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What is CTX3030? A VLF or a PI metal detector?
- Thread starter focus218
- Start date
Jason in Enid
Active member
It's actually a combination. It sending out a range of VLF signals, but interprets the responses like a PI. That's one of the reasons it's so hard to get non-users to understand how great the detector is. No other company besides Minelab does anything like this.
Johnnyanglo
Active member
The inner-workings of the CTX are well guarded. But from what I've read it sends out wave trains, short and long pulses, first at a low freq 3.125 (kHz) and then at a high freq 25.0 (kHz), sequentially. Next it measures the time constant of the decaying current in the target at each freq to determine the nature of the target. An iron target will borrow energy from the primary field and align its magnetic domains temporarily and then scramble them again ... which helps to reinforce the targets magnetic field longer than a non-ferrous target where the eddies spin is based on the metal (good conductor with high inductiveness will spin up the eddies and they want to spin longer due to more momentum). There are some subtraction schemes applied where early and late measurements at different frequencies are compared to determine target character. In any case, the CTX and E-Trac process the data differently than VLF machines which gives it better TID on deep targets and better depth in mod-to-heavy mineralized ground.
A PI is a bit different in that it builds up a large pulse and then the xmitter shuts off, then measures the time constant. It is more akin to a VLF machine but is unique in how it measures the demodulated signals. The drawback with post-processing of this nature is that you need to go slower when sweeping. You also need to realize that the base and harmonic freq used by the machine are the only freqs actually used (it xmits many more but they are wasted energy). The 25kHz harmonic isn't particularly high amplitude and doesn't carry as much power so the machine is really a very low freq machine. That is great thing for knocking out iron (ignoring it) but on low conductors (like thin rings, necklaces, and chains) it will either be completely gold dead or have a very limited sensitivity (depth can be less than 1" on a gold chain or the machine may not sense it at all). A single freq VLF detector will have a much sharper, tighter response on weak conductors to greater depths than the FBS machines. But you probably can't take your VLF machine near salt water (conductive) or in the water and submerge it (CTX). In heavy ground minerals the single freq VLFs lose depth quickly ... where the FBS continue to reach down (in some cases almost to the depth of a PI, but PIs don't know ferrous from non-ferrous very well) ... so there are advantages and disadvantages to detectors (they're just tools - use the correct one for the job).
But on higher conductors like silver, copper, and pure gold (which is rare) ... that it does very well and to great depth in harsh soil with better ID than most machines are capable of (again due to the way the returned signals are processed). You may also find that the E-Trac and CTX have more information portrayed on the screen in its Co-Fe values than most VLFs (which use a normalized X/R phase shift to determine the nature of the target). But in the end, you have to dig it to be sure ... so any Co-Fe value that falls within a known good area will have to be dug anyway. But you at least have a better chance at guessing the target ID than with a VLF single-line phase display (not to mention the more precise Disc settings on the CTX/E-Trac than those standard notch settings on VLF machines).
For all around use the CTX is hard to beat.
A PI is a bit different in that it builds up a large pulse and then the xmitter shuts off, then measures the time constant. It is more akin to a VLF machine but is unique in how it measures the demodulated signals. The drawback with post-processing of this nature is that you need to go slower when sweeping. You also need to realize that the base and harmonic freq used by the machine are the only freqs actually used (it xmits many more but they are wasted energy). The 25kHz harmonic isn't particularly high amplitude and doesn't carry as much power so the machine is really a very low freq machine. That is great thing for knocking out iron (ignoring it) but on low conductors (like thin rings, necklaces, and chains) it will either be completely gold dead or have a very limited sensitivity (depth can be less than 1" on a gold chain or the machine may not sense it at all). A single freq VLF detector will have a much sharper, tighter response on weak conductors to greater depths than the FBS machines. But you probably can't take your VLF machine near salt water (conductive) or in the water and submerge it (CTX). In heavy ground minerals the single freq VLFs lose depth quickly ... where the FBS continue to reach down (in some cases almost to the depth of a PI, but PIs don't know ferrous from non-ferrous very well) ... so there are advantages and disadvantages to detectors (they're just tools - use the correct one for the job).
But on higher conductors like silver, copper, and pure gold (which is rare) ... that it does very well and to great depth in harsh soil with better ID than most machines are capable of (again due to the way the returned signals are processed). You may also find that the E-Trac and CTX have more information portrayed on the screen in its Co-Fe values than most VLFs (which use a normalized X/R phase shift to determine the nature of the target). But in the end, you have to dig it to be sure ... so any Co-Fe value that falls within a known good area will have to be dug anyway. But you at least have a better chance at guessing the target ID than with a VLF single-line phase display (not to mention the more precise Disc settings on the CTX/E-Trac than those standard notch settings on VLF machines).
For all around use the CTX is hard to beat.
sorry I have turret's and it just comes out 
