New Polymer Neodium magnet VIDEO, standard pickup constructions tests and comparison

[RedHouse]

Totally agree.

I've asked David(S) a million times if we could make a "Buy-n-Sell" subforum and move all this freek'n crap there. Spamming and shilling by Elepro, and MrCandy is not what this forum is supposed to be about.

Specially the sticky at the top for the CNC Winder (which never went anywhere), and we need the mods to proactively move stuff to appropriate subforums.

[David Schwab]

Totally agree.

I've asked David(S) a million times if we could make a "Buy-n-Sell" subforum and move all this freekin crap there. Specially the sticky at the top for the CNC Winder (which never went anywhere). And we need the mods to proactively move stuff to appropriate subforums.

I have no control over that. You need to ask tboy. Basically all I can do is edit/delete/move posts in the Pickup Makers section.

But still, any arguing I see is from people with options about the subject. Not everyone in the forum is going to make pickups just for themselves. Some make them for profit. That has nothing to do with arguing.

MrCandy started this thread to show some magnets that he makes for sale. OK, that's sort of an advertisement, but people will buy them or not. He did the same thing with the magnet wire. I got some samples of both and made objective comments on the products.

So we came to this end of the discussion because I found some issues with the listed specs of the magnets. Any arguing between parties is just a personality thing. But he felt my gauss meter was at fault, and I'm quite sure it isn't. You backed me up on that.

I put the CNC sticky there because people were always talking about making winders. I had hoped the group buy thing would have happened, but regardless it's a good resource. If you made something available we could use I'd make that a sticky too, just as the pickup makers FAQ is a sticky.

[big_teee]

Lot's of us sell things, and a little notation in the signature is fine.
Some of these guys never get on here unless they are Plugging something.
Like someone getting on LetterMan when they have a new book to sell.
I thought the wire for sell was Cheezy also, but that's Strictly IMO.
I'm sure Tboy would Love to sell them Advertising.
Getting on here talking about ideas on how to make something, even when we know it's for sale is one thing.
At least with that, we all benefit from the ideas.
Getting on here to force feed us something is another.
I also think listing your PayPal Info in your signature is very tacky.
Instead list your own website, then if you choose you can I'm sure do PayPal from there.
That is what Our Moderator does, and I admire him for it.
End of Rant!
B_T

[RedHouse]

I don't think T-Boy would object, he'd got the "Parking Lot/Flea Market" subforum in the root of the forum.

It would be nice if the main section of this Pickup Winders forum wasn't a personal-shilling platform for a handful of individuals.

[Steve Conner]

Mr Candy's formula seemed quite reasonable to me. The sensitivity doesn't appear because he is recalculating it as the slope of the sensor's transfer characteristic. If sensitivity = dV/dB then (Vmax-Vout)/(Bmax-0) is a straight line approximation to dV/dB and should come out the same as the datasheet figure, since the maker claims his sensor to be linear after all.

I don't really expect gauss measurements to be repeatable. It is just a hunch, I'm not sure why. One thought I had is that the field lines could be quite non-uniform near the surface of the magnet. Enough so that the gauss reading you get depends on the thickness of the Hall sensor package, and how far it holds the sensing chip away from the magnet surface. That thickness isn't specified anywhere in the sensor datasheet, so it could vary quite a lot. (This is Murphy's law of electronic design: Anything that isn't specified in the datasheet will turn out worse than you could possibly imagine.)

Maybe one of our heavyweight resident physicists can comment.

[David Schwab]

I hold the sensing side of the sensor right against the magnet or pole I'm reading. In the case of enclosed pickups, I touch the cover with it. It does vary as you move around the magnet. When I have a magnet like that I set the sensor for peak hold, or I just average out the readings.

The thing is that these units, like a Gauss or Tesla are known values. They aren't vague. So if your meter is calibrated it should give you the actual value. The fact that I have other magnets that I'm quite sure are higher than 600G, and measure what I would expect from that type of magnet, and that the NiB magnets being tested read more than 600G tells me that the original specs seem off.

Also based on the fact that Brad had used the services of Jason and Wolfe to check the meter against their commercial units also leads me to believe that I'm getting accurate readings.

[Steve Conner]

Sure. My point is that a non-uniform field doesn't have a single "gauss". If you calibrate a bunch of gaussmeters to read the same with a uniform field, then take them to a non-uniform field, even if you try them all in the same spot they might all read different depending on the detailed structure of the field.

And likewise if you calibrated them all at the same spot in a non-uniform field, and then took them to another field that was non-uniform in a different way.

