Depth Readout Question

[Canewrap]

I've noticed a number of times that the depth showing on the machine (X-terra 70) seems all out of whack with the depth of what I recover. Is it possible that there is another target below the first that just doesn't register after the dirt has been disturbed? Will the machine pick up and register both targets, if they're right on top of each other, but seperated by a few inches? It just seems that at times the depth readout is reasonably accurate and other times, forget about it. I need some insight on this as its the only aspect of this machine that seems like it doesn't work all that well. I love using this detector otherwise.

 

[Mark in S.E. IA]

I have noticed that problem when the ground balance is not set right. The next time you see that happen, reground balance your MD'er and see if that helps.

 

[SteveP(NH)]

In order to calculate the depth of a target the software in the machine has to know what size the target is. Very few detectors can (or even try to) measure the size of a target. Usually most detector designers just use the assumption that a target is the size of a coin and use that to determine the depth. So targets smaller than a coin, say like a bullet is going to read deeper than it really is, while large targets such as cans will be more shallow than they read. This is common to all machines that don't have a system to explicitly measure the size of a target.

The scenario you mention where you have two or more targets under the coil can also cause problems as the detector will average the targets together.

Also the target needs to be centered directly under the coil to get an accurate reading even if its size is in the right ballpark. If it is off to the edge of the coil some then it will read deeper than it really is even being off by a small distance can affect the depth read out.

Finally, the Xterras seem to use the conductivity of the metal of the target as part of the depth read out, as I have noticed that when you are pinpointing and the target ID number drops then the depth read out will increase, so say a target reads an ID of 32 then while you are pinpoint the target ID drops to 22 then the depth read out will increase as well. So heavily corroded targets will read deeper than relatively clean (not corroded targets).

 

[Mtnmn]

It would be quite rare for your detector to not show if there was still another target in your hole after removing the first object. My X-T will often give both a coin and iron reading, if the coin is over top of the iron and somewhat off to one side of it. There are many things which can effect the depth reading of a target, among them are target size, material, angle, corrosion, depth and the amt. of time it has been in the earth. Ground composition, mineralization and moisture content or a combination of all of the above may effect your detector's depth reading on a target. As a general rule my targets are usually at less depth than indicated except for large deep objects which will sometimes register as being under 2 inches. Sizing them and then using my pinpointer will let me know if they actually are shallow targets.

 

[Canewrap]

Good stuff gentlemen, I really appreciate your insights and I will use them to see if I can get more accurate depth info in the future.

 

[SandPhantom]

My experioence has been pretty much as SteveP has indicated. GB being off and corroded coins seem to cause my depth readouts to vary.