Attention everyone, certain vibration analyzers come equipped with a coherence parameter. I am curious to learn if this measurement can be utilized when encountering unknown frequencies in machinery or other components to determine their relationship with rotational frequencies. How can this parameter assist in diagnosing vibration issues? Please share your insights and experiences. Best regards.
Coherence is a crucial metric that examines the correlation between input and output data, serving as a key indicator of the relationship between the two. This function is commonly employed in frequency transfer functions, impact tests, and other analyses to assess the accuracy and reliability of collected data. Gary.
Thank you for your assistance, sir. I have noticed a high level of vibration on the pump's skid rather than its body. Would it be possible to place the output channel on the skid and the input channel on the pump body to determine the extent of vibration on the skid in relation to the body? Best regards.
Yes, you can analyze the transfer function of sliding (also known as skidding) in comparison to the pump housing. Coherence, in this context, signifies the level of correlation between the input and output variables. For example, if you measure a coherence value close to 1 between the skid and the pump, it indicates a consistent relationship between the two. However, it may not necessarily provide practical insights or aid in problem-solving. As mentioned by Gary, coherence is commonly utilized in impact and modal testing to ensure the accuracy of cause-and-effect relationships, such as impact leading to a specific response. In instances where there is a significant disparity between the skid and pump, it could point towards issues like loose bolting. This explanation is subject to further discussion and elaboration by other experts. Regards, Jim P.
In the document found at http://www.calpoly.edu/~cbirds...ng%20%20Analysis.pdf, the concept of comparing signals between two sensors is discussed on page 11. When analyzing frequency coherence between sensor A and sensor B, a coherence value of .95-1.0 indicates that the frequencies are the same, while a coherence value of .6 to 0 suggests different frequencies. A peak in the Frequency Response Function (FRF) plot signifies a natural frequency, characterized by a 180-degree phase shift and high coherence value close to 1.0. This information can be useful in determining the similarities or differences in signals from different sensors. - Dave
Thank you, Dave, for sharing valuable insights.
Absolutely, the coherence parameter in a vibration analyzer can indeed provide valuable insight when dealing with unknown frequencies. Essentially, coherence is a measure of how much a given frequency in the input is related to the output. Therefore, if you have an unknown frequency which appears to be causing trouble, you can use the coherence function to see if this frequency has any bearing on the rotational frequency of your machinery. If coherence is high, there may well be an intrinsic link between this unknown frequency and machinery operation. If it's low, the frequency might be a symptom of external disturbances or merely coincidental. In my experience, such analysis has often been beneficial in not only tackling unanticipated vibration issues but also predicting potential ones.
Absolutely, the coherence parameter is a very useful tool for diagnosing vibration issues. However, it's important to remember that it's measuring the linear relationship between two signals in the frequency domain. So, it's very helpful in understanding whether a specific vibration is related to rotational frequency or not. If there's a strong coherence, it means that there's a strong linear relationship - in other words, the vibration is likely related to that rotational frequency. But if the coherence is weak, the vibration might not be tied to that specific rotational frequency and could be due to some other variable in your machinery. Remember, it's just one tool in the toolkit for diagnosing these issues.
Absolutely, the coherence parameter can be incredibly helpful in diagnosing vibration issues. It provides a correlation between the input and output of a system by essentially showcasing how much of the output is directly influenced by the input at a specific frequency. When you're working with unknown frequencies in machinery, this can allow you to identify whether they're causally linked to the rotational frequencies, or if they're simply a result of external or unrelated internal factors. In my experience, it removes quite a bit of guesswork, especially with complex machinery.
Great question! The coherence parameter is super useful for identifying the relationship between vibration signals and rotational frequencies, especially when dealing with unknown frequencies. It helps establish whether the vibrations are related to a specific source or if they are random noise. By analyzing the coherence of different frequency components, you can pinpoint the dominant harmonics linked to machine operation, which can lead you to potential issues like imbalance or misalignment. In my experience, this approach has often illuminated otherwise hidden problems, allowing for more targeted maintenance.
Great question! The coherence parameter is really valuable for analyzing vibrations, especially when dealing with unknown frequencies. It helps determine how well the measured signal correlates with the input signal, which can indicate whether a frequency is directly related to a machine's operational behavior or if it's just noise. By examining coherence, you can pinpoint specific rotational frequencies and assess if any anomalies are actually affecting machine performance, thus aiding in diagnosing potential issues quickly and effectively. I've found it especially useful in condition monitoring to distinguish between genuine fault frequencies and harmless background vibrations. Would love to hear about others' experiences with this!
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Answer: What is coherence measurement in the context of vibration analysis? Answer: Coherence measurement in vibration analysis refers to the degree of correlation between two signals. It indicates how well one signal can be predicted from another, helping to understand the relationship between different frequencies in machinery.
Answer: How can coherence measurement help in identifying unknown frequencies in machinery? Answer: Coherence measurement can assist in identifying unknown frequencies by showing the strength of the relationship between different signals. When encountering unknown frequencies, analyzing coherence can help determine their correlation with known rotational frequencies, aiding in diagnosing vibration issues.
Answer: What role does the coherence parameter play in diagnosing vibration issues? Answer: The coherence parameter provides valuable insights into the relationship between various frequencies in machinery vibrations. By analyzing coherence, engineers can better understand the sources and characteristics of vibrations, helping to diagnose issues such as imbalances, misalignments, or structural defects.
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