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Sometimes you need to know which side of a magnet is the north pole and which is the south pole, for instance if you’re using it with a sensor that’s only sensitive to one pole or the other.  Emovendo’s Magnetic Pole Searcher/Finder will quickly indicate which pole is which.

The tool consists of an alnico bar magnet mounted on gimbals so it can move freely in all directions. You simply move the probe toward the magnet, and the green tip points to the north pole and the red tip points to the south pole.

You’ll pay $9 for Emovendo’s Pole Finder, plus $8 shipping.

Magnetic Pole Finder [Emovendo]


13 Responses to Tell North From South

  1. Mr.Miz says:

    Ok so help me out here. You need to know the poles when your doing what? I know I’m a little dense, but I thought magnets where “this side sticks to metal, and this side doesn’t”
    Help a slow guy out.

  2. @Mr.Miz:

    No problem, Unipolar Hall-Effect sensors (A fancy name for a common type of magnetic switch) only activate with the south pole of a magnet; if you install the magnet backwards it won’t work.

    You’ll see these kind of sensors used in anti-lock brake systems, brush-less motors, and other position and motion sensing applications.

    Yes, this is a rather specialized tool, but I thought it was neat.

  3. Rusty says:

    All sides of a magnet stick to metal.

    Magnets are “polar” though with a north and south pole, like the earth. 2 magnets will not stick together N to N or S to S, only N to S

  4. Dustbuster says:

    Um, you have a sensor that only senses one pole of the magnet, you have the magnet. So you plug in the sensor and then you move the magnet close to it, the side of the magnet that makes the sensor work is the side you want. Am I missing something here?

  5. Davo says:

    Eight dollars shipping, for a nine dollar product?

  6. Darren Clark says:

    Actually it’s quite useful if you’re making a motor or generator (kids projects, small generator for wind mill, …). But for $17.00 I’ll make my own.

  7. snoopy says:

    I’ve always found these useful when I’m sorting my magnetic monopoles.


  8. heywood says:

    yeah, it’s really tough to buy a rectangular magnet and mark it with n & s poles…much easier to spend $17 frickin’ dollars on a single-useful-purpose doohickey.

    I have a priceless wad of gum that was in Brad Pitt’s mouth to sell ya too…only $500!

  9. David Bryan says:

    Ain’t it just a glorified compass?

  10. bob says:

    How does a guy at home, starting with a magnet, figure out which is which without one of these?

  11. Use a compass. A 50-cent eBay one will be adequate.

    The north end of the compass needle is the north magnetic pole of the tiny needle-magnet; it will point at a magnetic south pole.

    (And yes, this does mean that the Earth’s magnetic “north pole” is actually the SOUTH pole of the giant planet-magnet.)

    It’s possible that a strong magnet might remagnetise a cheap compass so it points in the wrong direction, if you bring it close to the compass. You can ID a magnet’s poles with a compass from a considerable distance, though.

    I think the gizmo this post is about is more of an educational device than a practical tool. But if you do have to ID magnet poles, and especially magnet FIELD SHAPE, while you’re up to your elbows in car parts or something, it’d be nice to have a larger, sturdier tool that doesn’t need to be held level.

  12. kyle says:

    If you google build a homemade wind turbine there are some where you have coils of wire in a resin disc and two discs with rare earth magnets in them. You have to alternate the poles in order to generate electricity. If you were building these frequently i could see the purpose of it. If I were to build one i would find a magnet designed to be used for educational purposes with the poles marked then just see what side it is atracted to and what side repels it, but it is an interesting idea.

  13. David says:

    Dustbuster, you might like putting a car completely together, having it not work, then having to take it back apart, all to save $17. But I don’t.

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