P.I. Pulse Timing

[ericwd9]

Just what are the "Ideal" pulse timing considerations and coil construction and size for "small gold"

Pulse duration: It would seem that having a longer duration than that needed to saturate the coil is a waste of power?

Receive Delay: By experiment with my coil a delay of 8uS has been optimum. Sampling can occur at 5uS but was no improvement.

Receive duration: By experiment there was no real improvement over 5uS. 10uS resulted in more sensitivity to Iron with no improvement in small gold.

Pulse repetition rate: In my case 40uS. No change over range to sensitivity but "swing rate" impaired by longer delays.

Coil size: 8" Increasing size increased depth but only for larger targets.

Coil type: basket-weave litz as in: http://www.geotech1.com/forums/showt...eave-Litz-Coil

Detection range: 3mm 9k single gold chain link 2 1/2. Size 6 18k gold ring 4 1/2

Detector: Stuart P.I. II revisited as in: http://www.geotech1.com/forums/showt...I-PI-revisited

All timing is field programmable via micro switches.

I am interested what pulse timing is used by others.

Eric

[baum7154]

[QUOTE=ericwd9;205600]Just what are the "Ideal" pulse timing considerations and coil construction and size for "small gold"

Pulse duration: It would seem that having a longer duration than that needed to saturate the coil is a waste of power?

Receive Delay: By experiment with my coil a delay of 8uS has been optimum. Sampling can occur at 5uS but was no improvement.

Receive duration: By experiment there was no real improvement over 5uS. 10uS resulted in more sensitivity to Iron with no improvement in small gold.

Pulse repetition rate: In my case 40uS. No change over range to sensitivity but "swing rate" impaired by longer delays
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For what it is worth Chance PI has selectable Sample Delay down to 8us and that is what I use for small gold detection.

Receive Duration or A/D Sample Window is 12.5us long.

Pulse duration is more difficult to define as Chance PI uses a complex series of 16 small pulses with active coil shorting between each of the pulses followed by a 120us Long Pulse and then fly back. Total burst width is about 1.02 ms. This pattern is repeated at rate of 227 pps.

Regards,

Dan