TDI discrimination

[Orbit]

But I realized at LOCATION 1, 2, 3, tdi has the effect of country I understand tdi only
One count ejects effect of country and only then has a high tone the gold coin ,peni coin ,a low tone on the iron object !position ground balance somewhere between 1 and 4 or 5 always produce a high tone from 4 or 5 up to 11 gives a low tone on all metals therefore tdi only in one position ejects effect of country ,also difference in tones respectively ,therefore the difference between low conductive targets and highly conductive targets achieves only in one position potentiometer graund balance ! whether I am right?? big greeting !

[Orbit]

No, delay is in us (10-25us), GB is an arbitrary 1-11. I don't know why that range was chosen. Edit: the GB knob adjusts the gain of the ground channel, not a timing parameter.

That is why there is no confusion !
GB knob adjusts the gain of the ground channel and it should be set One count where in fact nullifies the effect of country and gain variations
between highly conductive targets and low conductive targets !

[Orbit]

test! more realistic test, would be that positioned pot geb at one point ,where the effect ground where would exclusion ! and that potentiometer pulse delay turns ! and to monitor results testing !

[Orbit]

Hello whether so works tdi ???

[Geo]

At field test a good choise is delay = 10us and GB= near to 8. There is good ground balance and good depth. Other options... Delay=17.5 and GB=6 or Delay =23 and GB= 2...3.

[Geo]

Today i readed an old test of Minelab SD2200 by Reg. So i would like Reg to tell me how much deeper is sd2200 compared to TDI??

Regards

[maikl]

Hi Geo.
Tell me some information about the detection of TDI in air (for example coil 30cm):
-a can of cola 0.33l ?
-1 euro coin ?
-small gold earrings ?

[Geo]

See the table at post#16. Soda can is a 330ml.

[maikl]

Thank you Geo, I had not paid attention to that... you did not say that the coil was used and the smallest of gold is gold coin 22mm ... never tried a small gold earring?

[Reg]

Hi Geo,

I did that field test over 12 years ago and don't remember much now. Since then, I purchased a SD2200 but never took time to do much with it. The problem is, you can't use one in areas where you can use the TDI. The SD is simply works best in areas with no EMI.

At my home, I did test a couple of buried targets and found the TDI to do as well or better but this is because the TDI is better at ignoring a lot of noise. I can tell you that the TDI works better in many places because of the noise problem.

So, I can't tell you just how much deeper the SD 2200 will go in areas where there is no EMI because I never tried it away from noise sources except during that field test.

When the weather warms up and I get time, I will try to do more testing with the SD. I need to do that because I plan on selling the detector and I want to make sure it is working correctly before I do sell it.

Sorry I couldn't be more specific.

Reg

[Orbit]

Without electrical interference gs 4 the off position 1 euro grounding between 35 and 40cm , what's better tdi ?and use =for discrimination
dynamic embedded magnetometer in coil

[Geo]

Without electrical interference gs 4 the off position 1 euro grounding between 35 and 40cm , what's better tdi ?and use =for discrimination
dynamic embedded magnetometer in coil

I never had a GS4. I know that GS5 has the same performance with TDI. So why Eric to construct a detector not so good as the previous model???

[Geo]

Hi Geo,

I did that field test over 12 years ago and don't remember much now. Since then, I purchased a SD2200 but never took time to do much with it. The problem is, you can't use one in areas where you can use the TDI. The SD is simply works best in areas with no EMI.

At my home, I did test a couple of buried targets and found the TDI to do as well or better but this is because the TDI is better at ignoring a lot of noise. I can tell you that the TDI works better in many places because of the noise problem.

So, I can't tell you just how much deeper the SD 2200 will go in areas where there is no EMI because I never tried it away from noise sources except during that field test.

When the weather warms up and I get time, I will try to do more testing with the SD. I need to do that because I plan on selling the detector and I want to make sure it is working correctly before I do sell it.

Sorry I couldn't be more specific.

Reg

Hi Reg.
If you will make the test at "clear" area without EMI please inform me.

Thank you

[Reg]

Hi Geo,

Have you tried to detect the same coin on your TDI with the GB off and if so, what is the maximum distance you can detect it? Make sure you make this test away from any EMI noise, because such noise can cause serious depth loss. I suspect that if you use the maximum sensitivity setting and listen for a weak signal, you will find the depth comparable.

If there is any difference it will or should be minor but could be caused partly by the autotune circuitry. The autotune feature provides convenience and makes the detector very stable when compared to the original GS 4, but that feature does cause some minor depth loss. Remember, there is no autotune on the original GS 4.

Also, there may a very small loss because of the difference in the sample and hold circuitry. Again, the newer design is for convenience and simplicity.

These two features can be offset by adding additional gain to the later design. Unfortunately, this extra gain is impeded by the extra noise that comes with the extra gain.

If the GS 4 has the recommended addition of the autotune feature, then much of this gain is lost and I would suspect the differences to be minimal.

I have a GS 4 and don't find it to be more sensitive.

Reg

[Geo]

Hi Reg.
Of course i tried to detect the same coin with GB and without GB. There is a difference between 15... 20% favor of GB=off. I have modified a little the front end so now the ampification is about twice. When the place is clear of EMI i can give all the sensitivity. With any way (full sensitivity or not) the GB reduces the depth about 15... 20%. I speak about air test but i am not sure what is happening with a buried object because with PI detectors the depth is mystery!!!!.
I have a soda can (330ml) buried at 60cm depth two years ago. Other of my vlf detectots detect it at all metal mode, and other nothing at every mode. Tdi detects it with the coil up of the ground at least 30.... 35 cm, so we have 60 cm + 35cm =95 cm. But on air it detects the soda can at 75...80 cm max with GB=off.
What is happening????

Regards