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# Measuring Magnetic Field

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#### Catalyst

##### Full Member level 3
Hi all ,

I have a very stupid question to ask.

If I wanted to measure the magnetic field around a loop antenna how would i go about doing it and what equipment would I need. I'm not clear on the methodology

Any advice is much appreciated

Kind Regards

Cat

Update:

I've been looking at AC Gaussmeters because the magnetic field I wish to measure is alternating at frequencies between 1MHz and 30MHz. However, I can't find any equipment that operate at these frequencies.

Does anyone know of such equipment.

Is there another method where I can measure the magnetic field strength at these frequencies?

Any advice is much appreciated

Regards

Cat

I think you really need an instument to measure electromagnetic field, not pure magnetic.
Maybe selective voltmeter with calibrated antenna or something similar.

Could I measure the electric field intensity at these frequencies in the near field and then convert that to the magnetic intensity? If so, how would I go about the conversion ?

Kind Regards

Cat

Also,

Is it true that in the near field the relationship between E & H is far more complex?

Cat

There is this simple method comprised of 3 othrogonal coils (x,y,z) connected to a DVM.

EMF in the coils is proportional to the flux through these coils. So, all you need to get the magnitude of the magnetic field is to get the square root of x2+y2+z2. The only problem you face is that you'll need to calibrate this instrument first relative to a known refrence and the three coils are identical.

This is just an approximate method.

I assume you mean an RF magnetic field? A DVM will not respond in time.

You need some sort of coil that will pick up magnetic fields. If it is a fixed frequency you can tune out the coil to resonate at the frequency of interest, making the job easier. Then either hook up the coil to a spectrum analyzer, oscilloscope if the frequency is low enough, or a diode detector/log amp depending on the recieved power. You can rotate the coil to figure out the x,y,z component.

by Biff44

I assume you mean an RF magnetic field? A DVM will not respond in time.

You need some sort of coil that will pick up magnetic fields. If it is a fixed frequency you can tune out the coil to resonate at the frequency of interest, making the job easier. Then either hook up the coil to a spectrum analyzer, oscilloscope if the frequency is low enough, or a diode detector/log amp depending on the recieved power. You can rotate the coil to figure out the x,y,z component.

Thats what I'm trying to say. I was trying to say a sensetive detector but ended up saying DVM Thanks for calrifying Biff44

So for detecting a magnetic field at 15 MHz I would have to:

1. Make a loop antenna out of copper tubing.
2. Find its inductance with network analyser ( what other method is there? ).
3. Tune it with the relevant capacitance required to bring it to resonance at 15MHz
4. Connect the loop to a BNC or N-Type connector, 1 end of the loop connected to ground and the other to the inner conductor connection.

What next?

Regards

Cat

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