Help with Carl's fluxgate Gradiometer ckt.

[Malapais]

Calibrating the Fluxgate Gradiometer

Hello Carl,

I finally got my detectors alligned. They are not perfect but there is very little variation. I can get it perfect with the set screws loose, but when I lock them down I always get a small amount of movement somewhere that I cannot seem to overcome. Maybe from pressure on the walls of the detector? Anyway I have it locked down with only a very small sign of misallignment.

I am having trouble understanding the calibration technique now.

In the literature provided with the kit from Fat Quarters, I have two different sets of calibration instructions. One of them says that with the instrument 60 degrees from horizontal with the high end pointing North, (doesn't say wich end to hold high, the adjustable detector end or the fixed detector end) rotate the gradiometer through 180 degrees, and the other says to "rotate the tube (head over heels) through 360 degrees".

Is it supposed to be rotated 180 or 360 degrees? (does it mater which end is 60 degrees higher?) and when rotating, is it turned like a driveshaft in a car turns, or like a baton twirler spins a baton, or like a helecopter blade spins? The "head over heels" clairfier confuses me more than it helps since the HEAD and the HEELS parts of the instrument have not been defined.

Jim Hatt

[Carl-NC]

I flip it like a baton, with an E-W axis of rotation. Basically, during the chip's power-on calibration (first several seconds, I believe), you want to make sure it reads a maximum and a minimum field differential. So just rotate it all around, not too fast.

- Carl

[Malapais]

Calibration

Thanks Carl,

I hate to be a pain, but written instructions without drawings can be difficult to understand. A new word has entered the conversation, now we are "flipping" it like a baton E/W. My examples were, Baton, (for vertical rotation, I guess I should have used a windmill Blade for this one) & Helicopter blade (for horizontal rotation) & drive shaft (for spinning the tube).

Vertical rotation (like a baton) will not produce E/W movement, so I am assuming you misunderstood my examples and I am to move it (maintaining one end high and one end low by 60 degrees) like a helicopter blade rotates (Horizontally). One drawing would sure be worth 1000 words here.

I am trying to do this correctly to get the best calibration possible and the most accurate operation of the instrument. If I am just going to move it all around to catch all the different intensities of the field during calibration, why did I go to all the trouble of determining the point of 60 degrees from horizontal?

Before you ask Carl, YES, I am a Physicist, and like most Physicists, I do have a tendency for taking a very simple task and making it as difficult as possible.

My sincere appologies, and I am thankfull for your patience.

Jim Hatt

[Carl-NC]

OK, let's try a new simile... stand facing east (or west)... hold the mag in front of you, rotate it like you're an airplane and it's a propeller. The growling noise from the mag completes the effect.

I think the 60-degree thing is for the tilt of the Earth's magnetic, and may give a slightly better null, but I usually just do 360-degree rotations.

[Bytarantuna]

My gradiometer kit Problem

Hi carl, I'm getting from Fat Quarters doing gradiometer set. and it is not no sound but the speakers in an LCD to connect I do not know what kind. My voltage 3.8V - 4.8V comes between. What is a sound reason not to come? Which model can I connect and LCD?