The attached pdf it the results of my testing of the Feedback coil and Stan's Pulse indicator circuit.  The two screen shots below shot 2 examples of what the output of K14 signal H input in K21.  The also show that the K14's output level does not change with frequency.

The test report also show the 2 feedback coil outputs and how they change going through K14.  This is a simple circuit  and it is a standard circuit for an Op Amp with a gain of 10, which is set by the resistors. The diodes ensure the proper voltage +/1 is place on the Op Amp input pins.  The rest of items on the output are there to drive the led.

The 5v offset is removed by the Op Amp and is there so the Op Amp does not require a negative power supply, instead ground is used.

The gain of 10 is need to raise voltage level to that needed by K21.  Note:  Level is not critical as long as it is high enough.  The important part of the signal is the phase information.

My testing also show that winding the coil with halve the wire, adding 5V to center, then winding other half is not a problem, this is what I did.  I believe you could also add 5v to center then wind both halves at same time.

As you can see in the pictures below the feedback coils track the digital pulses.

I do want to note:  I did not use all the VIC coils for this test  I just used the Primary and Feedback coils.  The secondary was on the core but not hooked up.  My main purpose was to see what the feedback coil output looked like and to see what K14 did to the signals.  I think the testing accomplished those goals.

One side benefit for me was that have feedback coil and K14 in the system made the output of K21 much more stable.  Some of this due the present of the feedback loop on the Op Amp in the circuit which helps to eliminate noise, again a standard function of this type of circuit.

That's awesome Earl, many thanks for sharing

I hope you're considering showing a closed loop signal test aswell which shows the feedback coil affecting the PLL (assuming you're using a PLL to lock in on and maintain a preset frequency) which then keeps track on the output frequency & timing as the electric properties of the cell changes alongside with gas forming in cell cavities, etc etc :thumbsup:

Actually I am using the PLL system to generate the digital signal I used to power the feedback coil and and the output of K14 provides the sync information into the K21.  This was the first time I could fully test the PLL part of K21 and I was able to change change frequencies in K21.  I am now playing with the offset and gain setting to see what they do. I did find one thing I did not expect the lock function quit working around 775hz.  I could see this using both manual and auto modes. I can see the frequency stays locked as you can see from screen shot above.

I will report more on offset and gain tests in my Vic from pieces thread I started those tests.  I still have a lot of work before I get to full cell tests.

Sounds awesome Earl, looking forward to see what you find :thumbsup: