Building a non-contact tach ~100k rpm

Discussion in 'The Projects Forum' started by aaron87, Feb 10, 2011.

  1. aaron87

    Thread Starter New Member

    Feb 10, 2011
    1
    0
    Hey guys,

    I am currently working on my senior design project and we need a tachometer to measure the compressor speed. We are building a jet engine and would like to have an integrated component instead of an off-the-shelf. The engine would see 100k RPM max.

    Ideally, we would like to have both a readout screen so see real time as well as a voltage output to a data acquisition card. I am a mechanical engineer so I have limitied knowledge about how to design circuits, but I can build them.

    I'm sure a tutorial exists out there, but I cannot to seem track one down

    Thanks
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,031
    At that speed you could use either IR or hall effect. The IR approach would bounce a beam off a reflective spot somewhere on the spinning machinery. The hall effect approach would require a small moving magnet. Balance is obviously an issue at that rpm, so the choice is not trivial. I think, could be wrong, that the IR components might be less rugged. What environmental parameters are you dealing with? Heat, vibration?

    Once you have a pulse, there are all sorts of ways to get rpm. You could make a frequency-to-voltage circuit and read voltage with a cheap DMM. You could make a divider and divide your pulses down so that you could use a cheap digital tachometer or speedometer. More fancy DMMs can measure frequency. Then there are data acquisition devices (I have a LabJack, ~$115) that could easily handle this.
     
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