Tesla's "COIL FOR ELECTRO-MAGNETS".

[MileHigh]

Conrad:

Okay, let's assume that a vertical orientation on your monitor for purposes of this posting is equivalent to magnetic north-south.  Up is north and down is south.  Left is west and right is east.

I will simply use "(C)" for the compass.

I am going to use arbitrary simplified vales for the variables to illustrate the example.  The actual values for the variables (current level, distance between coil under test and the compass, the angles of deflection of the compass) will be up to you.

We are going state the following:

1.  It is very important to align the test setup along the magnetic north-south of the Earth.
2.  Zero amperes through the coil will deflect the compass by zero degrees from magnetic north.
3.  One ampere through the coil will deflect the compass by roughly 80 degrees from magnetic north.
4.  The distance between the pancake coil and the compass will be 30 cm.
5.  The fist thing you do is find a convenient table to put the compass on where it is magnetically undisturbed and points towards magnetic north.  You want to keep the compass away from other potential sources of magnetic field.
6.  Optionally, you can place the compass on a small block of wood or something similar so the compass is at the same height as the axis of your pancake coil.

Here is the top-view of the test configuration.   

-----------------------------------------------------------
                                                    North
                 []
                 []
                 []  <----- 30 cm ------>  (C)
                 []
                 []
                                                    South
-----------------------------------------------------------

The test:

When you put the same current through each coil for the same setup you should see the same amount of compass deflection for the two coils.   If you try a few different current levels and a few different distances/geometries and get the same results then you will have definitively proven that the two coil configurations generate the same strength of magnetic field.

Understanding the compass deflection:

The compass will be aligned with the ambient magnetic field.   The two sources for the ambient magnetic field are the Earth (north-south) and the coil under test (east-west).   Magnetic fields add like vectors so the compass will simply be showing you the vector addition between the two sources of magnetic field.

The addition of the two magnetic field vectors produces a diagonal field vector so the compass will be at some diagonal offset from magnetic north.  If you have graticule markings on the compass you will be able to make very accurate readings of the compass deflection.

Note that it would take "infinite current" flowing trough the coil to make the compass needle deflect by 90 degrees because of the vector addition.   That's why I arbitrarily stated that the compass would deflect by "80 degrees for one ampere of current flow."

The closer the deflection of the compass needle to 90 degrees the more "coarse" the measurement is because you are losing your "differential measurement sensitivity" and hence there is less information there.  I would suggest that you keep your compass deflection measurements between zero and 80 degrees or less.

There is nothing stopping you from putting high current through the coils for a perhaps 10 seconds so the compass reading can stabilize.  Naturally you can decide how far the distance will be between the coil under test and the compass and that will allow you to use lower current levels if you want to.

If you do choose to do the test have fun!

MileHigh

[MileHigh]

Conrad:

I can see that you already did a basic test.  I just tried to formalize the test in my long description to make it (hopefully) clear for anyone that wants to make some relative magnetic field strength tests between two or more coils.

MileHigh

P.S.:  You have a beautiful compass!

[conradelektro]

@MileHigh:

Thank for outlining a test in such a precise way. I will do this test tomorrow in exactly the way you designed.

You will see my post about a magnetic field test I did just now. I hope it was executed in the right way. (I am tired right now and have not yet carefully studied your test proposal, but I will tomorrow.)

And I will make a video about the magnetic field test. This will help all interested forum members to see what I did. Hopefully I will get many suggestions and constructive criticism.

MileHigh has now become the official educator of the OU forum. All his predictions came true and all his suggestions and improvements worked like a charm. I personally made a great leap forward in my understanding of basic concepts.

Good night, Conrad

[synchro1]

I'm ready to clean both you clowns out on a gram of iron filings per joule of capacitor discharge magnetic attraction comparison between the two coils. I'm willing to bet any amount of money that I get a higher weight to power ratio with the Tesla series bifilar pancake. Come on now and try and pretend the coil has no magic! All those test results are completely inane and have nothing whatsoever to do with the coils true purpose as an "Impulse Magnetizer".

[Magluvin]

I'm ready to clean both you clowns out on a gram of iron filings per joule of capacitor discharge magnetic attraction comparison between the two coils. I'm willing to bet any amount of money that I get a higher weight to power ratio with the Tesla series bifilar pancake. Come on now and try and pretend the coil has no magic! All those test results are completely inane and have nothing whatsoever to do with the coils true purpose as an "Impulse Magnetizer".

Your right. Just applying dc, especially low voltage, if your not looking for it, you wont see it.

45pf, you better be looking for very high freq initial spike at the time of applying the dc, not just looking at the DC magnetic field after the spike.

Oh well. Cheap tests. Cheap results. Testing pancakes such as shown, the motor better be running somewhere below FM radio freq of rotation. Doing low freq or dc tests on a coil that is designed for radio freq doesnt make any sense to me.  And then to say the results are conclusive when it comes to the difference between bifi and normal coils is only half baked.

Just made a second bobbin to match a coil I have(normal 1 strand, 42awg, 5kohm, 1.6h 2 1/4 dia, 1/8 in thick) to make an equal bifi for comparison.  The normal coil lights an led with a slow pass of a mag.

Will be using a primary pulse coil of 2 turns on the outer diameter for testing.


Mags