Correct Installation Direction of Vibration Sensors | Differences Between 3-Axis (XYZ) and Single-Axis Pencil Types

In successful vibration monitoring, the "installation direction" and "mounting method" of the sensor are the most critical factors that determine data reliability. No matter how highly accurate the sensor is, if the installation method is incorrect, you will not be able to capture the necessary anomaly signals.

This article explains the basics of how vibration propagates (in 3 axes) in rotating machinery such as motors and pumps, and the advantages of simultaneous 3-axis detection using the wireless vibration sensor "conanair".

The Meaning of the Three Directions (X, Y, Z Axes) in Vibration Measurement

Depending on the type of anomaly in rotating machinery (unbalance, misalignment, bearing defects, etc.), the direction in which the vibration appears most strongly differs. Therefore, international standards (ISO) also recommend measuring from the following three directions.

• X-Axis: Axial Direction
  Vibration in the direction parallel to the rotation axis. Large vibrations occur primarily due to misalignment (shaft deviation), rotation of a bent shaft, or thrust bearing anomalies.
• Y-Axis: Horizontal Direction (Radial)
  Vibration in the direction perpendicular to the rotation axis and horizontal to the ground. This direction is prone to strong shaking due to machine unbalance (shift in the center of gravity) or a lack of foundation rigidity.
• Z-Axis: Vertical Direction (Radial)
  Vibration in the direction perpendicular to the rotation axis and vertical (up and down relative to the ground). Like the horizontal direction, it is affected by unbalance, but because it is fixed to the foundation, the vibration tends to be smaller than in the horizontal direction. It is also highly important for detecting bearing anomalies.

To accurately capture the signs of an anomaly, it is necessary to make a comprehensive judgment based on data from all three of these axes.

The Decisive Difference Between Simultaneous 3-Axis Measurement (conanair) and Single-Axis Measurement (Pencil Type)

There is a decisive difference in operation and data quality between the "single-axis pencil-type vibration meter" easily used in the field and the "3-axis wireless vibration sensor (conanair)" permanently installed on the machine.

While the pencil type is convenient for quickly finding out "roughly how much it is shaking right now," for "trend management of minute changes"—the cornerstone of predictive maintenance—a permanently installed type like conanair, which can conduct fixed-point observation of 3 axes simultaneously under the exact same conditions, is overwhelmingly advantageous.

[Important] Sensor Mounting Methods and High-Frequency Characteristics (Field Know-How)

Just as important as the installation direction is how the sensor is fixed to the machine. Especially when measuring the "high-frequency range (acceleration)" that indicates early-stage bearing anomalies, the mounting method directly affects the sensor's sensitivity (frequency response).

The following formula is a basic model showing the relationship between the resonant frequency ( $f_n$ ) caused by the rigidity of the fixed part (spring constant $k$ ) and the mass of the sensor ( $m$ ).

In actual field environments, the following three mounting methods are mainstream. Please select one according to the target machine and the anomaly you want to detect.

• Stud (Screw) Mount [Recommended]
  A screw hole is tapped into the machine side, and the sensor is firmly fixed with a dedicated stud. It provides the highest rigidity and allows the sensor to fully demonstrate its original performance up to the high-frequency band. Essential for precision bearing diagnosis.
• Adhesive / Epoxy Mounting
  The next best option when a screw hole cannot be drilled. If the adhesive layer is thick or a soft adhesive is used, the rigidity decreases, and high-frequency components will be attenuated. The trick is to apply a hardening type of adhesive as thinly as possible.
• Magnet Mounting
  Convenient and easy to attach and detach, but the mounting rigidity is lower compared to screwing or adhesives. Because the magnet itself is prone to resonance, especially in the high-frequency range, this method is better suited for trend management of overall vibration using velocity (mid-to-low frequencies) or simplified diagnosis.

conanair is designed to flexibly accommodate these mounting methods according to the real-world situations in the field. To practice correct trend management using Raw Data, always start by "fixing it correctly" in the "correct direction."

30-Day Free Trial & Inquiry

Try Conan Air for free for 30 days. Here is what our users are saying:

• Easy installation for immediate use
• No app required; operate via web browser
• No cloud required for fully automatic measurement
• Affordable, including dedicated software

Try equipment anomaly detection and predictive maintenance for free. Please feel free to contact us.

30-Day Free Trial & Inquiry

Try Conan Air for free for 30 days. Here is what our users are saying:

• Easy installation for immediate use
• No app required; operate via web browser
• No cloud required for fully automatic measurement
• Affordable, including dedicated software

Try equipment anomaly detection and predictive maintenance for free. Please feel free to contact us.

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