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Coil magnetic field measurement

Coil magnetic field measurement

Coil magnetic field measurement

(OP)
Hi, I would like to have some suggestions for solenoid valve magnetic field measurement.
Some specifications: sensor diameter must be smaller than 14mm but <6mm preferred.
Accuracy: min. 0,1 % (max. field about 100 mT)
Frequency max. 7 KHz
NMR sensors are too big, fluxgates haven't got the bandwidth and hall elements and GMR sensors cannot fulfill the accuracy criteria. SQUID and SERF do not even come in question.

Anyone has got any ideas?
Thank you!

RE: Coil magnetic field measurement

Here's a lead I just found. I didn't dig all the way down... ...I'll let you investigate further to see if they have anything suitable. Good luck.

Senis Transducer Brochure (pdf)

RE: Coil magnetic field measurement

Unless you rework the problem, you've presented an impossible situation. I would revisit the accuracy requirement, particularly w.r.t. to the Hall and GMR sensors and look to either loosening the accuracy requirement or doing a direct calibration of the sensor or both

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

RE: Coil magnetic field measurement

I wonder if the Watt Balance might provide some ideas.

RE: Coil magnetic field measurement

(OP)
Thanks for the answers!
@ VE1BLL: Senis seems ok, I am looking for a cheaper alternative. I found this: http://www.hoeben.com/productdata/Datasheet-HE144-...
As far as I see it, Watt Balance is for mass measurements.
@IRstuff: The problem really has high criteria, they might be lowered if there was no solution.

RE: Coil magnetic field measurement

The Watt Balance also involves extremely high precision calibration (or perhaps calculation) of solenoids and their magnetic fields. Perhaps there's some advice in the related literature; just in case you run into a road blocks.

RE: Coil magnetic field measurement

A Watt Balance approach potentially could be taken, but I've only seen that approach on radiometers, and even then, the absolute accuracy was only around 0.5%. Additionally, with a 0.1% measurement tolerance, you'd need submicron positioning accuracy, particularly the closer you get to the poles.

Your cited Hall effect device appears to net out at about 0.5%, when you account for all the parasitic effects, like temperature, Joule heating, nonlinearity, etc.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

RE: Coil magnetic field measurement

(OP)
It is important, that my coil is about 15 * diag=10mm, so watt balance should come out of question.

Which cited Hall Sensor are you referring to? Please note, that the temperature coefficient of the offset can be mostly compensated by the HE 144 Sensor.

RE: Coil magnetic field measurement

The 'Watt Balance' has been in the physics news recently because it is one of the technological approaches being considered to replace the prototype kg mass held in that Paris vault. Wiki: "As of 2011, the accuracy record is held by the U.S. NIST, with a relative uncertainty of 3.6 × 10−8 ..."

They use clever techniques to eliminate unknowns. It's those clever techniques that I was intending to point to with my mention of the topic. Basically, that 10-8 makes "0.1%" look pretty easy in comparison.

RE: Coil magnetic field measurement

(OP)
I see the point on watt balance and regarding accuracy, it surely can be used. It's just, that it would be easier to buy a sensor, rather than constructing one from scratch.

Well, the solenoid drives an analog electromechanical valve with really small movements.

RE: Coil magnetic field measurement

(OP)
The movements are about 100 micrometers.
As a summary my thoughts are:

Now I would like to choose between 2 options. There is the Hoeben Sensor, that I have linked before. This sensor is mounted on a circuit. The accuracy is a bit higher than 0,1%, as ohmic offset voltage / temperature can be corrected.(There is a manual for it on the website.) There are also the parasitic effects, IRstuff mentioned before.

The other option is a calibrated probe with a total accuracy of 0,1%. The link: http://www.senis.ch/docs/default-source/datasheet-...
Here I do not have to build a circuit, therefore the total accuracy may be better as in case 1.

RE: Coil magnetic field measurement

Before you get too involved in balances and such things: Do you need to follow the 7 kHz flux with high fidelity? Or is an RMS value good enough?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Coil magnetic field measurement

(OP)
RMS should be good enough. It's just that because of the electronics most sensors have a low pass behaviour.

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