Reference frequency In my experiment, I have to obtain a relation between magnetic field of a solenoid and the applied Vp-p. 
The setup is as follows.

http://www.teachspin.com/instruments/faraday/

Does my choice of reference frequency, in such an experiment where the slope of the obtained graph (B versus Vp-p) is dependent on the frequency, matter? I did it with three different values but then proceeded with the experiment with just one of them for no particular reason whatsoever. So I am not sure as to how to explain my choice of reference frequency (out of 800 Hz, 900 Hz and 1000 Hz, I chose 800 Hz for the subsequent parts of the experiment).
 A: You can answer your own question by running the experiment with the other two frequencies!  If you obtain the same results, then the frequency does not matter.  If the results are different, then it does.
Actually, I am surprised that you are using AC, I think DC would be more appropriate.  From the picture of the device, I see that it has red and black power posts.  Red is typically the +, and black is the - polarity.  
A: The measurement frequency doesn't matter to the Faraday effect at the frequencies you mention (though it might at high RF frequencies).  The choice of frequency could matter to the electrical circuit which you are driving the solenoid with though.  This is because a solenoid is essentially a large inductor, and circuits with inductors can have resonances.  If you are near one of these resonances then you can get an amplification of the field strength which would cause the effect to be stronger.  It is likely that the inductance isn't high enough for the resonant frequency to be at such low frequency, but I can't say for sure without knowing the value.  
