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Dave J- Question on CCPI

A

Anonymous

Guest
Hi Dave,
Finally got a chance to read and digest all you've written on CCPI. Sounds good from the standpoint of saving power, generating an approximate square wave without having to waste alot of power. Easy to do with a sine wave, not so easy with a square wave, and this does that. Very good!
My question is this, during phase II and IV when the coil is "shorted" to maintain the current flow, won't this shorted transmit coil, suck up all the energy from the decaying eddy currents in the target? Are am I not understanding something?
JC
 
The coefficient of coupling between the (shorted) transmit coil and the target is too miniscule for it to have an appreciable effect on target signal decay. However, it's rather obvious that the transmitter coil can't be shorted out and at the same time be used as a receiver coil, so an induction balance arrangement is necessary.
--Dave J.
 
Hi Dave,
Thanks for all the responses. I wasn't sure the receive coil would be able to receive the signal from the target with a shorted transmit coil so near to it. Energy from the target going into both, but more into the shorted one. Of course the coupling from the target to both of the coils is poor, so maybe it doesn't effect it as much as I might have thought.
Thanks again,
JC
 
In an induction balance arrangement, although the receiver is in close proximity to the transmitter, the fact of induction balance means that whatever is going on with the transmitter does not affect the receiver, to a first approximation. In commercial induction balance coils made for VLF metal detectors, the coefficient of coupling between transmitter and receiver is typically on the order of 1 part in 1,000.
--Dave J.
 
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