Measurement system

Low speed, highest precision: ACMT bearing and gear measuring technology

Low speed, highest precision: ACMT bearing and gear measuring technology
Low speed, highest precision: ACMT bearing and gear measuring technology
Low speed, highest precision: ACMT bearing and gear measuring technology

ACMT bearing and gear measurement technology: Precise data for the operational safety of your machines.

With the help of vibration measurement technology, the operating condition of machines can be reliably analyzed so that numerous faults can be detected at an early stage and rectified in good time. This makes vibration measurement technology a cost-effective and accurate method for measuring, analyzing and assessing the condition of machines.

Until now, however, it has been difficult to record the vibration pulses required for accurate evaluation in the necessary quantity, even on slow-running machines such as rolling mills, paper machines and transport mechanisms - because this requires a much longer measurement period than on high-speed machines, where the signals follow each other much more quickly. The data volumes that would be generated by such a time-consuming measurement would be correspondingly large and almost impossible to handle.

The solution to this problem is found in the VE 100 and VE 200 mobile vibration measuring devices from Vibroengineering and is called ACMT (Adash Compressed Measurement Time). This innovative measurement method allows the amount of data to be compressed without falsifying the measurement result. This makes ACMT the ideal method for using the many advantages of vibration measurement technology now also on low-speed machines!

You too can use this method to reliably monitor the operating status of your low-speed machines and avoid costly defects. The VE 100 and VE 200 devices are offered directly with a compact and comprehensible diagnostic software the Vibroengineering Diagnostic Center as a complete solution.

Functionality and application of ACMT

There are various processes that generate short pulses in slow speed machines. These pulses are often caused by rolling element bearings, gear wear, etc. It is important to be able to accurately detect and analyze these pulses to enable correct diagnosis.

However, the individual pulse can have a very short duration. Therefore, it is necessary to set a high sampling frequency for the measurement. This is the only way to ensure correct detection of the signal amplitude. However, the time interval between pulses can be very long at low speed (seconds, minutes). However, since several pulses must be acquired for a correct evaluation, a corresponding measurement duration is required - therefore, a low sampling frequency must be used in this case in order to be able to process the accruing amount of data.

These two aspects lead to a conflict in the measurement setting:

  • 1. high frequency sampling must be used for pulse measurement because the measurement signal is very short, for example 100ms long. If the time interval between pulses is given in seconds, there is only a small chance to capture them.
  • 2. for long time recordings on low speed machines, a low sampling frequency is needed to get more pulses in one signal. But with such a sampling, the pulse cannot be measured accurately because the high frequencies (also pulses) are cut off by an anti-aliasing filter.

The solution is called ACMT

Because this method compensates the two actually contradictory requirements by double sampling the data. The high sampling frequency is used at the beginning. Afterwards, the data is compressed, which is why the measurement can be made in the length needed for an exact evaluation.

All measurements were carried out on a slow-running rolling bearing 23132-TOR, which rotates at 60 rpm (1 Hz). There is a defect on the outer ring of the bearing. The short pulses are generated during operation.

The signal is measured with a recording duration of 4 seconds. When using 2,048 samples (default value), a 200 Hz anti-aliasing filter is used. We record the signal without pulses. All useful information is cut off by a filter. The result is so without any indication of the bearing damage.

Now a sampling frequency of 19,200 Hz is used. But only 42 ms time signal can be measured. The time between the pulses is 114 ms. So you need luck to hit the pulse. The next measurement is made using the ACMT method. The long-term signal contains the required number of pulses and the peak of each one is detected.

But the ACMT method can do even more

Short-time pulses usually have a small amplitude. They are often modulated by the speed frequency. Using a standard measurement, the result looks like this: You see only the speed of the sine wave and no or small pulses filtered by anti-aliasing.

In the standard ACMT, the ACMT is used together with the bandpass filtering, which removes the sinusoidal oscillation of the speed from the signal. The total short pulses are held and the amplitude is modulated for better overview. This result is much better because the scale of the Y-axis corresponds to the actual pulse amplitude, not the sine wave amplitude of the speed.

The distribution of the Vibroengineering products is done by Avibia GmbH in Engelskirchen and dbVibro in Alsbach.

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