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How to analyze change in frequency?

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  • A6intruder@myo-p.com
    I have a long term project which will seek to measure the degree of torsional resonance that exists at the flywheel of my car engine. I have a Hall effect
    Message 1 of 23 , Mar 1, 2013
      I have a long term project which will seek to measure the degree of
      torsional resonance that exists at the flywheel of my car engine. I have a
      Hall effect sensor mounted to sense the flywheel gear teeth going by the
      sensor. As the engine goes under load the power pulses actually cause
      minute changes in the frequency of those gear teeth going past the sensor.
      On a V-8 engine there are four power pulses per revolution of the flywheel.
      As the engine loads up and the power pulses get larger this minute change in
      frequency four times per revolution will grow in amplitude. If the
      mechanical drive system (engine & transmission) hit a point of rotational
      resonance those minute changes in frequency will become significantly
      larger.

      So my question is basically how do I analyze this frequency?

      I have a regular oscilloscope. I could monitor the basic waveform but how
      would I detect the minute change of frequency? Would the waveform shrink
      and expand if I get the time base just so?

      If has been 30 years since college calc classes, am I seeking a derivative
      or integral of the basic frequency? Can I achieve this with a certain mode
      on the oscilloscope (I 'm a very basic scope dope)?

      Ideally once I learn the terms and analysis I am trying to achieve I would
      want to collect this data during operation and record it on my laptop and
      sync it to the engine parameter data that I am already able to
      collect/record.

      What are the right terms/process I am looking for?

      The sensor is already mounted in the car.

      Data sheet:
      http://media.digikey.com/pdf/Data%20Sheets/Hamlin%20PDFs/55505.pdf

      I thought John Popelish or someone else in the group gave me the right
      process a few years ago but I couldn't find that post in the archives just
      now.

      Thanks,

      Dan Nicoson
    • Jan Kok
      A couple of questions: How many teeth are there on the gear that the sensor senses? And, is there some way to tell where the 0 position of the flywheel is? I
      Message 2 of 23 , Mar 1, 2013
        A couple of questions: How many teeth are there on the gear that the sensor
        senses? And, is there some way to tell where the "0" position of the
        flywheel is?

        I would suggest buying or borrowing a digital storage oscilloscope with a
        large memory (say 1 million samples or so) that can store waveform data to
        a USB key.

        Capture a bunch of waveforms from the sensor, and analyze them at your
        leisure on your computer.

        You'll get a frequency modulated square wave from the sensor. The higher
        the RPMs, the higher the frequency and the shorter the period of the square
        wave.

        Write a program to measure the period of each pulse, and plot the
        frequencies of the pulses (inverse of periods). You can use the Excel graph
        wizard to plot your data.

        Does the graph of the frequencies look somewhat sinusoidal? That graph
        would show the frequency modulation of the sensor square wave, and the
        cycles in the sinusoid should correlate with the power strokes of the
        pistons. The sinusoid should have much larger amplitude when the engine is
        under load.

        The amplitude should also be larger at certain RPMs where there is
        rotational resonance, compared with RPMs where there is no resonance.
        However, my hunch is that it will be hard to see any resonance, for several
        reasons: the resonant frequency may be higher than the sensor squarewave
        frequency, friction in the engine and drivetrain will act to dampen any
        resonance, and the resonance may be buried in random noise.

        Sounds like a fun project. I'll be curious to hear how it turns out.


        [Non-text portions of this message have been removed]
      • jeremy youngs
        as a certified master technician we use accelerometers and electronic vibration analzers for noise vibration and harshness concerns. i really am uncertain
        Message 3 of 23 , Mar 1, 2013
          as a certified master technician we use accelerometers and electronic
          vibration analzers for noise vibration and harshness concerns.
          i really am uncertain about the specifics of your investigation , the
          question is what is your goal?
          to lovate the frequency you have to know what component you are looking for
          . then what is the magnitude of the vibration ( i.e 1 g is going to be
          something heavy. is it a first second or third order vibration?

          or are you simply wanting to quantify the torque impulse and it f of o?
          in essence im pretty handy and trained with this by two manufacturers but i
          need more info as to what you are after.
          I presume that you are looking at crankshaft acceleration to try to
          calculate the impulse frequency?
          are you looking for a specific vibration? is there a concern with the auto
          or are you just researching dynamic phenomena ?

          --
          jeremy youngs


          [Non-text portions of this message have been removed]
        • jeremy youngs
          lovate = calculate !!!! fat fingers and tired eyes :) -- jeremy youngs
          Message 4 of 23 , Mar 1, 2013
            lovate = calculate !!!!
            fat fingers and tired eyes :)

            --
            jeremy youngs
          • A6intruder@myo-p.com
            Jan, The gear in question is the starter ring on the engine flywheel, so no real way to find a zero point on a rotation. I don t actually see a reason to
            Message 5 of 23 , Mar 2, 2013
              Jan,

              The gear in question is the starter ring on the engine flywheel, so no real
              way to find a "zero" point on a rotation. I don't actually see a reason to
              find a zero since we are looking for the change in frequency not a specific
              position in the rotation.

              The gear has 157 teeth and the operational range is 650 RPM to about 5500
              RPM, that makes our base frequency range 1700hz to 14,391hz. I am hoping to
              eventually analyze and display/record the level of torsional resonance in
              real time. I know there are IC's that convert frequency to voltage, in this
              case we need to convert the change in frequency to a voltage...

              I am trying to figure out the basic sensor/processing/display/record process
              now on my car so that later I can use it to analyze another combination of
              engine/gearbox/load. I could end up with a toothed sensor on each segment
              of the combination looking for issues as I do the full range of testing.

              Thanks,

              Dan

              -----Original Message-----
              From: Electronics_101@yahoogroups.com
              [mailto:Electronics_101@yahoogroups.com] On Behalf Of Jan Kok
              Sent: Saturday, March 02, 2013 12:09 AM
              To: Electronics_101@yahoogroups.com
              Subject: Re: [Electronics_101] How to analyze change in frequency?

              A couple of questions: How many teeth are there on the gear that the sensor
              senses? And, is there some way to tell where the "0" position of the
              flywheel is?

              I would suggest buying or borrowing a digital storage oscilloscope with a
              large memory (say 1 million samples or so) that can store waveform data to a
              USB key.

              Capture a bunch of waveforms from the sensor, and analyze them at your
              leisure on your computer.

              You'll get a frequency modulated square wave from the sensor. The higher the
              RPMs, the higher the frequency and the shorter the period of the square
              wave.

              Write a program to measure the period of each pulse, and plot the
              frequencies of the pulses (inverse of periods). You can use the Excel graph
              wizard to plot your data.