I think this is what's going on here. MrCandy charges his magnets so they read say 50mT on a sensor calibrated at the factory for a uniform field. They ship with a MrCandy shaped field that is 50mT in the spot where the Honeywell sensor chip happened to end up.

You guys then test them with meters calibrated for a typical pickup magnet shaped field, in a different spot.

[RedHouse]

...I don't really expect gauss measurements to be repeatable. It is just a hunch...

Well I'm not one of the heavyweight resident physicists here Steve, but I know the meters and they can test magnets with repeatability, you only have to test the same spot on the magnet, same orientation, same sensor.
(don't move/wiggle at all)

On my bench test jig I made a framed platform out of FR4 scraps that acts as an alignment/holder, the sensors (yes, plural) are embedded into cutouts in the FR4 and any magnet can be dropped in and tested, removed/replaced and tested again repeatably.

The bar magnets I used in the cal scenario were marked (Wolfe's idea) and tested at the same spot each time, but never mind. It's going to be one of those argy-bargy things around here.

Lauders this year?

[Steve Conner]

OK, maybe I chose my words badly. I meant that I don't expect gauss measurements made by one lab to be reproducible by another. For the reasons that you point out, the reading you get depends so crucially on the position and orientation of the sensor. That is to say the Hall chip itself, not the plastic package, which might be thicker on the Honeywell part than it is on the Allegro.

Yes, if you are in Glasgow again it would be a pleasure, does this forum have a beer smiley?

[-Elepro-]

Mr Candy's formula seemed quite reasonable to me. The sensitivity doesn't appear because he is recalculating it ....

yes Steve, i understand the intention of that formula... and with his values the recalculate sensitivity is 3.0 mV/gauss .... very different from datasheet....

Why?

because he does that without a known magnet of 840 gauss but taking this value from datasheet .... and he saturated the sensor with a big magnet.... then in the non-linearity zone of sensor...

then formula works in other hands.... here is just a fantasy-formula/method....

about gauss pickup measurements i totally agree with non easy repeatability.... i never gave too much importance to calibration.... gaussmeter is just for a indicative value in pickup making....

bye

[Steve Conner]

So, if we take this error in the sensitivity into account, is it the right amount and direction to explain the differences in the gauss readings? Or does it just make things worse? I'm posting this from an ipod and can't see the Honeywell datasheet without zorching my post.

I'm not suggesting that the Elepro gaussmeter is bad somehow, there is plenty of room for mistakes even with the electronics working perfectly.

[David Schwab]

OK, maybe I chose my words badly. I meant that I don't expect gauss measurements made by one lab to be reproducible by another. For the reasons that you point out, the reading you get depends so crucially on the position and orientation of the sensor. That is to say the Hall chip itself, not the plastic package, which might be thicker on the Honeywell part than it is on the Allegro.

Yes, if you are in Glasgow again it would be a pleasure, does this forum have a beer smiley?

Right, but you can get certified calibrated gauss meters. So there must be reference sources available.

Also, the variations in a magnet are not as large as the difference I measured. The magnet listed at 65mT (650G), read 1193G (119.3mT) at it strongest part. The weakest point was no where near 650G. It might have been 1060 or something.

And since a full size A5 reads about 650G, a NiB reading 650 G would be REALLY weak. Even very tiny neo magnets I have around here are much stronger than that. And if my meter was that far off, than the 650G alnico I have would be about 300G? I don't think so.

Beer is good! Plus for what ever reason I've always wanted to visit Scotland. It must be the accent the women have.

[David Schwab]

gaussmeter is just for a indicative value in pickup making....

Exactly.

[RedHouse]

Beer is good! Plus for what ever reason I've always wanted to visit Scotland. It must be the accent the women have.

Definately, and as B. Franklin once said "Beer is proof that God loves us"

I agree, the Scottish women sound nice, I love their accent.
(that's partially why I married one)

...Yes, if you are in Glasgow again it would be a pleasure, does this forum have a beer smiley?

I'll be there. PM me your cell and email, we'll have a wee swally. Dang I love those Fish-n-chips at Lauders Pub, great grub!

[RedHouse]

...about gauss pickup measurements i totally agree with non easy repeatability.... i never gave too much importance to calibration.... gaussmeter is just for a indicative value in pickup making...

You should put that remark in your gauss meter group buy thread, might influence potential customers.

Of course it's an indicactive tool, but using it in production is a great QA step, both on outgoing product and incomming stock, all the rest (of the argument) is worthless drivel.