I am working on a colpitt oscillator circuit which looks like this.

The tank circuit is completed by attaching an inductor coil to it. The inductance of the coil ranges in micro Henry. The aim is to find the inductance of the coil, through the frequency generated by the tank. I am measuring the frequency from the freq_out terminal. Everything works fine but I had a thought of finding inductance of more than one coil using the same circuit. To implement this, I have to somehow 'break' the connection of one tank circuit, temporarily, and 'make' connection with another (poposed) tank circuit. This ensures that one tank won't influence the other. But here comes the problem.

As both the start and end terminal of the tank (c_out to c1 and c2 to c_in), contains oscillation, I couldn't make a switch there using a device like a transistor. But the terminal between C1 and C2, contributes to potential difference (It provides the base of the transistor with the potential difference of C2), which can be switched using a transistor. I did this succesfully, and I am able to have two tank circuits parallel to each other. But both have influence over the other.

I thought of providing some kind of temporary isolation, which failed. I did some research but couldn't find anything interesting. The problem is, I have to isolate atleast one end of the tank, so that I can switch between two tanks within a small delay, and obtain different frequency values. Any suggestions?

 

From what you are saying, the freq of the circuit is about 1MHz.
This might be so, but there are a number of things that need to be adhered to.
The voltage is a bit low for reliable operation. The BC337 is not really designed for use in an oscillator, the 330n is very high and may dampen the tank circuit and you need to look into the fact that the energy stored in the capacitor (about 8n) has to equal the energy stored in the coil to produce an output about 2 x V

 

From what you are saying, the freq of the circuit is about 1MHz.
This might be so, but there are a number of things that need to be adhered to.
The voltage is a bit low for reliable operation. The BC337 is not really designed for use in an oscillator, the 330n is very high and may dampen the tank circuit and you need to look into the fact that the energy stored in the capacitor (about 8n) has to equal the energy stored in the coil to produce an output about 2 x V

I think the main problem is not addressed here. I know that the circuit is not perfect in terms of oscillations and energy loss. The main question is related to having two tanks in the same oscillator circuit, with only one of them functioning at a time. Something like switching over from one to another, so that we get two different frequencies, alternatively. I hope I made myself clear now.