              Does the graph of the frequencies look somewhat sinusoidal? That graph would
              show the frequency modulation of the sensor square wave, and the cycles in
              the sinusoid should correlate with the power strokes of the pistons. The
              sinusoid should have much larger amplitude when the engine is under load.

              The amplitude should also be larger at certain RPMs where there is
              rotational resonance, compared with RPMs where there is no resonance.
              However, my hunch is that it will be hard to see any resonance, for several
              reasons: the resonant frequency may be higher than the sensor squarewave
              frequency, friction in the engine and drivetrain will act to dampen any
              resonance, and the resonance may be buried in random noise.

              Sounds like a fun project. I'll be curious to hear how it turns out.


              [Non-text portions of this message have been removed]



              ------------------------------------

              Please trim excess when replyingYahoo! Groups Links
            • A6intruder@myo-p.com
              Jeremy, I am trying set up a system that will allow me to sense when rotational resonance occurs. Just as you are measuring rigid structures with vibrations
              Message 6 of 23 , Mar 2, 2013
                Jeremy,

                I am trying set up a system that will allow me to sense when rotational
                resonance occurs. Just as you are measuring rigid structures with
                vibrations looking for the frequency that causes that structure to resonate,
                I am looking to find where a given engine/geabox/load combination will have
                torsional resonance. Every rotational system will have at least one point
                of resonance - hopefully not in the operational range.

                The end goal is to figure out the basic sensor/processing/display/record
                process now on my car so that later I can use it to analyze another
                combination of engine/gearbox/load. I could end up with a toothed sensor on
                each segment of the combination looking for issues as I do the full range of
                testing.

                I know this technology already exists but it is priced for manufacturers
                that are developing drivelines for any number of automotive and industrial
                uses. That puts it out of my hobby price range. Thus the "DIY-with-help"
                approach.

                Thanks,

                Dan

                -----Original Message-----
                From: Electronics_101@yahoogroups.com
                [mailto:Electronics_101@yahoogroups.com] On Behalf Of jeremy youngs
                Sent: Saturday, March 02, 2013 1:31 AM
                To: Electronics_101@yahoogroups.com
                Subject: Re: [Electronics_101] How to analyze change in frequency?

                as a certified master technician we use accelerometers and electronic
                vibration analzers for noise vibration and harshness concerns.
                i really am uncertain about the specifics of your investigation , the
                question is what is your goal?
                to lovate the frequency you have to know what component you are looking for
                . then what is the magnitude of the vibration ( i.e 1 g is going to be
                something heavy. is it a first second or third order vibration?

                or are you simply wanting to quantify the torque impulse and it f of o?
                in essence im pretty handy and trained with this by two manufacturers but i
                need more info as to what you are after.
                I presume that you are looking at crankshaft acceleration to try to
                calculate the impulse frequency?
                are you looking for a specific vibration? is there a concern with the auto
                or are you just researching dynamic phenomena ?

                --
                jeremy youngs


                [Non-text portions of this message have been removed]



                ------------------------------------

                Please trim excess when replyingYahoo! Groups Links
              • A6intruder@myo-p.com
                OK, Just answering Jan and Jeremy got me thinking. Without looking at any data sheets let s say we have an IC that converts frequency to voltage. The Hall
                Message 7 of 23 , Mar 2, 2013
                  OK,

                  Just answering Jan and Jeremy got me thinking.

                  Without looking at any data sheets let's say we have an IC that converts
                  frequency to voltage. The Hall effect sensor puts out a square wave signal
                  with equal high and low durations. So each time the sensor waveform crosses
                  a certain voltage (say 2 volts) it allows the IC to determine frequency and
                  output the corresponding signal voltage.

                  With a completely smooth turning gear wheel at a steady RPM we will get a
                  very steady signal voltage. Any time the frequency starts to vary the
                  signal voltage will go up or down. In the case of four power pulses per
                  revolution the IC should see four areas of changing voltage in each rotation
                  of the gear wheel. If you hooked an oscilloscope to the output of this IC
                  you would see a steady horizontal line for a steady RPM with no power
                  pulses. With power pulses you would start to see those four areas of
                  changing voltage.

                  The peak amplitude of the changing voltages would signify the magnitude of
                  the resonance. Large resonance would be a faster change in frequency since
                  the mechanical amplitude of the disturbance has to happen in the same amount
                  of time...

                  I'm thinking out loud here. I need to dig into some data sheets and see how
                  fast these IC's really are...

                  Thanks,

                  Dan

                  -----Original Message-----
                  From: Electronics_101@yahoogroups.com
                  [mailto:Electronics_101@yahoogroups.com] On Behalf Of Jan Kok
                  Sent: Saturday, March 02, 2013 12:09 AM
                  To: Electronics_101@yahoogroups.com
                  Subject: Re: [Electronics_101] How to analyze change in frequency?

                  A couple of questions: How many teeth are there on the gear that the sensor
                  senses? And, is there some way to tell where the "0" position of the
                  flywheel is?

                  I would suggest buying or borrowing a digital storage oscilloscope with a
                  large memory (say 1 million samples or so) that can store waveform data to a
                  USB key.

                  Capture a bunch of waveforms from the sensor, and analyze them at your
                  leisure on your computer.

                  You'll get a frequency modulated square wave from the sensor. The higher the
                  RPMs, the higher the frequency and the shorter the period of the square
                  wave.

                  Write a program to measure the period of each pulse, and plot the
                  frequencies of the pulses (inverse of periods). You can use the Excel graph
                  wizard to plot your data.

                  Does the graph of the frequencies look somewhat sinusoidal? That graph would
                  show the frequency modulation of the sensor square wave, and the cycles in
                  the sinusoid should correlate with the power strokes of the pistons. The
                  sinusoid should have much larger amplitude when the engine is under load.

                  The amplitude should also be larger at certain RPMs where there is
                  rotational resonance, compared with RPMs where there is no resonance.
                  However, my hunch is that it will be hard to see any resonance, for several
                  reasons: the resonant frequency may be higher than the sensor squarewave
                  frequency, friction in the engine and drivetrain will act to dampen any
                  resonance, and the resonance may be buried in random noise.

                  Sounds like a fun project. I'll be curious to hear how it turns out.


                  [Non-text portions of this message have been removed]



                  ------------------------------------

                  Please trim excess when replyingYahoo! Groups Links
                • Kerry Wentworth
                  The MicroChip TC9400 will convert frequency to voltage. A bit pricey at ~$9, but it will do the job. Kerry
                  Message 8 of 23 , Mar 2, 2013
                    The MicroChip TC9400 will convert frequency to voltage. A bit pricey at
                    ~$9, but it will do the job.

                    Kerry



                    A6intruder@... wrote:
                    > Jan,
                    >
                    > The gear in question is the starter ring on the engine flywheel, so no real
                    > way to find a "zero" point on a rotation. I don't actually see a reason to
                    > find a zero since we are looking for the change in frequency not a specific
                    > position in the rotation.
                    >
                    > The gear has 157 teeth and the operational range is 650 RPM to about 5500
                    > RPM, that makes our base frequency range 1700hz to 14,391hz. I am hoping to
                    > eventually analyze and display/record the level of torsional resonance in
                    > real time. I know there are IC's that convert frequency to voltage, in this
                    > case we need to convert the change in frequency to a voltage...
                    >
                    > I am trying to figure out the basic sensor/processing/display/record process
                    > now on my car so that later I can use it to analyze another combination of
                    > engine/gearbox/load. I could end up with a toothed sensor on each segment
                    > of the combination looking for issues as I do the full range of testing.
                    >
                    > Thanks,
                    >
                    > Dan
                    >
                    > -----Original Message-----
                    > From: Electronics_101@yahoogroups.com
                    > [mailto:Electronics_101@yahoogroups.com] On Behalf Of Jan Kok
                    > Sent: Saturday, March 02, 2013 12:09 AM
                    > To: Electronics_101@yahoogroups.com
                    > Subject: Re: [Electronics_101] How to analyze change in frequency?
                    >
                    > A couple of questions: How many teeth are there on the gear that the sensor
                    > senses? And, is there some way to tell where the "0" position of the
                    > flywheel is?
                    >
                    > I would suggest buying or borrowing a digital storage oscilloscope with a
                    > large memory (say 1 million samples or so) that can store waveform data to a
                    > USB key.
                    >
                    > Capture a bunch of waveforms from the sensor, and analyze them at your
                    > leisure on your computer.
                    >
                    > You'll get a frequency modulated square wave from the sensor. The higher the
                    > RPMs, the higher the frequency and the shorter the period of the square
                    > wave.
                    >
                    > Write a program to measure the period of each pulse, and plot the
                    > frequencies of the pulses (inverse of periods). You can use the Excel graph
                    > wizard to plot your data.
                    >
                    > Does the graph of the frequencies look somewhat sinusoidal? That graph would
                    > show the frequency modulation of the sensor square wave, and the cycles in
                    > the sinusoid should correlate with the power strokes of the pistons. The
                    > sinusoid should have much larger amplitude when the engine is under load.
                    >
                    > The amplitude should also be larger at certain RPMs where there is
                    > rotational resonance, compared with RPMs where there is no resonance.
                    > However, my hunch is that it will be hard to see any resonance, for several
                    > reasons: the resonant frequency may be higher than the sensor squarewave
                    > frequency, friction in the engine and drivetrain will act to dampen any
                    > resonance, and the resonance may be buried in random noise.
                    >
                    > Sounds like a fun project. I'll be curious to hear how it turns out.
                    >
                    >
                    > [Non-text portions of this message have been removed]
                    >
                    >
                    >
                    > ------------------------------------
                    >
                    > Please trim excess when replyingYahoo! Groups Links
                    >
                    >
                    >
                    >
                    >
                    >
                  • Derek
                    Solution... Use a hall sensor to detect the teeth moving nearby. Capacitor couple and amplify the signal. You will then get pulses as each of the teeth go by.
                    Message 9 of 23 , Mar 2, 2013
                      Solution...

                      Use a hall sensor to detect the teeth moving nearby. Capacitor couple and amplify the signal. You will then get pulses as each of the teeth go by. Convert from frequency to voltage and then monitor the voltage.

                      Derek Koonce
                      DDK Interactive Consulting Services




                      --- In Electronics_101@yahoogroups.com, "A6intruder@..." <A6intruder@...> wrote:
                      >
                      > Jeremy,
                      >
                      > I am trying set up a system that will allow me to sense when rotational
                      > resonance occurs. Just as you are measuring rigid structures with
                      > vibrations looking for the frequency that causes that structure to resonate,
                      > I am looking to find where a given engine/geabox/load combination will have
                      > torsional resonance. Every rotational system will have at least one point
                      > of resonance - hopefully not in the operational range.
                      >
                      > The end goal is to figure out the basic sensor/processing/display/record
                      > process now on my car so that later I can use it to analyze another
                      > combination of engine/gearbox/load. I could end up with a toothed sensor on
                      > each segment of the combination looking for issues as I do the full range of
                      > testing.
                      >
                      > I know this technology already exists but it is priced for manufacturers
                      > that are developing drivelines for any number of automotive and industrial
                      > uses. That puts it out of my hobby price range. Thus the "DIY-with-help"
                      > approach.
                      >
                      > Thanks,
                      >
                      > Dan
                      >
                      > -----Original Message-----
                      > From: Electronics_101@yahoogroups.com
                      > [mailto:Electronics_101@yahoogroups.com] On Behalf Of jeremy youngs
                      > Sent: Saturday, March 02, 2013 1:31 AM
                      > To: Electronics_101@yahoogroups.com
                      > Subject: Re: [Electronics_101] How to analyze change in frequency?
                      >
                      > as a certified master technician we use accelerometers and electronic
                      > vibration analzers for noise vibration and harshness concerns.
                      > i really am uncertain about the specifics of your investigation , the
                      > question is what is your goal?
                      > to lovate the frequency you have to know what component you are looking for
                      > . then what is the magnitude of the vibration ( i.e 1 g is going to be
                      > something heavy. is it a first second or third order vibration?
                      >
                      > or are you simply wanting to quantify the torque impulse and it f of o?
                      > in essence im pretty handy and trained with this by two manufacturers but i
                      > need more info as to what you are after.
                      > I presume that you are looking at crankshaft acceleration to try to
                      > calculate the impulse frequency?
                      > are you looking for a specific vibration? is there a concern with the auto
                      > or are you just researching dynamic phenomena ?
                      >
                      > --
                      > jeremy youngs
                      >
                      >
                      > [Non-text portions of this message have been removed]
                      >
                      >
                      >
                      > ------------------------------------
                      >
                      > Please trim excess when replyingYahoo! Groups Links
                      >
                    • Donald H Locker
                      I once monitored the torsional vibration at the tail end of a dynamometer using the frequency from a 60-tooth wheel mounted there. The engine torque pulses
                      Message 10 of 23 , Mar 2, 2013
                        I once monitored the torsional vibration at the tail end of a dynamometer using the frequency from a 60-tooth wheel mounted there. The engine torque pulses were clearly visible in the signal. I used a frequency to voltage converter (this was many years ago :) probably an LM2907, and just watched the output on a slow oscilloscope sweep. Most data were analysed by hand.

