UK Pre decimal Coin Depth test.:ukflag:

[Mr-depthtester]

Hi my name is cliff gold and today i decided to do a coin depth test in a garden with a detech 8 inch excelerator coil. The Detector i was doing the depth test with was the minelab explorer SE. The coin was a UK pre decimal penny this is a large coin. The Soil is highly mineralised.
A 7 inch deep plug was cut and the old penny was placed as flat as possible in the bottom of the plug hole, the plug was refitted over the hole and trampled down flat. I scanned over the hole with the SE set to the factory coins setting to see what kind of response i would get , i could not get any response at this depth not even a whisper so i took the plug back out and re buried the penny at about 4.5 inches , i now got a signal that would hit from one sweep angle only , i rotated 90 degrees and still could only get a one way signal , the cross hair did hit towards upper right corner but jumped about between the edge of the blacked out discriminated out section on the left and then would jump towards the clear section close to the top right corner. This is a signal that would be considered slightly iffy and could be missed if not careful.Slightly Beyond 4.5 inches the signal got so bad the target would be missed real easy by many users. Tomorrow i will try the standard minelab SE coil on this 4.5 inch deep penny and see if the response is any better , i will post my results here for all to view , switching to all metal made no difference to the quality of the signal and no increase in depth was noticed by switching to all metal mode. Deep on also made no noticeable difference. More depth test results to follow within the next few days. This proves that freshly buried targets or targets such as coins in fresh ploughed soil will give no more depth than 4.5 inches if the soil is highly mineralised.

 

[Mr-depthtester]

Hi my name is cliff gold and today i decided to do a coin depth test in a garden with a detech 8 inch excelerator coil. The Detector i was doing the depth test with was the minelab explorer SE. The coin was a UK pre decimal penny this is a large coin. The Soil is highly mineralised.
A 7 inch deep plug was cut and the old penny was placed as flat as possible in the bottom of the plug hole, the plug was refitted over the hole and trampled down flat. I scanned over the hole with the SE set to the factory coins setting to see what kind of response i would get , i could not get any response at this depth not even a whisper so i took the plug back out and re buried the penny at about 4.5 inches , i now got a signal that would hit from one sweep angle only , i rotated 90 degrees and still could only get a one way signal , the cross hair did hit towards upper right corner but jumped about between the edge of the blacked out discriminated out section on the left and then would jump towards the clear section close to the top right corner. This is a signal that would be considered slightly iffy and could be missed if not careful.Slightly Beyond 4.5 inches the signal got so bad the target would be missed real easy by many users. Tomorrow i will try the standard minelab SE coil on this 4.5 inch deep penny and see if the response is any better , i will post my results here for all to view , switching to all metal made no difference to the quality of the signal and no increase in depth was noticed by switching to all metal mode. Deep on also made no noticeable difference. More depth test results to follow within the next few days. This proves that freshly buried targets or targets such as coins in fresh ploughed soil will give no more depth than 4.5 inches if the soil is highly mineralised.
Depth test update
I did a depth test today on this old penny with the stock minelab 10 inch coil to compare with the 8 inch detech coil , The signal with the minelab 10 inch coil now repeated clearly and loudly from left to right and would repeat with the coil raised 1.5 inches from the ground so this gives an extra 1.5 inches approx extra in ground detection depth by using the 10 inch coil as opposed to the detech 8 inch. I rotated 90 degrees and re swept the hole however i could get no response no matter how close to the ground the coil was placed , i rotated a further 90 degrees and the signal repeated nicely , i guess maybe a small bit if iron was the reason it would not repeat from all angles or maybe the coin was tilted slightly i am not sure. Just as an experiment i decided to see how reducing and increasing sensitivity level would affect the signal response , i turned sensitivity down from the semi auto 22 setting to semi auto 10 and noticed no difference in signal response , the signal only started to get crappy when set to below 10 so this proves that depth is not affected hardly at all unless you drop sensitivity to below 10. Increasing sensitivity all the way up to 30 also made hardly any difference to the response of the coin it was more or less the same, if there was any difference it was hardly noticeable. No way could i get the coin to repeat from all angles using any combination of settings . Using all metal mode also did not increase the signal response/depth over the coin. So all in all for the deepest coins use the 10 inch coil which will give you 1.5 -2 inches extra depth on large coins. Search areas of land in a criss cross method because many targets will only repeat from certain sweep directions. Also fast on or deep on seem to make no noticeable difference to the response of deep coins , maybe their is a small difference but i honestly could tell no difference. Remember this soil is highly mineralised in low mineralised ground i am sure you could double this coin detection depth of 6 inches with the standard coil. Also i noted that the depth meter read about 9 inches deep on this 4.5 inch deep old penny so it appears that on large coins the depth meter is not no where near as accurate as i first thought.

