Magnet Myths and Misconceptions

[MarkE]

I think you are misinterpreting what you see in Case 2.  Look at the conventional picture of the field lines. As you slide the Hall sensor along the side of the magnet with the face parallel to the magnet's long axis, the sensor experiences changing directions of the flux and at the midpoint the flux is mostly _parallel_ to the plane of the sensor: That is, no flux or very little goes through the plane of the sensor at right angles to it, so the sensor reads minimum flux here. (In the case of my particular sensor, the voltage output will be the midpoint of the supply voltage or about 2.55 volts, meaning no flux through the sensor plane.) As you continue to slide along towards the pole, the flux begins to curl back towards the pole so more and more of it goes through the plane of the sensor. When you started, the "arrow" of the flux goes through the sensor in one direction. As you progress along, the flux becomes more and more parallel so less and less goes through the plane of the sensor. Past the midpoint the flux begins to curl back and so more and more goes through the plane of the sensor, with the "arrow" now in the opposite direction wrt the sensor. When you are on the pole itself, and have turned the corner and rotated the sensor so that the plane is now flat to the pole, you get the maximum flux reading.

Exactamundo!

What is the part number of your sensor? Is it a true linear ratiometric sensor like I am using, or is it a "switch" type? It would be nice to see the data sheet for your sensor. I've already provided the data sheet for my sensor in a previous post.

[MarkE]

I agree, it looks like that, but thats probably because my hasty video job on the upper flux, in reality its different, see this new short video:


https://www.youtube.com/watch?v=zShIcIsvBS4&feature=youtu.be


Regards Itsu

Yes, and these esults should not be surprising.  The competing effects on flux density parallel to the dipole axis are the changing orientation of the field and the spreading of the field.  At the center of the magnet the orientation is all perpendicular to the sensor face, but the field has spread out giving the dip between the "camel humps".

[allcanadian]

@TK
Here is an interesting graph. Hold the hall sensor stationary with the face pointing to the center of the magnet then rotate the magnet on its center from pole to pole. I'm not seeing loops here I'm seeing a spherical field. The N and S poles of the magnet are the top and bottom of what appears as a sine wave. If it were loops then when the sensor face was pointed at the side then the measure should be zero which it is not, only at the exact center is it zero.


TK you need Labview.


AC

[Pirate88179]

TK:

I just watched part 2.  I really like those sensors that you purchased.  Those make reed switches a thing of the past for the projects I want to build.

Bill

[MarkE]

TK:

I just watched part 2.  I really like those sensors that you purchased.  Those make reed switches a thing of the past for the projects I want to build.

Bill

Bill when you do:  Buy A1324's they have much higher sensitivity of 5mV/G.  You might be able to find their predecessors the A1321 around cheap.