                        Donald.
                        --
                        *Plain Text* email -- it's an accessibility issue
                        () no proprietary attachments; no html mail
                        /\ ascii ribbon campaign - <www.asciiribbon.org>

                        ----- Original Message -----
                        > From: A6intruder@...
                        > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                        > Sent: Saturday, March 2, 2013 9:48:13 AM
                        > Subject: RE: [Electronics_101] How to analyze change in frequency?
                        > Jan,
                        >
                        > The gear in question is the starter ring on the engine flywheel, so no
                        > real
                        > way to find a "zero" point on a rotation. I don't actually see a
                        > reason to
                        > find a zero since we are looking for the change in frequency not a
                        > specific
                        > position in the rotation.
                        >
                        > The gear has 157 teeth and the operational range is 650 RPM to about
                        > 5500
                        > RPM, that makes our base frequency range 1700hz to 14,391hz. I am
                        > hoping to
                        > eventually analyze and display/record the level of torsional resonance
                        > in
                        > real time. I know there are IC's that convert frequency to voltage, in
                        > this
                        > case we need to convert the change in frequency to a voltage...
                        >
                        > I am trying to figure out the basic sensor/processing/display/record
                        > process
                        > now on my car so that later I can use it to analyze another
                        > combination of
                        > engine/gearbox/load. I could end up with a toothed sensor on each
                        > segment
                        > of the combination looking for issues as I do the full range of
                        > testing.
                        >
                        > Thanks,
                        >
                        > Dan
                        >
                        > -----Original Message-----
                        > From: Electronics_101@yahoogroups.com
                        > [mailto:Electronics_101@yahoogroups.com] On Behalf Of Jan Kok
                        > Sent: Saturday, March 02, 2013 12:09 AM
                        > To: Electronics_101@yahoogroups.com
                        > Subject: Re: [Electronics_101] How to analyze change in frequency?
                        >
                        > A couple of questions: How many teeth are there on the gear that the
                        > sensor
                        > senses? And, is there some way to tell where the "0" position of the
                        > flywheel is?
                        >
                        > I would suggest buying or borrowing a digital storage oscilloscope
                        > with a
                        > large memory (say 1 million samples or so) that can store waveform
                        > data to a
                        > USB key.
                        >
                        > Capture a bunch of waveforms from the sensor, and analyze them at your
                        > leisure on your computer.
                        >
                        > You'll get a frequency modulated square wave from the sensor. The
                        > higher the
                        > RPMs, the higher the frequency and the shorter the period of the
                        > square
                        > wave.
                        >
                        > Write a program to measure the period of each pulse, and plot the
                        > frequencies of the pulses (inverse of periods). You can use the Excel
                        > graph
                        > wizard to plot your data.
                        >
                        > Does the graph of the frequencies look somewhat sinusoidal? That graph
                        > would
                        > show the frequency modulation of the sensor square wave, and the
                        > cycles in
                        > the sinusoid should correlate with the power strokes of the pistons.
                        > The
                        > sinusoid should have much larger amplitude when the engine is under
                        > load.
                        >
                        > The amplitude should also be larger at certain RPMs where there is
                        > rotational resonance, compared with RPMs where there is no resonance.
                        > However, my hunch is that it will be hard to see any resonance, for
                        > several
                        > reasons: the resonant frequency may be higher than the sensor
                        > squarewave
                        > frequency, friction in the engine and drivetrain will act to dampen
                        > any
                        > resonance, and the resonance may be buried in random noise.
                        >
                        > Sounds like a fun project. I'll be curious to hear how it turns out.
                        >
                        >
                        > [Non-text portions of this message have been removed]
                        >
                        >
                        >
                        > ------------------------------------
                        >
                        > Please trim excess when replyingYahoo! Groups Links
                        >
                        >
                        >
                        >
                        >
                        >
                        > ------------------------------------
                        >
                        > Please trim excess when replyingYahoo! Groups Links
                        >
                        >
                        >
                      • Jong Kung
                        Modern electronics ignition / fuel injected engines have crankshaft position sensors http://en.wikipedia.org/wiki/Crankshaft_position_sensor I don t know how
                        Message 11 of 23 , Mar 2, 2013
                          Modern electronics ignition / fuel injected engines have crankshaft position sensors

                          http://en.wikipedia.org/wiki/Crankshaft_position_sensor

                          I don't know how this will help the subject but I though I'll put it out there.


                          Jong

                          On Mar 2, 2013, at 4:48 AM, "A6intruder@..." <A6intruder@...> wrote:

                          > Jan,
                          >
                          > The gear in question is the starter ring on the engine flywheel, so no real
                          > way to find a "zero" point on a rotation.
                          >


                          [Non-text portions of this message have been removed]
                        • Aaron Turner
                          ... + 1 for the hall sensor idea. A lot of motorcycles figure out their timing by a hall sensor on the flywheel/stator rotor. -- Aaron Turner
                          Message 12 of 23 , Mar 2, 2013
                            On Sat, Mar 2, 2013 at 9:05 AM, Derek <derek@...> wrote:

                            > **
                            >
                            >
                            > Solution...
                            >
                            > Use a hall sensor to detect the teeth moving nearby. Capacitor couple and
                            > amplify the signal. You will then get pulses as each of the teeth go by.
                            > Convert from frequency to voltage and then monitor the voltage.
                            >

                            + 1 for the hall sensor idea. A lot of motorcycles figure out their timing
                            by a hall sensor on the flywheel/stator rotor.


                            --
                            Aaron Turner
                            http://synfin.net/ Twitter: @synfinatic
                            http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix &
                            Windows
                            Those who would give up essential Liberty, to purchase a little temporary
                            Safety, deserve neither Liberty nor Safety.
                            -- Benjamin Franklin
                            "carpe diem quam minimum credula postero"


                            [Non-text portions of this message have been removed]
                          • jeremy youngs
                            hall sensors, variable reluctance sensors, are all rotational speed tracking devices the only thing useful from these to be gained is crank position and phase
                            Message 13 of 23 , Mar 2, 2013
                              hall sensors, variable reluctance sensors, are all rotational speed
                              tracking devices the only thing useful from these to be gained is crank
                              position and phase
                              this will help but it is NOT all the input required an acceleometer is
                              absolutely essential to this application as is a transducer for measuring
                              the frquency of the specified noise/vibration/harhness (nvh) conern.
                              this is not a rogue path to follow without guidance as you have to know
                              WHAT you are searching for as ALL driveline noise is transmitted through
                              the crankshaft as they are all mechanically coupled
                              this pdf li nk should help
                              http://users.757.org/~ken/T/Toyota%20Training%20472%20-%20NVH.pdf
                              --
                              jeremy youngs


                              [Non-text portions of this message have been removed]
                            • Tim S
                              It sounds like Jeremy has a lot of experience with this type of stuff, but when reading it I immediately thought of using an FFT function on the scope to read
                              Message 14 of 23 , Mar 3, 2013
                                It sounds like Jeremy has a lot of experience with this type of stuff, but when reading it I immediately thought of using an FFT function on the scope to read out the frequency of the sensor signal directly. On my cheap $400 DSO, it has built in FFT functions. I would hook your sensor up to the scope, and then you could view both the fundamental and secondary frequencies directly on the scope. There may be some chips out there like certain DSP's that can do the FFT for you without the use of an expensive Digital Oscilloscope but I don't know any off hand.


