No subject just talking Whites detector stuff

[Roscoe]

I couldn't think of a subject for this post.

I was just thinking about the conductivity switch on the SPP and i thought to myself why don't they offer that feature on a VLF detector like the GMT or any other VLF detector. The conductivity switch is a useful feature with the TDI, SPP detectors. The way i understand it works on the Whites PI's is that any target that is above the ground balance point signals a low tone and any signal that falls below the ground balance point signals high tone? Is this how the PI works with its target tones?

Now if we had a VLF detector with same feature and you came across an area with a lot of negative hot rocks you could switch the conductivity switch to remove all negative ground signals and you wouldn't be pested by those signals, but still have the positive signals to detect gold.

Is it possible on a VLF? Would people find that useful?

Reg, maybe you could shed some light on my question.

 

[Reg]

Roscoe,

Your idea of the hi/low and the GB control setting point is correct. For those of you who don't understand, you can adjust the GB and change what becomes a high tone and what becomes a low tone. Take a large nail, at the normal GB, it will be a low tone. Adjust the GB down to 4 or 5 and the same nail becomes a high tone. A copper penny remains a low tone, while a small gold nugget remains a high tone.

One reason for adding the conductivity switch is you can ignore either tone or accept them, depending on how the conductivity switch is set. Tweak the GB when using the low setting so hot spots create a low tone and they will be ignored when in Low. Run this way and the only signals you will hear will be gold, lead, or other small metal objects. Certain mild ground can cause a low tone that won't be heard while in Low, but will cause a slow weak low tone when in All.

It can be confusing but remember, selecting LOW and only high tones will be heard. Select HIGH on the conductivity switch and only low tones will be heard. Select ALL and both tones will be heard. On SPP's that have not had the Conductivity switch added, act like the ALL position.

Getting back to Roscoe's question, unfortunately, VLF's work on a different principle where the signal into the ground is continuous. As such all objects create a signal and the signals are totally different than those of the PI. For example, a PI basically ignores black sand while most hotrocks cause a high tone at normal GB. There will always be some rocks that act differently, so there will be some that could create a low tone, but the typical pesky small red rocks will be high tones. Set the GB to ignore those rocks and most rocks will be ignored when in LOW.

VLF's can't do this simply because the detector is a frequency domain design and as such produces different responses than a PI. A PI is what is called a time domain detector, meaning a pulse is generated, shut off, and then time passes before a sample of the returned signal is taken. This repeats at about a 3000 cycle rate and the samples are all added and averaged, so they can produce a change when a target is under the coil.

So, the bottom line is the two detector designs differ dramatically and have different ways of operating. A VLF can be made to discriminate better. The TDI series relies on the idea objects that have a longer delay than the objects ignored at the present GB setting will create a low tone while objects having a shorter delay than the GB setting, will have a high tone. Unfortunately, weak responses are impossible to tell which tone is generated. The Conductivity switch will tell you because when you select the right setting, the tone will be heard while the other selection, the tone disappears. In all, or center position on the switch all tones are heard.

One last note, if you try to run with the GB off, you need to be in ALL or low mode or no sounds will be heard. With the GB off, all targets are high tones.

Reg

 

[Magilla]

Some great info there Reg, thanks for taking the time to explain.

 

[Roscoe]

Reg, I new you would know the answer to my question and thanks for the detailed reply. Well that definitely answered my question why the VLF detectors can't do the same as The Pi's. Its a shame it would be a great feature on a VLF if it could be done.