Hall Effect Magnetic Flux Sensor in very Strong Magnetic Fields

maxim

Dear PFs

I am facing a problem with finding a good Hall-effect magnetic flux sensor which should be fixed in the top of a probe working in a very intense magnetic field.

The probe must be aligned to a certain degree with respect to the direction of the main field. The requested alignement accuracy should be on the order of 1/10 of degree (or less even better).

The magnetic field is very strong, of the order of 16.5 Tesla (16.5 x 10^4 Gauss).

I had thought to place the sensor in parallel geometry, with its plane oriented parallel to the magnetic flux lines. Thus I expect to detect a zero voltage when the sensor is perfectly aligned to the main field, and a not-zero voltage which depends strongly on the angle between the direction of the main field and the normal to the sensor surface.
Afterwards I will try to elaborate such voltages (V_H) to get a feedback for the correct alignement.



Here's the problem: which kind of sensor can I test?
I've drawn my attention to the Lakeshore Hall device HGT-3030, but it seems to be very difficult to find.

Any experience here?

Can you suggest some commercial models with a easy schematic diagram or application note?

Thanks for your enthusiastic responses!

max

jim hardy

might Metglas be of any use?

here's a hobbyist article..see page 2 0f 6.
http://www.tinaja.com/glib/muse104.pdf

and
http://www.metglas.com/faq/?faq_id=24

maxim

Thanks Jim.

I think I need a more sophisticated device, as Linear Hall Effect Sensor ICs with a low linearity error and a good magnetic sensitivity.

jim hardy

got it.

They're not here?
www.lakeshore.com
Lake Shore Cryotronics, Inc. (614) 891-2244 fax: (614) 818-1600
e-mail: info@lakeshore.com


http://lakeshore.com/products/Hall-M.../Ordering.aspx

sorry for being nosey - just i'm fascibated by magnetics. once built a fluxgate magnetometer.

maxim

HGT-3030 Transverse Hall generator costs $444...

Magnetic sensitivity . . . . . . . . . . 6.0 mV/kG to 10.0 mV/kG
Nominal control current . . . . . . . 100 mA
Maximum linearity error . . . . . . . ±0.30% rdg (-10 to 10 kG) ±1.25% rdg (-30 to 30 kG)
Zero field offset voltage . . . . . . . ±75 µV (max)
Operating temperature range . . . . -40 ºC to +100 ºC
Active area . . . . . . . . . . . . . . . . 1.02 mm diameter



Honestly, I was looking for an equivalent inexpensive device.

maxim

No more ideas? :(

jim hardy

What physical size must this apparatus be?

What is it about the field that you want to measure? Intensity, direction, variations?

I have only tinkered as a hobbyist with a fluxgate magnetometer measuring earth's field and i dont have experience with fields as strong as you cited, which sounds like it might be in a speaker voicecoil airgap or something. I also tinkered with some LVDT position sensors (12 feet tall) at work... another story ...

My magnetometer sensed from kitchen table automobiles passing in the street, refrigerator door opening, it had surprising sensitivity. But you are looking for precise measurement of direction? Will your apparatus affect the local field?

Jack M Janicke's Magnetic Measurements Handbook is best "poor man's" introduction to the subject that i ever saw.
Here's Honeywell's introductory appnote.
http://www51.honeywell.com/aero/comm...on-Sensors.pdf

Sorry - i just am not expert in that field, so shotgunned you with what i could find 'cause you asked for help and there didnt seem to be much.
I dont know your degree of familiarity so hope you aren't offended.


old jim

jim hardy

http://www.diodes.com/datasheets/ZMT32.pdf

maxim

Hi Jim,

as wrote at the beginning the magnetic field I need to handle is very strong, of the order of 16.5 Tesla (16.5 x 10^4 Gauss)!

Yes, my application is not trivial. I need to measure flux variations of a strong magnetic field over an area of c.a. 1mm² with high accuracy.

The sensor will be placed inside the magnetic field, where a probe for nuclear measurements must be aligned to the lines of force.


Nice, I will have a look.

Com'on, where is the problem?

Thank you for your help!

jim hardy

It sounds fascinating and i wish i had experience to offer you.

But i'd get distracted trying to invent a new sensor out of Flint glass and Faraday effect.


Best of luck to you, sir, and thanks for your kindness.

old jim

f95toli

My advice would be to just buy a proper sensor. The fact that you are working with a 16T magnet means that you are using reasonably sophisticated equipment (you are obiously not doing this in your basement at home), and $400 is not much money under these circumstances.
Also, remember you will -regardless of what you end up using- need some form of reasonbly accurate read-out electronics; and good sensor will probably easier to read out, meaning you won't need a a bunch of extra kit just to compensate for the fact that your sensor is e.g. giving you a very weak signal.

maxim

Hi f95toli

In these circumstances $400 is too much when you have to pay from your own pocket...
I guess the driving of such a sensor is not trivial, and I have no experience on that.


This I know; infact I was looking for a HGT-3030 Lakeshore sensor.
In the meantime I hoped to find here peple with some experience in projecting of interfaces for Hall sensor, just to avoid lost of time fighting the silliest problems.

Perhaps another thread would be most suitable?


Thanks anyway for your input!

maxim

jim hardy

Get that Janicke book.

I hope he's still living - we exchanged several emails on my magnetometer.
He is very knowledgeable practical and helpful.
old jim

maxim

Hi Jim,

I've found it on Amazon. I will (re)start from that.

Carl Pugh

How are you making a 165 kilogauss field?
This high a magnetic field requires extremely expensive equipment.

maxim

It is a commercial cryomagnet made with superconductive wires working at the liquid Helium temperature (4.2 K). This has not been bought by myself, rather by the lab that asked my expertise. There is no budget saved for the project "Hall-sensor".
That's why I am looking for an unexpensive solution: this should get out of my wallet.
Unfortunately for me it seems that only (expensive) Lakeshore sensors are on the horizon...

jim hardy

That Zetex Hall effect angle sensor is under $3 here
http://www.futureelectronics.com/en/...4294938328-631


they spec it to 50 ka/m typical range,

no maximum field is given

if you bent the leads down it'd make your 1/4 inch size.

http://www.diodes.com/datasheets/ZMT32.pdf

again i realize this may be clutter.


over and out

old jim