                                --- In Electronics_101@yahoogroups.com, "A6intruder@..." <A6intruder@...> wrote:
                                >
                                > I have a long term project which will seek to measure the degree of
                                > torsional resonance that exists at the flywheel of my car engine. I have a
                                > Hall effect sensor mounted to sense the flywheel gear teeth going by the
                                > sensor. As the engine goes under load the power pulses actually cause
                                > minute changes in the frequency of those gear teeth going past the sensor.
                                > On a V-8 engine there are four power pulses per revolution of the flywheel.
                                > As the engine loads up and the power pulses get larger this minute change in
                                > frequency four times per revolution will grow in amplitude. If the
                                > mechanical drive system (engine & transmission) hit a point of rotational
                                > resonance those minute changes in frequency will become significantly
                                > larger.
                                >
                                > So my question is basically how do I analyze this frequency?
                                >
                                > I have a regular oscilloscope. I could monitor the basic waveform but how
                                > would I detect the minute change of frequency? Would the waveform shrink
                                > and expand if I get the time base just so?
                                >
                                > If has been 30 years since college calc classes, am I seeking a derivative
                                > or integral of the basic frequency? Can I achieve this with a certain mode
                                > on the oscilloscope (I 'm a very basic scope dope)?
                                >
                                > Ideally once I learn the terms and analysis I am trying to achieve I would
                                > want to collect this data during operation and record it on my laptop and
                                > sync it to the engine parameter data that I am already able to
                                > collect/record.
                                >
                                > What are the right terms/process I am looking for?
                                >
                                > The sensor is already mounted in the car.
                                >
                                > Data sheet:
                                > http://media.digikey.com/pdf/Data%20Sheets/Hamlin%20PDFs/55505.pdf
                                >
                                > I thought John Popelish or someone else in the group gave me the right
                                > process a few years ago but I couldn't find that post in the archives just
                                > now.
                                >
                                > Thanks,
                                >
                                > Dan Nicoson
                                >
                              • Howard Hansen
                                ... FFT will work when the engine is running at a steady speed. But FFT won t work when the engine is accelerating or there is a variable load on the engine.
                                Message 15 of 23 , Mar 3, 2013
                                  On 3/3/2013 7:22 AM, Tim S wrote:
                                  >
                                  >
                                  > It sounds like Jeremy has a lot of experience with this type of stuff,
                                  > but when reading it I immediately thought of using an FFT function on
                                  > the scope to read out the frequency of the sensor signal directly. On
                                  > my cheap $400 DSO, it has built in FFT functions. I would hook your
                                  > sensor up to the scope, and then you could view both the fundamental
                                  > and secondary frequencies directly on the scope. There may be some
                                  > chips out there like certain DSP's that can do the FFT for you without
                                  > the use of an expensive Digital Oscilloscope but I don't know any off
                                  > hand.
                                  >

                                  FFT will work when the engine is running at a steady speed. But FFT
                                  won't work when the engine is accelerating or there is a variable load
                                  on the engine.

                                  T^he other Howard

                                  >
                                  > --- In Electronics_101@yahoogroups.com
                                  > <mailto:Electronics_101%40yahoogroups.com>, "A6intruder@..." wrote:
                                  > >
                                  > > I have a long term project which will seek to measure the degree of
                                  > > torsional resonance that exists at the flywheel of my car engine. I
                                  > have a
                                  > > Hall effect sensor mounted to sense the flywheel gear teeth going by the
                                  > > sensor. As the engine goes under load the power pulses actually cause
                                  > > minute changes in the frequency of those gear teeth going past the
                                  > sensor.
                                  > > On a V-8 engine there are four power pulses per revolution of the
                                  > flywheel.
                                  > > As the engine loads up and the power pulses get larger this minute
                                  > change in
                                  > > frequency four times per revolution will grow in amplitude. If the
                                  > > mechanical drive system (engine & transmission) hit a point of
                                  > rotational
                                  > > resonance those minute changes in frequency will become significantly
                                  > > larger.
                                  > >
                                  > > So my question is basically how do I analyze this frequency?
                                  > >
                                  > > I have a regular oscilloscope. I could monitor the basic waveform
                                  > but how
                                  > > would I detect the minute change of frequency? Would the waveform shrink
                                  > > and expand if I get the time base just so?
                                  > >
                                  > > If has been 30 years since college calc classes, am I seeking a
                                  > derivative
                                  > > or integral of the basic frequency? Can I achieve this with a
                                  > certain mode
                                  > > on the oscilloscope (I 'm a very basic scope dope)?
                                  > >
                                  > > Ideally once I learn the terms and analysis I am trying to achieve I
                                  > would
                                  > > want to collect this data during operation and record it on my
                                  > laptop and
                                  > > sync it to the engine parameter data that I am already able to
                                  > > collect/record.
                                  > >
                                  > > What are the right terms/process I am looking for?
                                  > >
                                  > > The sensor is already mounted in the car.
                                  > >
                                  > > Data sheet:
                                  > > http://media.digikey.com/pdf/Data%20Sheets/Hamlin%20PDFs/55505.pdf
                                  > >
                                  > > I thought John Popelish or someone else in the group gave me the right
                                  > > process a few years ago but I couldn't find that post in the
                                  > archives just
                                  > > now.
                                  > >
                                  > > Thanks,
                                  > >
                                  > > Dan Nicoson
                                  > >
                                  >
                                  >



                                  [Non-text portions of this message have been removed]
                                • John Popelish
                                  ... I think an FFT could be made to work, but it would take a bit of up front computation. The sample period for the FFT would have to be exactly one or an
                                  Message 16 of 23 , Mar 3, 2013
                                    On 03/03/2013 04:37 PM, Howard Hansen wrote:
                                    >
                                    > FFT will work when the engine is running at a steady
                                    > speed. But FFT won't work when the engine is
                                    > accelerating or there is a variable load on the engine.

                                    I think an FFT could be made to work, but it would take a
                                    bit of up front computation.

                                    The sample period for the FFT would have to be exactly one
                                    or an integer multiple of rotations, and that would take
                                    tooth counting.

                                    The intervals tooth to tooth would have to be measured by
                                    some high frequency counter and then reciprocled to turn
                                    period into velocity samples, every tooth.

                                    Then that sequence of velocities of variable periods would
                                    have to be resampled, to make interpolated velocity samples,
                                    uniformly spaced in time, through one (or multiple rotations).

