman of IMI Sensors, Depew, NY (pcb.com), expands on the July discussion by describing the main methods for attaching those vibration sensors to equipment.

STUD MOUNT

• Maximum Frequency Response: Stud mounting an accelerometer directly to a piece of equipment provides the best possible connection and, therefore, the highest-possible frequency response from the sensor.

• Equipment Modifications/Permanency of Installation: To stud-mount a sensor to equipment, it is necessary to spot face a smooth, flat surface and then tap a perpendicular pilot hole to fit the sensor’s mounting thread. If the sensor is removed, there will be lingering evidence of the installation.

• Installation on Curved Surfaces: Stud mounting a sensor on a curved surface is not possible unless a spot-face tool is used to prepare a flat surface.

ADHESIVE MOUNT

• Maximum Frequency Response: Mounting an accelerometer with adhesive directly to the equipment provides the second best mounting methodology. Frequency response is reduced only slightly (approx. 10% to 15%), compared with a stud-mounted device.

• Equipment Modifications/Permanency of Installation: An adhesive-mounted accelerometer can easily be removed with the appropriate solvent. Once removed, there is no evidence of the past sensor mounting.

• Installation on Curved Surfaces: Adhesive mounting a sensor on a curved surface is not possible.

PAD MOUNT

• Maximum Frequency Response:  Mounting pads can be adhesively bonded or welded to an equipment surface. The sensor can then be stud-mounted to the mounting pad by drilling a tapped hole in the pad. This type of sensor mounting is considered a midway point between the stiff methodology of stud mounting and the flexible methodology of magnet mounting. Frequency response will be reduced by approximately 35%, compared with stud mounting.

• Equipment Modifications/Permanency of Installation: While a weld-mounted pad is a relatively permanent installation, an adhesive-mounted mounting pad can be easily removed with the use of an appropriate solvent.

• Installation on Curved Surfaces: Mounting a sensor on a curved surface with a mounting pad is not possible.

MAGNETIC MOUNT

• Maximum Frequency Response: Mounting an accelerometer with a magnet is a very flexible mounting methodology that will degrade the sensor’s high-frequency response by as much as 85%.

• Equipment Modifications/Permanency of Installation: The lack of required equipment modifications and the temporary nature of the installation are reasons for using magnet mounting. This approach offers the most-
convenient method of temporary sensor installation for route-based measurements and data collection.

• Installation on Curved Surfaces: Magnet mounting a sensor on a curved surface is possible when a dual-rail magnet is used.

To read the July 2018 article, “Choose the Correct Accelerometer,” click here. EP

Meredith Christman is a product-marketing manager with IMI Sensors, DePew, NY, a division of PCB Piezotronics. Learn more about a range of condition-monitoring solutions at pcb.com.