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
    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

  2. wayneh


    Sep 9, 2010
    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.