                                    At that point, a normal FFT could be calculated that would
                                    produce the magnitudes and phases of the harmonics of the
                                    rotational frequency.

                                    There may be a few mathematical short cuts possible, that
                                    would simply this process and still give useful results.
                                    I'm not a good enough FFT mathematician to see them, without
                                    a lot of digging.

                                    Fortunately, you don't need and really cannot use the FFT of
                                    every single rotation, so data could be taken for one
                                    rotation and then the FFT calculated during the next few
                                    rotations, with just tooth counting continuing, during that
                                    process, so the next FFT could start on the same tooth, to
                                    keep the phase information from jumping around. The running
                                    average of several of these results could produce a usably
                                    smooth display on some bar graph indicator.

                                    --
                                    Regards,

                                    John Popelish
                                  • jeremy youngs
                                    ... on this project though if you dont have a magnitude of impulse (accelerometer) or the frequency of vibration (transducer pick up) one will not be able to
                                    Message 17 of 23 , Mar 3, 2013
                                      >
                                      > john
                                      >


                                      > yes without going into the strategies and engine controller uses
                                      > quadrature encoding in the crank sensor to monitor instantaneous crankshaft
                                      > acceleration for misfire detection. which is exactly what you have outlined
                                      > here.
                                      >
                                      on this project though if you dont have a magnitude of impulse
                                      (accelerometer) or the frequency of vibration (transducer pick up) one
                                      will not be able to properly calculate the data for proper fourier analysis
                                      and will be lacking enough detail to have any substantial quantitative
                                      results , you can measure 0 drive train harmonics by traking rotation or
                                      acceleration ther is simply not enough information to calculate the other
                                      polynomial variables. Simply in order to do what the o.p is aking 3 sensors
                                      will be needed and the crank seneor would be very easy to just access at
                                      the engine controller by simple back probing. arduino shields are available
                                      with accelerometers and transducers availabe it is possible an electret
                                      with enough frequency spectrum would work as well.



                                      --
                                      jeremy youngs


                                      [Non-text portions of this message have been removed]
                                    • Jan Kok
                                      Regarding using a Hall effect sensor to measure rotational resonance: it may work if the resonant frequency is substantially lower than the frequency of the
                                      Message 18 of 23 , Mar 3, 2013
                                        Regarding using a Hall effect sensor to measure rotational resonance: it
                                        may work if the resonant frequency is substantially lower than the
                                        frequency of the square wave that you get from the Hall effect sensor. If
                                        the resonant frequency you're looking for is close to or higher than the
                                        frequency of the sensor square wave (and actually, if there are strong
                                        frequency components above the frequency of the square wave), then the Hall
                                        effect sensor won't give you reliable info about the frequency variations,
                                        i.e. small, high-frequency changes in the rotation rate.

                                        It has to do with sampling theory. Suppose you use an A/D converter to
                                        sample a 900 Hz sine wave at a 1000 samples per second rate. In 10 ms the
                                        sine wave goes through 9 cycles, and you take 10 samples. The result is
                                        that the samples, if plotted, look like a single cycle of a sine wave at
                                        100 Hz. So 900 Hz looks like 100 Hz after sampling. The signal you are
                                        sampling must not have frequency components greater than 1/2 the sampling
                                        frequency, in order to avoid seeing spurious frequencies in the sampled
                                        data.

                                        With the Hall effect sensor, you can sample on the rising and falling edges
                                        of the sensor square wave, and what you are sampling is the width of the
                                        pulses. If you get 500 Hz from the sensor, then you can sample 1000 times
                                        per second and the maximum resonant frequency you can see accurately is
                                        below half that rate, i.e. less than 500 Hz.



                                        On Sun, Mar 3, 2013 at 4:38 PM, jeremy youngs <jcyoungs76@...> wrote:

                                        > >
                                        > > john
                                        > >
                                        >
                                        >
                                        > > yes without going into the strategies and engine controller uses
                                        > > quadrature encoding in the crank sensor to monitor instantaneous
                                        > crankshaft
                                        > > acceleration for misfire detection. which is exactly what you have
                                        > outlined
                                        > > here.
                                        > >
                                        > on this project though if you dont have a magnitude of impulse
                                        > (accelerometer) or the frequency of vibration (transducer pick up) one
                                        > will not be able to properly calculate the data for proper fourier analysis
                                        > and will be lacking enough detail to have any substantial quantitative
                                        > results , you can measure 0 drive train harmonics by traking rotation or
                                        > acceleration ther is simply not enough information to calculate the other
                                        > polynomial variables. Simply in order to do what the o.p is aking 3 sensors
                                        > will be needed and the crank seneor would be very easy to just access at
                                        > the engine controller by simple back probing. arduino shields are available
                                        > with accelerometers and transducers availabe it is possible an electret
                                        > with enough frequency spectrum would work as well.
                                        >
                                        >
                                        >
                                        > --
                                        > jeremy youngs
                                        >
                                        >


                                        [Non-text portions of this message have been removed]
                                      • AlienRelics
                                        I believe he said the resonance he is looking for would be at 1/4 the rotational frequency. Why not measure the period between gear teeth, and compare how it
                                        Message 19 of 23 , Mar 3, 2013
                                          I believe he said the resonance he is looking for would be at 1/4 the rotational frequency.

                                          Why not measure the period between gear teeth, and compare how it changes? It seems to me that what you are looking for is FM impressed on the pulses from the gear teeth.

                                          Steve Greenfield AE7HD

                                          --- In Electronics_101@yahoogroups.com, Jan Kok <jan.kok.5y@...> wrote:
                                          >
                                          > Regarding using a Hall effect sensor to measure rotational resonance: it
                                          > may work if the resonant frequency is substantially lower than the
                                          > frequency of the square wave that you get from the Hall effect sensor. If
                                          > the resonant frequency you're looking for is close to or higher than the
                                          > frequency of the sensor square wave (and actually, if there are strong
                                          > frequency components above the frequency of the square wave), then the Hall
                                          > effect sensor won't give you reliable info about the frequency variations,
                                          > i.e. small, high-frequency changes in the rotation rate.
                                          >
                                          > It has to do with sampling theory. Suppose you use an A/D converter to
                                          > sample a 900 Hz sine wave at a 1000 samples per second rate. In 10 ms the
                                          > sine wave goes through 9 cycles, and you take 10 samples. The result is
                                          > that the samples, if plotted, look like a single cycle of a sine wave at
                                          > 100 Hz. So 900 Hz looks like 100 Hz after sampling. The signal you are
                                          > sampling must not have frequency components greater than 1/2 the sampling
                                          > frequency, in order to avoid seeing spurious frequencies in the sampled
                                          > data.
                                          >
                                          > With the Hall effect sensor, you can sample on the rising and falling edges
                                          > of the sensor square wave, and what you are sampling is the width of the
                                          > pulses. If you get 500 Hz from the sensor, then you can sample 1000 times
                                          > per second and the maximum resonant frequency you can see accurately is
                                          > below half that rate, i.e. less than 500 Hz.
                                          >
                                          >
                                        • jeremy youngs
                                          I believe he said the resonance he is looking for would be at 1/4 the rotational frequency. Why not measure the period between gear teeth, and compare how it
                                          Message 20 of 23 , Mar 3, 2013
                                            I believe he said the resonance he is looking for would be at 1/4 the
                                            rotational frequency.

