Magnet Myths and Misconceptions

[minnie]

   Nowhere to my knowledge has anyone ever showed anything like a figure of eight.
   I'd be most grateful to know where to look.
                      John.

[verpies]

Force is the integral of pressure difference over an area.

...just like attraction force is related to magnetic flux density gradient.

[itsu]

Nicely done, and perfectly in agreement with the _standard picture_ of the magnetic field lines. If you could overlay the standard image of the field lines, you'd see that your sensor readings are perfectly in accord with the picture in both direction and magnitude.

The slight asymmetry you detect, where the "dip" is at minimum value not exactly in the center of the stack, is probably due to the slight asymmetry in the Hall sensor itself. If you rotate the sensor 180 degrees you will probably find that the minimum (or maximum) will follow the rotation and appear on the other side of the actual center of the magnet stack, proving that it is the Hall sensor and not the field that is "offcenter".  The image below is from the Data Sheet for the sensor I am using, and you can see that the sensor's response is slightly asymmetric wrt the direction of flux through the plane of the sensor. Since this is a characteristic of Hall sensors in general, it probably is true for yours as well.

What is the part number of your sensor, and can you provide a Data Sheet for us to look at?

TK, thanks, 

the used Hall sensor was mentioned here:   http://overunity.com/14974/magnet-myths-and-misconceptions/msg431679/#msg431679

Its a UGN3503UA (similar to yours) and the data sheet can be found here:  http://www.alldatasheet.com/datasheet-pdf/pdf/55099/ALLEGRO/UGN3503UA.html

So the noted offset could be due to this asymmetric response, great.


Regards itsu

[tinman]

Tinman where did you say qualify pressure as gage or differential?  It is up to you to say what you mean.  I can go out and buy pressure sensors that are any of the three:  differential, gage, or absolute.

Oh-sorry Mark-what would you suppose the gages would be telling you when they are gages that read psi both positive and negative pressures. What gauges would you normaly use when reading water pressure in a pipe?.
Or do I havevto spoon feed you?
Unbelievable

[MileHigh]

Oh-sorry Mark-what would you suppose the gages would be telling you when they are gages that read psi both positive and negative pressures. What gauges would you normaly use when reading water pressure in a pipe?.
Or do I havevto spoon feed you?
Unbelievable

I think you need to check the attitude there Tinman.  You know the drill:  Make your points and advance your argument without drama and without disrespecting others.  I am sure that you have learned a lot of stuff from Mark in the past year or so.

You are dead wrong in the way you think how magnetic fields work as is clearly illustrated sometimes by your choice of words.  Hopefully you will eventually come to this realization yourself.