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Recovery Delay (old link)
Posted by: Rob (IL)
Date: November 15, 2014 03:21PM
Estimating Optimum Recovery Delay Settings
There are a lot of details in the explanation below, but first here is the simple answer. To determine the optimum RD in terms of masking, lay two coins a tad more than one coil's width apart and pass the coil over the targets at 3 – 4 inches height at your swing speed and adjust the RD until you can hear both coins. Giving Spectra "all the time it needs" (but no more) is the right answer.

Recovery Delay settings are just as the name implies - the delay time that you are imposing on Spectra before it can process a second target after the first target has been processed. I like to use the analogy that a target is processed in four steps.... (1) Target is acquired
(2) Target data is calculated
(3) Target data is displayed
(4) Target is released and housekeeping done in preparation for the next target. Steps 1 - 4, added together = Recovery Delay.

Lower numbers = SHORTER delay. Higher numbers = LONGER delay.
Too much RD = Masking. Too little RD = depth loss.

(1) The coil can't see anything before or after it is over the target (discounting edge effect)
(2) A full coil width's separation will minimize masking, actually a tad more than a coils width to address edge effect.

(3) Faster RDs are best deployed in high trash areas.

(4) Slower RDs will provide more depth, up to the point that the coil is no longer over the target.

As you INCREASE Recovery Delay for a given size coil, you should SLOW DOWN your sweep speed. The LONGER the delay the SLOWER the sweep should be. If you decrease the size of the coil, you should DECREASE the Recovery Delay and slow down your sweep speed.

The optimum Recovery Delay for a given sweep speed is one that will give you two signals on two targets that are one coil's width apart. If you pass over a dime and then hit a quarter that is less than 1 coil-width away, you might see the quarter if the RD signal is far enough down on the decay ramp and the quarter signal is strong enough to over-ride the RD at the current delay point.

"Everyone has an opinion, but mine is free":devil:
"You might very well think that; I couldn't possibly comment..."

Edited 1 time(s). Last edit at 11/15/2014 03:22PM by Rob (IL).

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