tones and vdi

[chub]

Forgive my ignorance. I read in some FTP instructions recently ( yes I read detector manuals for fun!) that the F75 has seperate circuitry for the audio tone and the VDI. Is this unique to Fisher / FTP or is this an industry standard? What are examples of machines where the audio and vdi numbers are the result of the same circuitry response?

Thanks
Chub

 

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[chub]

anyone reccomend another place to post this question?

Thanks
Chub

 

[b3y0nd3r]

I read this a few days ago, I thought some of the more technical members would of responded

USUALLY, There is one chip that has many input/outputs. Some outputs are audio, the other outputs can connect to a meter(or digital display) to give a VDI number. You can use separate chips to get more defined responses however, they would still need to be synced(so a high tone is equal to a high vdi(however, you can make it the opposite as well)).

As for some examples, Karl from Geotech would be your man. He is a very smart and capable person when it comes to the workings of a detector. He is a member here.

 

[sprailroad]

I am NOT, one of the more Technical members by any means, and as b3yOnd3r said, there are members on this Forum who are, and can most likely answer your question clearly. All I can say is based on my own experience, I use VDI #'s as perhaps a reference most often, and go (Most) often by sound. Example, recently while detecting with a Minelab Safari, I received a Iron type signal, ( a -2 on the Safari, in the Relic mode) but it DID briefly hit a high pitch with a "37" VDI, but returned to a -2, in pinpoint as well, normally I would have skipped it, but decided to dig anyway, and about 6" down, a 1943 Australian Penny the size of a Half Dollar, it was straight up on edge in side of hole. Point is I guess is VDI #'s are a help, and I always glance at them on screen, but sound is of more importance I think. OK, after having said all that, I too would like to hear from others in regard to your question out of curiosity.

 

[bigscoop]

Harmonics, this is what return signals become, some manufacturers/machines applying simple process to generate audio analysis of the returning sound waves that usually result in simple high, medium, low tones. On the other hand some machines/manufacturers use complex processes to generate a much wider scale of these high, medium, and lows. All of this, then, is also relevant in the generating of the numbers you see in the visual analysis of the number and/or image scale on a machine's target I.d. So the answer to your question isn't that simple as the same manufacturer can apply these different technologies to different machines, even machines in the same series, all of this usually being directly reflected in the cost of the machine.

By the way, even the coil design can play a role in how audio/visual target i.d. can be generated/processed, as can the various Pulse Induction, Single Frequency, and Multi-Frequency applications.

 

[chub]

Thanks Guys