Hall Sensor with Range > 1000mT

Hall sensors are integrated with analog circuitry intended for sensitivity; could you use the old, crude bismuth resistor instead? It doesn't give sign of the field, isn't directional, but it doesn't saturate either.

Hi Klaus,

Maybe you could reduce increase the range by putting a piece of iron near the sensor to steal some of the field. You'd need to calibrate it with an unmodified sensor.

Can you tell us more about the magnetic circuit in which you want to measure this induction? I'm asking this because I'm thinking of some kind of inverse flux concentration. That would require the possibility to locally increase the area through which the flux passes. 25% increase then gives you a reading of 800 mT when the field in the rest of the circuit would be 1T. But I have absolutely no idea whether or not you are constrained in your design, or whether you have to do a measurement in an existing magnetic configuration.

joe

Also, beware hysteresis, and saturation (any permeability nonlinearity, really).

Does it help to simply use a regular sensor at an angle? Output goes as the cosine against field lines. Can't guarantee the Hall effect won't screw up more things inside the chip, though.

Tim

Have you tried the ones from floppy drive brushless motors? I have seen boards with three of them having their excitation pins connected in series, (with a current-limiting resistor), between the 5V and 0V power rails. Each sensor had its two output wires going to the input pins of a comparator in the motor driver chip. Bearing in mind the voltages applied, I doubt they have any amplifiers built in, so I expect they would have no problem with measuring fairly high fields. I built one into a probe for comparing magnets, but I don't have any calibrated fields (and I don't feel like winding Helmholz coils right now) so I can't test it for you at 1T.

For really extreme high fields, you could use a piece of PCB foil. For hobby use, maybe a large thin-film SMT resistor could be used too, if you scratch off the insulation and add silver paint in the right places.

Chris

A 1 T Helmholz coil, that would be something. :)

joe

I would discharge a capacitor into it. Yes, it would need to be mechanically sturdy! The only other way I can think of to calibrate a 1T hall effect device is with a more conventional approximately 1T magnet that can be measured accurately by spinning a small coil of known area and measuring the induced voltage to measure the field. All of these methods sound like a lot of work so someone else can do it!

Chris

Any idea where you can get a bismuth resistor?

To the OP, for a crazy idea, how about measuring the Hall effect in copper... right on the pcb. (You'll probably need a lot of current...)

It seems to me there should be some commercial unit out there.

George H.

Here are some high field ones... I'm guessing there are more out there.

George H.

Here's another,

Googleing "high field hall sensor"

George H.

The MLX90215LVA is the best choice from Melexis. Unfortunately you'll need a $1200 programmer to use it!

I consult for Melexis if you have any questions I'm happy to help.

On 22 Sep 2015 13:41:15 GMT, joe hey Gave us:

snip

You guys are lame for failing to declare values.

It is not 1T

It is 1THz.

Or 1 TH for Henrys.

Den tirsdag den 22. september 2015 kl. 17.14.40 UTC+2 skrev DecadentLinuxUserNumeroUno:

T as in Tesla

-Lasse

Why do you do this to yourself? Why???

T *is* the unit of magnetic field strength.

In the voice of cookie monster, "T is for Tesla, that's good enough for me."

George H. "Tesla, Tesla, Tesla starts with T"

Well, you don't write anything about your budget, but in my experience, the only useful Hall probes in the 1 T range are those from FW Bell and Projekt Elektronik

Klaus

Yes, I thought about that, but I am a little worried about non-linear effects

Regards

Klaus

It's for measuring the Flux inside a slot of a permanent magnet synchronous motor to evaluate the BEMF waveform during operation. We have added a coil on top of the standard coil, but the coupling between the standard coil is high so instead of monitoring the BEMF, we instead just measure more or le ss the applied voltage from the inverter drive

That's the reason for using a Hall sensor, that will measure only the magne tic field and won't care much about common mode noise either

Cheers

Klaus

Nice idea, that could be an option. Thanks