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Home > Products > Product and Process Monitoring > Total Vu™ HMI > Total Vu™ FFT and SRL

Total Vu™ HMI - Fast Fourier Transforms (FFT) and Structural Return Loss (SRL)


FFT allows users to analyze periodic deviations in a measurement, such as the diameter of a wire or cable. By combining the FFT information with specifications for line speed, Total Vu™ software can identify likely causes of the measurement deviation, such as a faulty pulley. FFT can identify patterns that are not otherwise discernible, even when viewing trend charts. It is an essential tool in any process improvement effort.

Sometimes the value of FFT is best understood by evaluating it in your process. Contact us to get a free trial of this powerful tool.

Fourier analysis is applied to a set of samples (measurements) taken at regular intervals, to transform time-domain information (the measurement values) into frequency-domain values, where periodic changes in the input signal are seen as spikes in the frequency-domain graph.

Skilled operators can interpret the graphs and make decisions to take corrective action and improve the process. However, to simplify the decision making process, the FFT module in Total Vu software converts the spikes to measurement values, allowing the system to automatically alert the operator about potential process problems.

Total Vu software supports any number of FFT input measurements. This enables the user to tailor the resolution of the frequency analysis and view the resulting frequency-domain graph for each measurement.

The user may also select any FFT data point to see its magnitude, the harmonic frequencies associated with it, and the diameter of the pulley that might be responsible for the deviation.

Structural Return Loss in Communication Cable

SRL is an option of the FFT package that is of particular interest to the wire and cable industry.

Periodic fluctuations in wire and cable dimensions can cause significant signal loss, especially in high-frequency products such as network patch cables. Because periodic disturbances in a cable cause a portion of the signal to be reflected, overall signal transmission at various frequencies is degraded due to destructive interference between the reflected signal and the original signal.

By analyzing the periodic deviation of certain measurements, such as insulated wire diameter, the software can compute the signal loss that will occur at various frequencies along the length of a cable.

Monitoring SRL during production makes it possible to correct problems much faster. Prompt correction of problems helps you reduce scrap and improve production line throughput.

Total Vu software offers SRL calculation, and displays the SRL values (dB) in a graph correlating transmission frequency with signal loss at that frequency. As with the FFT graph, users can select an SRL data point to see its transmission frequency, signal loss, and the harmonics associated with the selected frequency.

As with FFT, “peak” values from SRL calculations, both frequency and amplitude values, can be converted to measurements. These values can be automatically checked and actions taken to alert the operator when warranted.

The SRL Spectrograph shows a graphical representation of the signal loss that occurs at various transmission frequencies over the length of a product. On completion of each SRL computation, that information is linked to the position (length) within the product at which the signal loss was computed.

The chart includes a configurable color spectrum to indicate the signal loss magnitude for a given length/frequency pair. An operator can quickly assess whether any portion of the cable is expected to show significant signal loss at one or more frequencies; the software also supports graphical zooming to examine areas of potential problems in greater detail. Because the spectrograph display is cumulative, it provides an excellent historical record of the SRL information acquired over the entire run of a product.

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