Choosing the right accelerometer mount: 6 effective methods explained

In a previous article, we wrote about 11 important considerations for choosing the right accelerometer. However, to achieve reliable measurement results, the mounting method is crucial for maximizing accuracy. Various mounting methods are possible, and each method affects the measurement range (frequency range) of the sensor differently. In this article, we explain the considerations you need to make when choosing the right mounting method for accelerometers.

Incorrect mounting can result in significant data errors, especially at high frequencies. For the best measurement results, it is important that the sensor is mounted as close to the machine as possible. Additionally, the surface of both the sensor and the machine should be clean, flat, smooth, scratch-free, and burr-free. If this is not the case, it can distort the signal.

Stud Mounting

The best way to mount an accelerometer is using a threaded mounting. In this method, a threaded hole is made in the machine where a stud can be screwed in. The accelerometer is then attached to the other end of the stud, also using a threaded connection. This method transfers vibrations to the accelerometer most effectively because it is entirely directly mounted on the machine, providing the highest accuracy. It is important to tighten the accelerometer with a torque wrench to ensure all sensors are securely fastened and to avoid damage from overtightening.

This mounting can be used up to about 10,000 – 20,000 Hz.

Adhesive Mounting

If drilling into the machine at the desired mounting location is not possible, or if the machine’s surface is poor, adhesive mounting can be a safe alternative. The downside of this method is that the measurement range (operational frequency range) is reduced because the adhesive dampens vibrations. Due to the damping effect, the resonant frequency is lower, thereby reducing the working range.

There are two ways to use adhesive mounting: directly bonding the sensor to the machine, or bonding a mounting stud (mounting pad) to which the sensor can be attached.

This mounting can be used up to about 7,000 – 10,000 Hz.

Temporary Measurements: Magnetic and Sensor Extensions

Magnetic mounting methods are a quick and easy option for applications where a vibration specialist periodically checks the measurements. This is often used on large machines.

Magnetic connections yield significantly poorer results at high frequencies compared to accelerometers mounted with a stud or adhesive. The biggest drawback is the lower resonant frequency and less rigid connection, which acts as a low-pass filter causing higher frequencies to be lost. Due to the larger mass, caution is advised when analyzing measurement data above 1000 Hz, as the extra mass of the magnet can significantly influence measurements on lightweight machines.

Magnet on Flat Surface

When using a magnet, ensure that the surface is clean and free of metal particles. A clean magnet on a flat surface, with a drop of oil, can provide good results up to 10,000 Hz.

This mounting is typically used up to about 5,000 – 7,000 Hz.

Magnet on Curved Surface

A magnet on a curved surface is suitable for frequencies between 2,000 and 2,500 Hz. If the aforementioned mounting methods are not feasible, this is an acceptable option.

Extension (Probe Tip)

Lastly, there is the possibility of attaching a probe tip to the sensor. This is suitable for frequencies up to 500 Hz, but it also depends on who performs the measurement. This method should only be used if all previously mentioned mounting methods are not possible.

This mounting is typically used up to about 500 Hz.