Posted by PakProtector [ 64.12.116.134 ] on March 28, 2006 at 19:57:40:

Hey-Hey!!!,
In order to determine the resonant frequency some means of determinimg the maximum impedance of the choke is needed. With a 'scope and sine wave generator and a sense resistor it is fairly easy.

Arrange a series circuit with the choke and resistor. resistor to ground of the signal, choke to the positive. With the 'scope one channel on the resistor( ground to ground ), and the other across the whole thing. Again, ground to ground.

As the choke reaches a maximum impedance the voltage across the resistor will reach a minimum. Probably best to pick a non inductive as well as low capacitance. I used a metal film IRC GS-3. A carbon composition would probably be best.

It is a lot easier to detect a small change in a small signal than it is to detect a small change in a large signal. So we pay particular attention to the small voltage across the resistor. The full circuit is monitored to insure that the source voltage is not changing.
cheers,
Douglas

Replies: