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  1. JMarkWolf

    Rotating machinery imbalance

    Wow, that was a little like drinking from a fire hose! :) Who woke you guys up? :) The more I learn, the less I know. I have no expertise in this subject matter so I rely on others'. I purchased the embedded DFT, and my objective was to get some corroboration on the result report, and to...
  2. JMarkWolf

    Rotating machinery imbalance

    Greg wrote: "For first order I get an amplitude of 0.042V for the second channel" Need velocity in IPS please. Greg wrote: "energy correction" Huh? Greg wrote: "phase of 1.93 radians" Close, 1.93rads = 110.5 degrees. I show 113 degrees. Greg wrote: "Your data is very dirty"...
  3. JMarkWolf

    Rotating machinery imbalance

    Sorry. I had hastily edited and shortened this capture file. Now each channel has 2000 correlating samples. The enigmatic filename, CH13.csv was simply generated by my Tektronix scope (meaning channels 1 & 3). My embedded algorithm counts complete revolutions in the keyphasor channel and...
  4. JMarkWolf

    Rotating machinery imbalance

    Oops. Misunderstood how the upload works. My mistake. Should be there now.http://files.engineering.com/getfile.aspx?folder=0980ebfa-b9c4-44df-9de6-afa15ec6000b&file=ch13.csv
  5. JMarkWolf

    Rotating machinery imbalance

    Greg Locock said "The guts of the maths, if you have phase information, is a two liner from memory." Hi Greg I'd like to hear anything you can recall about this.
  6. JMarkWolf

    Rotating machinery imbalance

    After checking repost, data is indeed attached with "little paper clip" icon. We'll see if it remains this time.
  7. JMarkWolf

    Rotating machinery imbalance

    After posting last evening, data was attached, but is absent this morning. Attempting again.
  8. JMarkWolf

    Rotating machinery imbalance

    The data format is an Excel file, one column for the key phasor strobe and one column for the raw accel data. The 30 degree discrepancy appears to be quite repeatable. I suspect it has to do with the integrated Bessel filter in the MEMS accelerometer used to capture one data set, vs. the ICP...
  9. JMarkWolf

    Rotating machinery imbalance

    Hi Walter We have talked in the past. Yes this is correct. I have a commercial balancer (which may or not need calibration) with which to compare the results from my embedded algorithm, and the reports are very close, within 30 degrees and 0.02ips, repeatable with real-time acquisition from my...
  10. JMarkWolf

    Rotating machinery imbalance

    Rotating machinery, as in airplane propellers and helicopter rotors, determining magnitude of imbalance (velocity) and location of heavy spot (phase). I have in-flight time-series accelerometer and key-phasor data collected from aircraft. My embedded DFT is giving me a report as to above...
  11. JMarkWolf

    Rotating machinery imbalance

    Forgive my multiple posts but I have been directed to a couple different forums to better answer my question. I have an embedded DFT that identifies the velocity magnitude and phase of the heavy spot on rotors, from time-series accelerometer and key-phasor data. I wish to validate and...
  12. JMarkWolf

    Rotating machinery imbalance

    Near Detroit.
  13. JMarkWolf

    Rotating machinery imbalance

    I have nearly completed a hand-held device for capturing accelerometer time-series and key phasor data, for generating velocity magnitude and phase report of the "heavy spot" on rotating machinery. I now need to validate and eventually certify the result from my embedded DFT. Can someone refer...
  14. JMarkWolf

    Themocouple in noisy environments

    I neglected to mention that I have series ferrite beads and caps to ground on each thermocouple conductor.
  15. JMarkWolf

    Themocouple in noisy environments

    Update: As Retred points out, the low impedance apparently effectively nullifies the noise. I had acceptable results with two different circuit types: 1. a discrete differential op-amp circuit and 2. an integrated cold-junction compensated chip (MAX6675) Aside from a gain error induced by...
  16. JMarkWolf

    Themocouple in noisy environments

    K-type thermocouples are commonly used for exhaust gas (EGT) and cylinder head (CHT) temperature monitoring in automotive and aviation applications. The sensors are commonly "grounded" at the thermocouple junction, through the screw-in plug (EGT) and spark plug ring (CHT), directly to the engine...
  17. JMarkWolf

    Understanding Dynamic balancers

    Thanks sms This is the procedure I have been following, but no joy. Will persevere. Kelly Heroes, by the way, is a great movie. Always got a grin at Sutherlands 1950's era beatnik character in a 1940's period piece, however.
  18. JMarkWolf

    Understanding Dynamic Balancers: redux

    thruthefence wrote: "With some balancers I'm familiar with, working on aircraft, not experimentally, you would make a weight change, & observe the "move line" the weight change caused. If it didn't head right thru the center of the "clock", then you had a process called "correcting the clock...
  19. JMarkWolf

    Understanding Dynamic balancers

    Tmoose wrote: "I'm guessing the photo tach reads a rotating shaft surface that you have to prepare with zones of contrasting light/darkness/shiny-ness. One of the transitions is "zero" degrees" This is correct. A piece of strategically placed reflective tape is used to trip the photo-sensor...
  20. JMarkWolf

    Understanding Dynamic balancers

    I have a dynamic balancer I borrow from time to time, with which I balance the rotors on my helicopter. It is a small hand-held self-contained unit to which you attach an accelerometer and a photo tach. After a data acquisition cycle, it will report the velocity of the imbalance and the phase...

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