How to ensure reliable data from wireless vibration sensors

Getting accurate data from wireless vibration sensors depends heavily on how the sensor is mounted on the monitored component. A rigid attachment is essential to guarantee a true indication of the asset’s health.

Each mounting method can influence the quality of the results. Therefore, it’s crucial to understand the different attachment techniques, their importance, and their limitations regarding vibration spectra.

Additionally, selecting the right type of vibration sensor and defining the correct installation point on the machine are equally important.

Wireless vibration sensors measure vibrations primarily along their monitoring axis. For this reason, the sensor must be installed in an optimal position with firm anchorage.

Why mounting method matters for vibration sensors

Sensors can be installed in several ways, and the frequency bandwidth of the sensor is highly sensitive to its coupling with the equipment.

The attachment method at the measurement point is one of the most critical factors for obtaining precise results. A poor attachment can introduce irrelevant resonances, severely limiting the useful frequency range of the accelerometer.

Every sensor installation has dynamic characteristics such as rigidity, added mass, and damping. If the attachment is inadequate, these factors contaminate the sensor’s frequency band. Ideally, aim for maximum rigidity to increase the resonance frequency of the installation.

There are five commonly used mounting methods, each with a maximum operational frequency.

Figure 1 shows the frequency response of these methods. Among them, the most common for machine condition monitoring are:

• Screw Attachment
• Adhesive Attachment
• Magnetic Mounting

Figure 1 – The frequency response of the methods: Screw Attachment, Adhesive Attachment, Magnetic Mounting.

Screw mounting vibration sensors

Screw mounting is typically used for sensors that remain permanently fixed. This method is considered the most efficient because it essentially integrates the sensor and the machine surface into one unit.

Sometimes, adhesive glue can be combined with the screw to prevent loosening caused by lateral or torsional vibrations. For irregular installations, metallic adhesives or resins can improve adhesion.

Although not always practical, screw mounting is the preferred method for vibration sensors because it offers the highest reliability and repeatability.

For example, the DynaLogger from the Dynamox Solution uses an M6-1 screw through its metal slot to join with the hole on the measurement surface (see Figure 2).

Figure 2 – Standard sensor installation (DynaLogger) of the Dynamox solution.

Best practices for screw mounting

• Use a spring washer or locknut to maintain tightening torque and prevent loosening. Recommended torque: 11 Nm (1.12 kgfm).
• Drill a hole at least 15 mm deep for a strong bond.
• Ensure the hole is perpendicular to the machine surface.
• For curved or irregular surfaces, use metallic adhesive or epoxy for rigidity.
• Tighten the sensor with an Allen key as specified. Do NOT use pliers or overtighten.

Avoid common mistakes and follow the good practices shown in Figure 3.

Figure 3 – Good and bad practices of screw installation.

Adhesive attachment for vibration sensors

Adhesive mounting is an alternative when drilling isn’t possible, such as on thin-walled aluminum housings or bearing surfaces.

Magnetic mounting won’t work on aluminum, making adhesive the best option in these cases.

Surface preparation is critical for adhesive mounting. A defective joint can lead to significant measurement errors. For portable setups, a support bracket can also be used.

Choose an adhesive suitable for the materials and operating environment. It must provide a rigid foundation — soft adhesives absorb high frequencies due to damping.

For Dynamox sensors, use a bicompound epoxy paste or metallic glue (approx. 2 cm³). Apply the epoxy around the outer surface of the DynaLogger, leaving a 2 mm gap from the metal slot to avoid interfering with temperature measurement.

Press the sensor firmly and orient the axes correctly. Avoid excess epoxy, as thick layers reduce rigidity and increase damping at high frequencies.

Figure 4 – Application of epoxy adhesive. Note that an excess of epoxy, with a thick layer between the sensor and machine surface, results in loss of rigidity and increased damping at high frequency and should, therefore, be used with caution.

Magnetic mounting vibration sensors

Magnetic bases are ideal for applications requiring easy removal. When mounted perpendicularly, magnetic sensors can resist forces of 20–25 kgf (196–245 N).

Magnetic pads come in various shapes, including those for curved surfaces, improving repeatability. However, displacement risk remains, affecting readings on all three axes (vertical, horizontal and axial).

Ensure the surface is truly magnetic (steel alloys with iron, nickel, cobalt) and free from irregularities or debris. Poor contact can tilt the sensor, reducing rigidity and impairing measurements.

Follow the recommendations and illustrations to maintain magnetism and achieve accurate results.

Figure 5 – Common situations that lead to the loss of adhesion of the magnetic base: mounting on surfaces with debris or non-magnetic surfaces, mounting on very hot surfaces and dropping onto other surfaces (causing loss of magnetism).

Best practices for mounting location of wireless vibration sensors

Choosing the right mounting location for a vibration sensor is just as important as selecting the attachment method. Locations that flex can distort measurements, leading to inaccurate data. For example, mounting on motor fins or guards often fails to transmit vibrations reliably from the main source.

It’s important to note that the installation location matters regardless of the attachment type. If the sensor is fixed to a flexible surface, none of the mounting methods will deliver accurate results.

Avoid flexible or lightweight structures

Vibration sensors should never be installed on light or non-rigid structures. The sensor’s weight can alter the vibrational behavior of these surfaces. As a rule of thumb, the combined weight of the sensor and its mounting accessories (screw, magnet, etc.) should be less than 10% of the weight of the vibrating structure.

Mount sensors close to rigid components

To capture accurate vibration data, always mount the sensor as close as possible to the most rigid parts of the machine — such as bearings and housings. This approach offers two key benefits:

• Lower noise levels: Reduces signal overload and prevents masking of critical vibration components.
• Direct transmission of dynamic forces: Ensures all vibration sources are detected accurately.

More specifically, position the sensor near the source of vibration of interest to avoid distorted signals from unrelated origins.

Figure 6 illustrates how mounting on flexible surfaces (guards, thin plates) versus rigid surfaces (bearings, structures) affects frequency response.

Figure 6 – Typical frequency response of flexible (guards and thin plates) or rigid (bearings and structures) locations.

The Dynamox Solution: Reliable wireless vibration monitoring

To achieve the best results with the Dynamox Solution, proper installation of DynaLoggers at the correct measurement points is essential.

By following the recommended attachment methods and selecting optimal mounting locations, you can detect all vibration sources across three axes with high precision.

Additionally, each DynaLogger includes a temperature sensor, enabling correlation between temperature changes and vibration levels.

All data is collected wirelessly and transmitted via Bluetooth to the Mobile App or Gateway, then synced to the Dynamox Platform. This integration allows for historical data analysis and informed decision-making for predictive maintenance.

Key takeaways for mounting location of wireless vibration sensors:

• Rigid attachment is essential for accurate vibration data.
• Screw mounting offers the best reliability and repeatability.
• Adhesive mounting is ideal for thin or non-drillable surfaces.
• Magnetic mounting provides flexibility but requires careful handling.
• Avoid flexible or lightweight surfaces that distort measurements.
• Combine vibration and temperature data for comprehensive asset monitoring.
• Use the Dynamox Solution for wireless, real-time, and historical analysis.

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