Understanding Triboelectric Noise
Portable balancer & Vibration analyzer Balanset-1A
Balanset-1A is a portable, USB-powered vibration analyzer and balancer for one- and two-plane balancing of rotors in their own bearings. The Full Kit includes the interface unit, two vibration sensors, optical laser tachometer, reflective tape, Windows balancing software on a USB drive, magnetic stand, digital scale and transport case. Requires a compatible Windows computer with a free USB port; computer …
Vibration sensor
Vibration sensor for Balanset balancing devices, based on the ADXL335 accelerometer. Supplied with a 5 m cable as standard for measuring vibration during rotor balancing and analysis. A 10 m cable option is available.
Optical Sensor (Laser Tachometer)
Optical laser sensor for Balanset balancing devices, based on the modified HS2234 tachometer. Measures rotational speed without contact using a reflective mark on the rotor. Supplied with a 5 m cable as standard; a 10 m cable option is available.
Balanset-4
Balanset-4 is a four-channel vibration analyzer and balancing system for correction in one to four planes. Designed for cardan shafts and rotors supported on four bearings, it can also serve as the measuring system for a balancing machine. The kit includes four vibration sensors, an optical laser tachometer, USB interface, software, magnetic stand, scale and transport case.
Magnetic Stand Insize-60-kgf
Adjustable magnetic stand for positioning the laser RPM sensor in Balanset balancing kits. The switchable magnetic base provides up to 60 kgf of holding force on suitable ferromagnetic surfaces. Adjustable arms and joints help align the sensor with the reflective mark on the rotor.
Reflective tape
Silver self-adhesive reflective tape for the optical laser tachometer in Balanset balancing kits. Apply a small piece to the rotor to provide a reflective reference mark for rotational speed measurement. Supplied as a 1 m length for multiple setups.
Dynamic balancer “Balanset-1A” OEM
Balanset-1A OEM is the core measuring kit for one- and two-plane rotor balancing and vibration analysis. It includes the USB interface unit, two vibration sensors, optical laser tachometer, reflective tape and Windows balancing software on a USB drive. Compared with the Full Kit, the magnetic stand, digital scale and transport case are not included. Requires a compatible Windows computer with …
Triboelectric noise is a form of electrical interference that contaminates vibration signals, particularly those from piezoelectric accelerometers. It is a low-frequency, non-repeatable noise generated inside the sensor cable itself when the cable is subjected to mechanical motion — bending, flexing, or being struck. Because the noise has nothing to do with the actual vibration of the machine, it can produce serious measurement errors if it is not understood and controlled.
1. Definition: What is Triboelectric Noise?
Triboelectric noise is best thought of as a self-generated artefact: the cable carrying the signal is also, when it moves, creating a spurious signal of its own. It is most troublesome with piezoelectric accelerometers because their output is a tiny electrical charge fed into a very high-impedance amplifier, and that amplifier cannot tell a genuine charge from the machine apart from a stray charge created in the cable. The contamination is real, but the machine it appears to describe is not vibrating that way at all.
2. The Cause: The Triboelectric Effect
The noise is generated by the triboelectric effect — the same physics that builds up static when you rub two dissimilar materials together and then separate them. A typical coaxial accelerometer cable consists of a central conductor, a dielectric (insulating) layer, and an outer braided shield.
When the cable is flexed, the dielectric and the outer shield rub against and separate from each other, generating a small static charge. That charge appears as a voltage across the cable’s capacitance, and the highly sensitive amplifier connected to the sensor — whether an external charge amplifier or the internal electronics of an IEPE accelerometer — faithfully records it. The result is a low-frequency “rumble” or a spurious voltage spike riding on top of the real vibration signal.
3. Characteristics of Triboelectric Noise
Triboelectric noise has a recognisable fingerprint, which is the key to telling it apart from a genuine machine fault:
- Low frequency: it is predominantly a low-frequency phenomenon, typically occurring below 10 Hz.
- Spurious spikes: it often appears as random, high-amplitude spikes in the time waveform that coincide with cable movement.
- “Ski-slope” spectrum: in an FFT spectrum it raises the noise floor sharply at the very low-frequency end and then falls away with increasing frequency, producing the classic downhill “ski-slope” shape. (This same shape can also arise from integration or sensor settling, so the cause must be confirmed.)
- Not repeatable: the noise is not synchronous with shaft rotation and does not repeat between successive measurements — unlike a true fault, which returns run after run.
4. Why It Is a Problem
Triboelectric noise lives in exactly the frequency band where some of the most important diagnostic information sits. It can mask the real low-frequency signals from a machine, which is especially damaging on slow-speed equipment where the key fault signatures — unbalance and misalignment at the 1× running speed — already fall near or below 10 Hz. The noise can either hide these genuine components or be mistaken for them, and either way it leads straight to a misdiagnosis: a healthy machine flagged as faulty, or a real fault buried under a false floor. Because high-pass signal filtering would also remove the very low-frequency data you are trying to keep, the noise must be prevented at the source rather than filtered out afterwards.
5. How to Prevent Triboelectric Noise
Triboelectric noise is one of the most preventable measurement errors in vibration work. It is controlled through correct cable selection and, above all, careful installation:
- Use high-quality, low-noise cable. Reputable sensor manufacturers offer dedicated “low-noise” cable that carries a conductive graphite layer between the dielectric and the outer shield. This layer acts as a drain, bleeding away static charge before it can build up and dramatically reducing the triboelectric effect.
- Secure the cable. This is the single most important practical step. Tie or glue the cable firmly to the machine surface as close to the sensor as possible, so that it vibrates with the machine instead of flexing and whipping independently. Loose loops and dangling sections are prime noise sources — good cable management is part of good sensor mounting.
- Avoid cable impacts. Route the cable away from rotating shafts, fan blades, and any other moving parts that could strike or whip it.
- Ground correctly. Although grounding does not address the triboelectric effect directly, following the manufacturer’s grounding instructions for the sensor and cabling prevents other electrical-noise problems such as ground loops, keeping the overall signal clean.
With the correct cable and — most importantly — a properly secured run, the effects of triboelectric noise can be almost completely eliminated, yielding cleaner and more reliable low-frequency vibration data. The same discipline pays off when you move from condition monitoring into active correction: when a portable analyser such as the Balanset-1A measures 1× amplitude and phase for field balancing, a noise-free low-frequency signal is exactly what the phase calculation depends on.
