I did more tests in the yard (in real dirt in the ground now) this week looking at depth indicator accuracy vs target and depth with the 505. I collected 7 data points per target over depths of 0 to 6 inches and recorded the indicated depth, IDs, and minimum sensitivity required to hit on the target. Targets were one gold band, silver 1/2, indian head, silver ring, quarter, and a nickel. The 505 indicated the depth with symbols with an accuracy of +/- 2 inches (not too great with a tendency to overestimate). However, for all targets, the actual depth was accurately indicated over the entire depth range studied (accuracy within 1/2 inch) by the minimum sensitivity divided by 2 (very linear relationship). All other settings were irrelevant (noise cancel, threshold, ground balance, volume, all metal ). Increasing ground balance above the set value (10 in my yard) did give a more definite target signal than the setting determined per the manual. For example, at minimum sensitivity at set GB the 505 was hitting on ~75% of the swings. Increasing GB as much as 15 (to a new setting of 25) caused the 505 to hit on 100% of the swings. However, I could not then decrease the sensitivity to a lower setting and still hit the target. This indicated that tweaking GB a significant amount had little, if any (1/2 inch or less), impact on actual depth but did give clarity to the signal. There was a limit to this benefit as GB set too high induced falsing. What I found most surprising was that all targets I looked at behaved exactly the same with respect to depth and sensitivity regardless of their size and composition. At a given sensitivity, big silver was not detected any deeper than the indian head. Note that none of my targets were big iron pipes etc which sure seem to hit deeper than just about everything else.
Numeric IDs this time all drifted up as depth increased (this is completely opposite of what I saw in previous tests ... once in potting soil in a bucket and once very limited in the ground where IDs dropped like a rock as depth increased). All targets this time hit at 45-48 at 6 inches except the nickel which topped out at 39-42-45. My ground is moist with a high percentage of clay. I was not able to "dial in" the IDs by adjusting any of the detector's settings. IDs do not always shift but I suspect when you see an abnormal ID for one target (in the absence of interference from nearby targets), it is probably safe to assume a similar shift is occurring with all targets at a similar depth.
Tests this time were done no closer than 50 feet from any metal (fences) and several hundred feet from any power lines. Tests are still in nested PVC tubes sunk in the ground at an angle. (This means if a target was 4 inches deep, it had about one inch of air immediately above it and three inches of soil). This could easily skew the actual sensitivity/depth relationship.
I am interested in knowing if any other 505 users can confirm the sensitivity/depth relationship or maybe indicate where it falls apart (and it might fall apart more than not.) I did some limited detecting today and it seemed to hold up well at a local park. It might be useful for others.
Cheers,
S505
Numeric IDs this time all drifted up as depth increased (this is completely opposite of what I saw in previous tests ... once in potting soil in a bucket and once very limited in the ground where IDs dropped like a rock as depth increased). All targets this time hit at 45-48 at 6 inches except the nickel which topped out at 39-42-45. My ground is moist with a high percentage of clay. I was not able to "dial in" the IDs by adjusting any of the detector's settings. IDs do not always shift but I suspect when you see an abnormal ID for one target (in the absence of interference from nearby targets), it is probably safe to assume a similar shift is occurring with all targets at a similar depth.
Tests this time were done no closer than 50 feet from any metal (fences) and several hundred feet from any power lines. Tests are still in nested PVC tubes sunk in the ground at an angle. (This means if a target was 4 inches deep, it had about one inch of air immediately above it and three inches of soil). This could easily skew the actual sensitivity/depth relationship.
I am interested in knowing if any other 505 users can confirm the sensitivity/depth relationship or maybe indicate where it falls apart (and it might fall apart more than not.) I did some limited detecting today and it seemed to hold up well at a local park. It might be useful for others.
Cheers,
S505