                                            Why not measure the period between gear teeth, and compare how it changes?
                                            It seems to me that what you are looking for is FM impressed on the pulses
                                            from the gear teeth.

                                            Steve Greenfield AE7HD

                                            steve i believe accel decel curve could be extrapolated via demodulation
                                            as you suggest. however this would assume abunch of ommitted truths that
                                            need reconciliation. just a few i wil miss them as i dont wish to write a
                                            thesis here :)

                                            1 this meaure is taken at the flywheel

                                            2 what exactly are we looking for ? just the 8 impulses in 2 revolutions?

                                            ( the op hasnt been as forward on what he is looking to do here as would be
                                            required)

                                            3 there will be MANY resonances as anything attached to the crankshaft will
                                            have a natural resonant frequency

                                            4 there will be 1st and second order harmonics dominating this analysis

                                            some means of isolating the suspect resonance is needed ( also to note what
                                            IS the suspect resonance? this has not been defined !!!!)

                                            (without definition i cannot help lead to a resolution :)

                                            5 what are the particulars of the test method i e under load ? going down
                                            the road? idling in the driveway? these conditions will radically affect
                                            the identifying of suspect parameters and will lead to different results

                                            in short i think an arduino with accelerometer, transducer and ignition
                                            pulse pick up is required. i believe in essence a 100 dollar eva could be
                                            built to experiment.

                                            if i were limited to only looking at one characteric the most info can be
                                            derived with a transducer monted to the engine to get precise frequency
                                            measurements to back calculate what component is causing the resonance.
                                            further the second most important thing is being able to quantify the
                                            magnitude of the imulse so you can identify which resonance is THE one that
                                            you are looking for .

                                            last is rotational tracking this is the least useful and the first
                                            recommended as all other parameters can be calculated using the above two
                                            methods, however being that crankshaft pulse is readily available to
                                            backprobe at the ecm connector it would be very handy to compare these
                                            three in a dso type arduino box and graph them in synchrony to paint the
                                            whole picture and make the resonance readily identifiable.


                                            What I really want to know is what exactly is the O.P. trying to do ie why
                                            are we measuring resonances and comparing them to other vehicles?

                                            As an auto tech i have never fixed a vehicle in my life :)

                                            What i do is resolve concerns and i find this concern to not currently be
                                            defined enough to resolve :)

                                            ( oh p.s rate of resolved conerns 97 percent in 7 yrs withh chrysler :)


                                            --
                                            jeremy youngs


                                            [Non-text portions of this message have been removed]
                                          • jeremy youngs
                                            DOH !!!! :)) simple cheap effective had to remeber bak to the first nvh class here this is the down and dirty old school tool !!! ( maybe a little ot as its
                                            Message 21 of 23 , Mar 3, 2013
                                              DOH !!!! :))

                                              simple cheap effective had to remeber bak to the first nvh class here
                                              this is the down and dirty old school tool !!!
                                              ( maybe a little ot as its not electronic !!)
                                              http://www.treysit.com/16.html


                                              did i just answer my own post doh enjoy

                                              --
                                              jeremy youngs
                                            • A6intruder@myo-p.com
                                              I am the OP and I have tried to be completely forward as to my goal, I stated this earlier: I am trying to figure out the basic
                                              Message 22 of 23 , Mar 4, 2013
                                                I am the OP and I have tried to be completely forward as to my goal, I
                                                stated this earlier:

                                                "I am trying to figure out the basic sensor/processing/display/record
                                                process now on my car so that later I can use it to analyze another
                                                combination of engine/gearbox/load."

                                                The point is to be able to test a given combination of engine/gearbox/load
                                                for destructive resonant frequencies in the full range of operation, engine
                                                RPM varying from idle (700 RPM) to max RPM (5500 RPM). I figured my turbo
                                                charged V-8 Mustang would be a good development test bed since I can load
                                                the engine very heavily to see "normal" power pulses with this process
                                                which aren't resonant in this parts combination. If there were a
                                                destructive resonant frequency in the operational range it would surface as
                                                a much larger magnitude than the regular power pulses from the engine, at
                                                whatever frequency it exists.

                                                So if we can see the "standard" power pulses with this process on my car
                                                then when I bolt a similar engine to different gearbox and load (say a
                                                propeller) on a test stand then I can monitor to see if the new combination
                                                has an resonant frequency within the normal range of operation.

                                                I really doubt my car has a resonant frequency in its range of operation as
                                                I have flogged that car on the street and at the drag strip throughout the
                                                full range of operation and it hasn't self-destructed.

                                                Everyone has been very helpful on this discussion, thank you. I have no
                                                doubt the information I am seeking can be determined from the gear teeth
                                                sensor, it is just a matter of processing that data stream. Jan has pointed
                                                out some of the numerical limitations to that process.

                                                Thanks,

                                                Dan

                                                -----Original Message-----
                                                From: Electronics_101@yahoogroups.com
                                                [mailto:Electronics_101@yahoogroups.com] On Behalf Of jeremy youngs
                                                Sent: Monday, March 04, 2013 12:19 AM
                                                To: Electronics_101@yahoogroups.com
                                                Subject: Re: [Electronics_101] Re: How to analyze change in frequency?

                                                I believe he said the resonance he is looking for would be at 1/4 the
                                                rotational frequency.

                                                Why not measure the period between gear teeth, and compare how it changes?
                                                It seems to me that what you are looking for is FM impressed on the pulses
                                                from the gear teeth.

                                                Steve Greenfield AE7HD

                                                steve i believe accel decel curve could be extrapolated via demodulation as
                                                you suggest. however this would assume abunch of ommitted truths that need
                                                reconciliation. just a few i wil miss them as i dont wish to write a thesis
                                                here :)

                                                1 this meaure is taken at the flywheel

                                                2 what exactly are we looking for ? just the 8 impulses in 2 revolutions?

                                                ( the op hasnt been as forward on what he is looking to do here as would be
                                                required)

                                                3 there will be MANY resonances as anything attached to the crankshaft will
                                                have a natural resonant frequency

                                                4 there will be 1st and second order harmonics dominating this analysis

                                                some means of isolating the suspect resonance is needed ( also to note what
                                                IS the suspect resonance? this has not been defined !!!!)