 

[NealNoIN]

Getting a repeatable signal then at 90 degrees getting the signal only one way usually means iron. It would be interesting to see what would change if you got that piece or pieces of iron out of the way.
If you had an X-1 probe and used the pinpoint button(all metal) you could find the iron and remove it. I would bet you could add some inches to your depth test then. Also, any metal detector's depth guage will change dramatically when the size of the coin changes but I'm confused on your depth reading. It's just the opposite of what it should be. A larger coin should read shallower than it's actual depth. Are you sure you had the coin pinpointed for that depth reading? Also was the 9 inch reading with the 8 inch or 10.5 inch coil?
Thanks,
Neal

 

[Mr-depthtester]

The depth reading was with the 10 inch coil , i got the exact center of the coil over the coin and the reading fell at 9 inches at least i was surprised yes. i will recheck it later on just to make sure.

 

[Chris(SoCenWI)]

When you get a signal that is fine from one direction and not there 90 degrees apart it means you have a nail masking the target. Put a nail onto of a coin and try detecting in when it is not buried; you'll get the same results.

I bet if you tried in another area and made sure there was no iron you would get much greater depth. Turning the sensitivity up and down in Semi-auto does almost nothing; the detector sets it where it wants. Go to manual and now you will see a huge difference when you vary the sensitivity.

 

[Mr-depthtester]

I have to disagree with you there about manual sensitivity making a huge difference , i have tried adjusting manual sensitivity all the way up and right down to 10 manual , the response is almost the same , no extra depth is noticed on my buried coin. People think that increases in depth can be made by winding up the sensitivity but tests have shown only a little extra depth at most can be obtained by winding up sensitivity from say manual 22 to manual 30 . Don't take my word for it if you don't believe me then try it your self , you will be lucky to get half an inch extra depth by increasing sensitivity from say manual 22 to manual 30 . I can say this is very true at least in my soil . Do this simple test , bury a coin and make sure its laid flat at about 5 inches , now sweep over the coin with different sensitivity levels , first at manual 22 then increase to manual 30 ,you will see very little "extra depth". I am not pulling the explorer SE down i love the detector but i have tried this test with SE & detectors other than the explorers and have always got the same results , the detectors are set pretty close to the limits of detection depth when they come from the factory. Plus there is virtually no difference in depth between any of the top of the range detectors , i say virtually because some may have a very slight depth advantage over other models but we are only talking a few Cm's at best on say a coin sized target.

 

[Mr-depthtester]

I re scanned over the hole with the 4.5 inch deep old pre decimal penny just to re check the depth readout , today the reading was exactly half way on the depth scale which equates to a depth reading of six inches ,so on a large coin the meter is only 1.5 inches reading deeper than the coin is actually buried , i am not sure why the reading is different today, yesterday it read 9 inches. Today i buried a pre decimal half penny at 7 inches just to see what the response was on this smaller coin , this coin is what i would class as a medium sized coin , Scanning over this 7 inch deep pre decimal half penny i can just about get what is without doubt an "iffy signal" but you have to know its there otherwise it would be missed by many users, new users would pass over this signal i am sure , scanning very slowly i can get the signal and would normally dig it , sweep slightly faster though and the coin stays very quiet and would be missed by most with a normal search speed. I think at 6 inches most people would get a good enough response to not miss this pre decimal Victorian half penny coin. Past 6 inches it seems that the signals coins give drop off fast with regard to the strength and quality and start to get really iffy at 7 inches and this is with fairly big coins. I have not found a coin deeper than 7 inches out in the field (as yet) this is because i hunt plough land mostly. On settled ground like pasture i guess about 8- 10 inches max would be just about the best i could get on a medium sized coin. Maybe a foot on a big coin but only a maybe i have not found one at this depth so i don't know for sure.

 

[Steve(MS)]

Another thing to consider is whether there are iron targets below the plug you did for your testing, that can cause not being able to get the best signal.

 

[Mr-depthtester]

Yes i agree something is close to the coin maybe a small lump of coke , i will re check the hole i am sure some iron or coke is close to the coin or under neath , i tried to check in all metal for co located ferrous maybe i have missed the small ferrous hiding close by!