I am trying to measure an oscillating magnetic field, of a solenoid and in the air gap of a transformer core. I have a Hall effect sensor, but its frequency range is limited, so I have put together a couple small coils which I connect to an oscilloscope to measure the field. The transformer core setup is within the frequency range (I have just been going to 40 KHz) of operation for the Hall sensor so I have used both and compared results to characterise a 3 turn coil's output voltage for given flux density. Similarly I have characterised the second coil 1 single turn based on measurement comparison with the 3 turn.
(Which in my mind seems like a sensible enough approach, and as the coils are the same radius and I got approx. 1/3 the output reading for the 1 turn compared to the 3 turn appears correct, but if I am mistaken please correct me).
I am running the solenoid at much higher frequencies (up to 20 MHz) and with a lot more power. I would like to know if I can assume that a coil set up for measurement has a linear relationship with field strength. The Hall sensor has a defined range for linear operation. I do not think this is the case for a measurement coil but I am not sure and would like to confirm.
And to ask whether the frequency of the magnetic field is something that needs to be factored in as well for my measurement?
Also, when trying to measure lower strength fields with the loops my output signal is very noisy. Why is this, and would it be improved with increased number of turns?
Any help, advice or tips would be appreciated.