                                                (without definition i cannot help lead to a resolution :)

                                                5 what are the particulars of the test method i e under load ? going down
                                                the road? idling in the driveway? these conditions will radically affect the
                                                identifying of suspect parameters and will lead to different results

                                                in short i think an arduino with accelerometer, transducer and ignition
                                                pulse pick up is required. i believe in essence a 100 dollar eva could be
                                                built to experiment.

                                                if i were limited to only looking at one characteric the most info can be
                                                derived with a transducer monted to the engine to get precise frequency
                                                measurements to back calculate what component is causing the resonance.
                                                further the second most important thing is being able to quantify the
                                                magnitude of the imulse so you can identify which resonance is THE one that
                                                you are looking for .

                                                last is rotational tracking this is the least useful and the first
                                                recommended as all other parameters can be calculated using the above two
                                                methods, however being that crankshaft pulse is readily available to
                                                backprobe at the ecm connector it would be very handy to compare these three
                                                in a dso type arduino box and graph them in synchrony to paint the whole
                                                picture and make the resonance readily identifiable.


                                                What I really want to know is what exactly is the O.P. trying to do ie why
                                                are we measuring resonances and comparing them to other vehicles?

                                                As an auto tech i have never fixed a vehicle in my life :)

                                                What i do is resolve concerns and i find this concern to not currently be
                                                defined enough to resolve :)

                                                ( oh p.s rate of resolved conerns 97 percent in 7 yrs withh chrysler :)


                                                --
                                                jeremy youngs


                                                [Non-text portions of this message have been removed]



                                                ------------------------------------

                                                Please trim excess when replyingYahoo! Groups Links
                                              • Howard Hansen
                                                Hello Dan, A popular Frequency to Voltage Converter IC is the LM2907-N/LM2917-N IC. See: A recommended
                                                Message 23 of 23 , Mar 6, 2013
                                                  Hello Dan,

                                                  A popular Frequency to Voltage Converter IC is the LM2907-N/LM2917-N
                                                  IC. See: <http://www.ti.com/lit/ds/snas555b/snas555b.pdf>
                                                  A recommended application circuit is Figure 16 on page 14. To be able
                                                  to detect variations in frequency you need a frequency to voltage
                                                  converter with a low output ripple. Hence this is why I recommended a
                                                  frequency to voltage converter with 2 pole Butterworth Filter to reduce
                                                  ripple.

                                                  To select component values for the Butterworth Filter one needs to know
                                                  the range of possible resonant frequencies. What is the range of
                                                  possible resonant frequencies? My guess is 43 to 367 Hz. This guess
                                                  comes from an engine RPM range of 650 to 5500 and 4 power pulses per
                                                  revolution.

                                                  The other Howard


                                                  On 3/2/2013 9:49 AM, A6intruder@... wrote:
                                                  >
                                                  > OK,
                                                  >
                                                  > Just answering Jan and Jeremy got me thinking.
                                                  >
                                                  > Without looking at any data sheets let's say we have an IC that converts
                                                  > frequency to voltage. The Hall effect sensor puts out a square wave signal
                                                  > with equal high and low durations. So each time the sensor waveform
                                                  > crosses
                                                  > a certain voltage (say 2 volts) it allows the IC to determine
                                                  > frequency and
                                                  > output the corresponding signal voltage.
                                                  >
                                                  > With a completely smooth turning gear wheel at a steady RPM we will get a
                                                  > very steady signal voltage. Any time the frequency starts to vary the
                                                  > signal voltage will go up or down. In the case of four power pulses per
                                                  > revolution the IC should see four areas of changing voltage in each
                                                  > rotation
                                                  > of the gear wheel. If you hooked an oscilloscope to the output of this IC
                                                  > you would see a steady horizontal line for a steady RPM with no power
                                                  > pulses. With power pulses you would start to see those four areas of
                                                  > changing voltage.
                                                  >
                                                  > The peak amplitude of the changing voltages would signify the magnitude of
                                                  > the resonance. Large resonance would be a faster change in frequency since
                                                  > the mechanical amplitude of the disturbance has to happen in the same
                                                  > amount
                                                  > of time...
                                                  >
                                                  > I'm thinking out loud here. I need to dig into some data sheets and
                                                  > see how
                                                  > fast these IC's really are...
                                                  >
                                                  > Thanks,
                                                  >
                                                  > Dan
                                                  >
                                                  > -----Original Message-----
                                                  > From: Electronics_101@yahoogroups.com
                                                  > <mailto:Electronics_101%40yahoogroups.com>
                                                  > [mailto:Electronics_101@yahoogroups.com
                                                  > <mailto:Electronics_101%40yahoogroups.com>] On Behalf Of Jan Kok
                                                  > Sent: Saturday, March 02, 2013 12:09 AM
                                                  > To: Electronics_101@yahoogroups.com
                                                  > <mailto:Electronics_101%40yahoogroups.com>
                                                  > Subject: Re: [Electronics_101] How to analyze change in frequency?
                                                  >
                                                  > A couple of questions: How many teeth are there on the gear that the
                                                  > sensor
                                                  > senses? And, is there some way to tell where the "0" position of the
                                                  > flywheel is?
                                                  >
                                                  > I would suggest buying or borrowing a digital storage oscilloscope with a
                                                  > large memory (say 1 million samples or so) that can store waveform
                                                  > data to a
                                                  > USB key.
                                                  >
                                                  > Capture a bunch of waveforms from the sensor, and analyze them at your
                                                  > leisure on your computer.
                                                  >
                                                  > You'll get a frequency modulated square wave from the sensor. The
                                                  > higher the
                                                  > RPMs, the higher the frequency and the shorter the period of the square
                                                  > wave.
                                                  >
                                                  > Write a program to measure the period of each pulse, and plot the
                                                  > frequencies of the pulses (inverse of periods). You can use the Excel
                                                  > graph
                                                  > wizard to plot your data.
                                                  >
                                                  > Does the graph of the frequencies look somewhat sinusoidal? That graph
                                                  > would
                                                  > show the frequency modulation of the sensor square wave, and the cycles in
                                                  > the sinusoid should correlate with the power strokes of the pistons. The
                                                  > sinusoid should have much larger amplitude when the engine is under load.
                                                  >
                                                  > The amplitude should also be larger at certain RPMs where there is
                                                  > rotational resonance, compared with RPMs where there is no resonance.
                                                  > However, my hunch is that it will be hard to see any resonance, for
                                                  > several
                                                  > reasons: the resonant frequency may be higher than the sensor squarewave
                                                  > frequency, friction in the engine and drivetrain will act to dampen any
                                                  > resonance, and the resonance may be buried in random noise.
                                                  >
                                                  > Sounds like a fun project. I'll be curious to hear how it turns out.
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                                                  > Please trim excess when replyingYahoo! Groups Links
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