Inductive tachometer Tiny Tach, Sendec

Discussion in 'OnBoard Electronics & Controls' started by dskira, Jun 23, 2013.

  1. dskira

    dskira Previous Member

    Is members have some experience with the inductive tachometer like the Tiny Tach or the Sendec with the wire going around the cable spark plug?
     
  2. hoytedow
    Joined: Sep 2009
    Posts: 5,522
    Likes: 221, Points: 73, Legacy Rep: 2489
    Location: North of Cuba

    hoytedow Wood Butcher

    Someone on another forum made mention of a non-contact laser tachometer, but they only work when the cowling is removed. I have no such experience but am also considering buying a tachometer.
     
  3. dskira

    dskira Previous Member

    Hoyt, I read the Sendec is only one wire going around the spark plug, the Tiny Tach as an other wire going to the engine ground.
    I wounder how they work.
     
  4. hoytedow
    Joined: Sep 2009
    Posts: 5,522
    Likes: 221, Points: 73, Legacy Rep: 2489
    Location: North of Cuba

    hoytedow Wood Butcher

    I am interested to learn also.
     
  5. Richard Woods
    Joined: Jun 2006
    Posts: 2,203
    Likes: 159, Points: 63, Legacy Rep: 1244
    Location: Back full time in the UK

    Richard Woods Woods Designs

    I have had two of them. One worked well on a Yamaha 4 stroke, but with my Tohatsu I can set it to under read (8 pulses) or over read (6 pulses) I cannot set it to 7 which is what is needed. Sorry I don't understand engines, so may have it back to front. But they do work. Also the hour meter is useful

    Very cheap on ebay (USD10 or so), but I think those are Chinese copies

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  6. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 146, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    Such tachometer designs emerged for the first time some 50 years ago. Because there is an extra amplifier stage needed for the weak signal, they are susceptible to electrical "noise", making the wiring critical. A long wire length may require a shielded cable.

    Using the ignition coil or the stop switch as a signal source is much easier and reliable.
     
  7. hoytedow
    Joined: Sep 2009
    Posts: 5,522
    Likes: 221, Points: 73, Legacy Rep: 2489
    Location: North of Cuba

    hoytedow Wood Butcher

    Would regular coaxial cable(like for TV) work?
     
  8. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 146, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    Certainly Hoyt.
     
  9. hoytedow
    Joined: Sep 2009
    Posts: 5,522
    Likes: 221, Points: 73, Legacy Rep: 2489
    Location: North of Cuba

    hoytedow Wood Butcher

    Thanks.
     
  10. dskira

    dskira Previous Member

    For this connection it will be for a classic electronic tachometer or still a inductive tachometer?
     

  11. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 146, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    Classic tachometer circuits have a relatively low impedance (5-20 K-Ohms) with a protection circuit to suppress the 200+ flyback voltage from the coil.
    The inductive ones have a much higher impedance because otherwise the signal collapses. I have also seen tachometers with a number of dip switches at the back to select 2/4 stroke, number of cylinders AND the input source.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.