Understanding Tracking Filters

ডিভাইস

Portable balancer & Vibration analyzer Balanset-1A

€1,975.00 + ভ্যাট (যদি প্রযোজ্য হয়)

অংশ

Vibration sensor

€90.00 + ভ্যাট (যদি প্রযোজ্য হয়)

অংশ

Optical Sensor (Laser Tachometer)

€124.00 + ভ্যাট (যদি প্রযোজ্য হয়)

ডিভাইস

Balanset-4

€6,803.00 + ভ্যাট (যদি প্রযোজ্য হয়)

অংশ

Magnetic Stand Insize-60-kgf

€46.00 + ভ্যাট (যদি প্রযোজ্য হয়)

অংশ

Reflective tape

€10.00 + ভ্যাট (যদি প্রযোজ্য হয়)

ডিভাইস

Dynamic balancer “Balanset-1A” OEM

€1,735.00 + ভ্যাট (যদি প্রযোজ্য হয়)

A tracking filter — also called an order-tracking filter or synchronous filter — is a narrow band-pass filter used in vibration analysis instruments that automatically slides its centre frequency to follow a chosen multiple, or order, of the machine’s rotational speed. A “1× tracking filter,” for example, continuously locks onto the running-speed frequency, rejecting everything else and passing only the fundamental 1× component; a 2× or 3× filter follows twice or three times running speed in the same way. Because the filter rides the speed rather than sitting at a fixed frequency, it can measure the amplitude and phase of a synchronous component even while the machine accelerates or coasts down. That makes tracking filters essential for variable-speed equipment, for startup and coastdown transients, and for isolating individual order components within order analysis.

1. How a Tracking Filter Works

The basic principle

1. Speed reference: a tachometer বা keyphasor supplies a once-per-revolution pulse.
2. Frequency calculation: the instrument derives the instantaneous rotational frequency from the timing of those pulses.
3. Order multiplication: it multiplies that frequency by the chosen order number — 1, 2, 3, and so on.
4. Filter centring: a narrow band-pass filter is centred on the resulting frequency.
5. Continuous adjustment: as the speed changes, the filter’s centre frequency tracks it without interruption.
6. আউটপুট: a clean filtered signal containing only the selected order.

The defining trick is that the filter is slaved to the tachometer, so it always knows where the order of interest currently lives on the frequency axis — something a fixed filter can never do on a machine whose speed moves.

Filter characteristics

• Bandwidth: typically ±2–10% of the centre frequency.
• Narrowness: rejects neighbouring frequencies effectively.
• Tracking rate: able to follow rapidly changing speeds.
• Multiple filters: modern instruments can track several orders at once.

2. Applications

1. Startup and coastdown analysis

This is the headline application. As the machine runs up or coasts down through its speed range, a tracking filter follows the 1× component continuously:

• Track 1× amplitude and phase against speed during the transient — the same data captured during a run-up.
• Generate Bode plots of amplitude and phase versus speed.
• Identify critical speeds from the amplitude peaks.
• Estimate damping from the width of each resonance peak.
• Track 2× and 3× simultaneously to reveal multiple modes.

2. Variable-speed equipment

• Maintain order-based measurements despite a constantly moving speed.
• VFD-driven motors whose speed changes with the process.
• Wind turbines responding to gusting wind.
• Process equipment whose speed drifts with load.
• Consistent trending regardless of speed fluctuation, because everything is referenced to orders rather than fixed frequencies.

3. Balancing

• Track the 1× component throughout the ভারসাম্য procedure.
• Filter out non-1× content for a cleaner reading.
• Take the phase measurement at the 1× frequency only.
• Improve accuracy by rejecting unrelated vibration sources.

4. Order-specific analysis

• Isolate a particular order for detailed study.
• Track 2× to monitor the progression of misalignment.
• Follow the blade passing order in fans and pumps.
• Separate frequency components that would otherwise overlap.

3. Advantages of Tracking Filters

Speed independence

• Measurements stay meaningful no matter how the speed varies.
• Data from different speeds can be compared on the same order basis.
• Essential for any machine that does not hold a constant speed.

Component isolation

• Separates one order from every other frequency present.
• Yields cleaner signals than a full-spectrum FFT.
• Improves the signal-to-noise ratio for the order of interest.
• Enables precise amplitude and phase measurement of that order. This synchronous focus is conceptually allied to synchronous averaging, which also uses the tachometer to lift speed-locked components out of the noise.

Transient analysis

• Follows components straight through speed changes.
• Provides continuous measurement during acceleration and deceleration.
• Needs no steady-state condition.
• Reveals speed-dependent behaviour that a static measurement would miss.

4. Limitations and Considerations

It requires a tachometer

• An accurate speed reference is mandatory.
• The quality of the tachometer signal directly limits filter performance.
• It cannot be used on equipment without a speed reference.
• The once-per-revolution pulse must be reliable, or the tracking wanders.

It tracks only synchronous components

• Non-synchronous faults are not captured — including most bearing defects, which produce asynchronous vibration.
• Electrical-line frequencies are not tracked.
• Random and broadband vibration is filtered out.
• Complementary analysis is needed for a complete diagnosis.

Filter-bandwidth trade-offs

• Narrow filter: better rejection of adjacent frequencies, but slower to respond to speed changes.
• Wide filter: faster tracking, but may admit nearby components.
• Optimal: a 5–10% bandwidth suits most applications, balancing selectivity against tracking speed.

5. Tracking Filter versus FFT

A tracking filter and an FFT are complementary rather than competing tools. The FFT shows the whole spectrum at a fixed speed; the tracking filter follows one order through changing speed. The table summarises where each excels.

Feature	FFT Analysis	Tracking Filter
Speed requirement	Works at any speed	Requires a tachometer
Speed variation	Requires steady speed	Handles varying speed
Information	Full spectrum, all frequencies	Single order only
Non-synchronous faults	Detects all faults	Misses non-synchronous
Transient analysis	Difficult	Excellent
Best for	General diagnostics, steady-state	Critical-speed analysis, variable speed

6. Modern Implementations

Digital tracking filters

• Implemented in software inside modern analysers.
• Track multiple orders at once — 1×, 2×, 3× concurrently.
• Offer adjustable bandwidth.
• Display in real time during transients.

Integration with order analysis

• Tracking filters form the foundation of comprehensive order analysis.
• The full order spectrum is extracted, all orders together.
• Results appear as colour maps of order against speed, closely related to the waterfall and cascade displays.
• Critical speeds can be detected automatically from the order-tracking data.

7. Tracking Filters in Field Balancing

On a portable instrument the tracking filter is what keeps a balancing measurement honest when the speed will not hold perfectly steady. By passing only the 1× order and rejecting everything else, it gives the software a clean amplitude-and-phase vector to work from. The ব্যালানসেট-১এ uses exactly this approach: its tachometer pulse defines running speed, the synchronous 1× component is extracted in the machine’s own bearings at operating speed, and the resulting vector drives the trial-weight and correction calculations — and then confirms the residual vibration after correction. The tracking filter is the quiet mechanism that makes those numbers repeatable on real, slightly-unsteady machinery.

Tracking filters are specialised but powerful tools, especially for rotor dynamics and variable-speed equipment. By holding their focus on a chosen order while the speed moves, they enable transient analysis and speed-independent monitoring that ordinary FFT techniques cannot match — which is precisely why they remain central to critical-speed identification and advanced machinery diagnostics.

---

← প্রধান সূচিতে ফিরুন