Search results for query: *

Thanks for your input guys, great read. Yes I'm using FFT and checking amplitudes at frequency. My software also produces RMS for velocity and acceleration so its good to see how this plays out.

Thanks. My research indicates it typically follows the curve attached. My guess is that vibration levels increasing by 50% from the "as new" or "normal" condition indicates some form of failure is occurring. I thought 50% would be a good starting point as failure has an exponential...

Hi I've been using accelerometers to monitor bearing behavior on a small micro gas turbine. The sensors are mounted on the outer casing perpendicular to the shaft axis to measure vibrations at bearing locations. I'm getting consistent results for measuring the vibration levels at various RPM...

Well I was able to replicate Multi-Instrument Pro's function by applying the method as originally stated; take the FFT of both signals multiply one with conjugate of the other (element-wise multiplication) do the inverse FFT Plotting the Inverse FFT result vs time Delay produces the same...

So I tried simulating my results using Multi-Instrument Pro (https://www.virtins.com/multi-instrument.shtml) I can generate essentially the same results for the Phase Spectrum. However, Multi-Instrument has a great Cross-Correlation function which calculates the delay between Signal 1 & Signal...

Hi Greg Just implemented the complex spectrum of the transfer function and plotted phase vs frequency. It seems to work OK if the two signals are sine waves. However one is a sine wave and the other is a square wave (i.e. pulse of 5% duty cycle). It seems to give noisy readings that seem to...

Thanks, Greg, I appreciate the guidance. Will let you know how it goes. cheers DM

Hi Greg I currently use http://www.mitov.com/products/signallab#components to perform many DSP functions. There are components in this library that allow FFT operations however, I'm still not clear how to extract the phase difference between 2 audio signals as discussed above? cheers DM

Yeah. Is there a way to get accurate phase difference measurements then?

Hi Greg Can I please clarify by what you mean when the delay is meaningless where there is little signal? Is there are a better process for measuring phase difference when the signals are small and somewhat noisy? regards DM

Yeah, it's a bit frustrating. I couldn't find anything specific to cross-correlation in that library. From what I understand, this process can be used; take the FFT of both signals multiply one with conjugate of the other (element-wise multiplication) do the inverse FFT get max value as a...

https://numerics.mathdotnet.com/api/MathNet.Numerics.Statistics/Correlation.htm

Hi guys I'm trying to implement a phase shift meter in VB.NET between 2 audio signals. I'm using Math.NET cross-correlation functions however they can't calculate the phase shift or lag between the 2 signals as far as I can tell. Can anyone recommend a .NET DSP library that can calculate phase...

Hi all Well conducted some further testing today by restraining motion along the shaft axis. I noticed that the waveforms improved much more and I was able to get closer to my target quality limit 0.04 to 0.06 mm.gram. As mentioned by Greg the flexibility in the sway bars makes a difference...

Thanks for the links Walt, will look into it. Great references! cheers DM

Low noise MEMS are available almost to the same noise levels as piezos. In my case the residual waveform is much higher than signal noise, hence the issue is predominantly mechanical. If ISO 1940 isn't applicable, then what is? How do the commercial balancers such as the one shown above achieve...

Hi guys Thanks for your help. This is what I know so far; * Balancing speed is 3000 RPM, yes operational speed is 100k RPM * Bearings in the attached image have been replaced by quality Japanese close cage bearings that have virtually no play in the inner race. * Noise levels in the system are...

Hi Greg Its a soft bearing balancing cradle. Its mean't to be flexible enough to allow the rotating mass to move freely like the one shown in the image. In the commercial system, I noticed that the rotor has axial stops, I wonder if that makes a difference? thanks DM

Hi all I'm currently balancing micro-turbine rotors using 2 plane balancing method. ISO1940 G2.5 requires a quality balance limit of 0.033mm.gram per bearing location in my case (100,000rpm), which I'm finding near impossible. Is ISO1940 limits a bit of an overkill? The best I can physically...

Hi Tmoose, Yes I'm verifying residual unbalance in the tolerance planes. Its a home made setup with custom electronics and soft bearing rig. I've calibrated the setup using trial weights and then using influence coefficients to calculate residual unbalance as a direct readout. I have a copy of...