Magnetic field sensor?

Sounds like feedback fluxgate turf. There are some for around $50, but a lot bigger than you suggest. You could make your own, if it's a quantity application, but it would probably take a good chunk of a square inch, and some engineering.

Hmm, Well I think you told me about the honeywell GMR sensors (HMC1001) they claim a resolution of 27 uG. Would that work? (This was from a vibrating gradiometer thread... I thought there was another more sensitive sensor mentioned but I couldn't find it.)

George H.

I always recommend the Honeywell sensors... since I designed the control chip ;-) ...Jim Thompson

Honeywell HMC1001 comes pretty close.

On a sunny day (Thu, 26 Sep 2013 09:43:41 -0500) it happened Vladimir Vassilevsky wrote in :

On the compass side there are fluxgates... Or this:

How are you eliminating the earth magnetic field influence?

On the very sensitve end are SQUIDs...

from memory in the range of volts per uG experts in GMR sensors:

NVE Corporation (800) GMR-7141 (800) 467-7141

Excellent, thanks. that was the product I was trying to remember. (I better print out a spec sheet and stick it on my wall.)

George H.

Resolution is OK, but unfortunately there is one big problem with HMC sensors. The parameters are varying after each set/reset pulse. This variation is far worse then resolution limit.

Vladimir Vassilevsky DSP and Mixed Signal Designs

Maybe hysterises? I sent an email off to the NVE company above, and that l ooks to be 'my issue' with their sensors. Maybe JL's suggestion of a flux gate would work. A colleague made a flux gate with two side by side induct ors with a coil wrapped around both. You have to put a bit of current thro ugh the commercial inductors to get them to saturate... it gets a bit hot. But you can wave it around and 'see' the Earth's field. Calibrating would be an issue... you need some clever way to match the inductors. There's a zero offset too, he did that by displacing one inductor along the ir common axis, and then moving the common coil postion... much more work t han an IC solution.

George H.

Try the website from Sensitec. There you should find the AFF755B. This one claims a resolution of 2nT.

Nice thanks... any idea of cost? Here's the data sheet,

Dang I hate magnetic units... why the bleep do they use both A/m and Tesla. (OK I guess I just multiply by mu_sub_zero and get ~1.3uT per A/m)

George H.

And I'm in the OTHER camp. Why the bleep do they use those pesky Oersted and Gauss units? Absolutely USELESS terms.

I work in A/m, nanoTeslas, picoTeslas, and a lot into the femtoTesla ranges and HATE dimensions that don't relate to MKS which allows easy bouncing between Electrical Signals, Noise, Power, LaGrangian etc etc...

I guess it's a little like thinking in terms of microns, not mils.

Oh I'm sorry, I like MKS. Why do they use A/m? I 'know' Tesla and/or Gauss. A/m's are for coil winders. The above is a field sensor. (I hope that doesn't sound too cranky)

George H.

I have bought the GF 705 and 708. They are 7.5 Euro in 20 pieces each. Maybe your target will work. I think they are in similar range.

Naw, was fun, you provided my 'vent for the day'

Anybody know why A/m doesn't have anybody's name applied to it yet? Took me a long time to go from webers per square meter to Teslas. And, I won't even talk about how long it took to go from cycles per second to Hertz.

B and H obey different boundary conditions, so if you've got magnetic materials running around, it makes a big difference.

Cheers

Phil Hobbs

Huh?! How do the dimensions affect the analyses? Well, as long as all the dimensions use the same terms.

Sure. I guess I'm just sensitive about Magnetic field units from grad school... where I was extremely confused by all the different units/ conversion factors etc. (At least Gauss and Oersted are the 'same'.)

And then is B or H the magnetic field? Wiki seems to be of at least two minds on the subject.

I was later corrupted by Feynman who uses MKS units but then defines 'his own' H field such that B and H have the same units. (I tend to like that best, but then I can't talk to anyone else about 'my' H field because it has units of Tesla.)

(sorry for the rant) George H.

Amps per metre and oersteds are the units of H (the magnetic field).

Teslas and gauss are the units of B (the magnetic induction).

The names are so obviously backwards that EEs who do antennas and just about everybody in physics say "the B field" and "the H field".

The sensors all sense the B field AFAIK. (B is what actually affects electrons and so on.)

B = mu H

whereas

D = epsilon E.

At a material boundary, tangential E and perpendicular D are continuous. For magnetics, it's tangential H and perpendicular B.

The B-H area is measured in gauss-oersted.

And field calculations are much easier in cgs Gaussian units. You just have to get over the statvolt problem--multiply by 300 and all is well. ;)

Cheers

Phil