Critterhunter
New member
Ran across this interesting idea on setting the sensitivity in a very old post when doing some searching on another topic of interest to gauge various ideas on. Going to have to give it a try and see how I like this method...
That one I'm going to have to try. It sounds much like setting the ground balance via pumping the coil in a clean spot.
I always set my sensitivity setting for disc by the following method...
First I find a clean patch of ground wide enough to do a normal wide swing over by using PP mode to make sure no iron or other targets are present. Then I'll flip to disc and keep the coil still, either held in the air (but still horizontal, as raising it vertical can change the interaction with EMI) or on the ground in that clean spot. I'll then raise the sensitivity until I start to hear chatter or nulling. If I do then I know this is caused by EMI since the coil is not in motion and will lower sensitivity slowly until it stops. That eliminates the EMI aspect of setting sensitivity for me.
Then I start swinging the coil around (still in disc) in the same clean spot I found via PP before hand. If it starts to null or chatter I'll keep sweeping over the same spot to see if it's iron present I somehow missed with PP...If I slow down my sweep and it goes away then I know it's not iron but rather is caused by too fast of a sweep speed for my sensitivity setting. They are interrelated in some respects for me in my soil. Or sometimes a higher sensitivity setting requires a slower speed and a lower one allows for a faster sweep for me. Too fast of a sweep will also cause nulling out for the given minerals present. If it doesn't go away even with a slower speed, but comes and goes (nulling, etc) in the same spot, then I know it's too high a sensitivity setting, because a null or chatter from iron will always be there. I'll then lower sensitivity in small amounts until the random nulling or chatter goes away.
One other method I've used in the past and still do sometimes is to find a deep fringe target and then play with sensitivity until I get the most stable ID and tone out of it using long general "hunting for my next target" sweeps over it. I haven't really seen a lower sensitivity setting than max stable be needed with the 10" Tornado or 12x10, but in the case of my 15x12 I often found a lower setting than max stable gave me the best ID/hardest hit and right tone with a sensitivity setting a good bit lower than max stable. Only thing I can figure is that in my soil the 15x12 was just too big for the minerals present and would wash out a target at depth or degrade it badly if I made the ground signal too hot by cranking up the sensitivity even though the GT was still stable.
If I keep hitting nulls in large numbers, I'll stop and swing over some of those at a slower speed. If it goes away then that tells me my sensitivity is still too high for the ground matrix, or that I need to slow down my sweep for the sensitivity level I'm using. I prefer though to stick with a somewhat Whites medium speed as it often shows more depth on fringe stuff when I compare it to a slow one, so I'm more apt to lower sensitivity than to slow down to a turtle slow crawl. I've seen some say they get max depth in their soil with a crawl. Just not the case for my minerals at most of my sites. They seem to want a somewhat faster sweep. Seen one guy's video showing that was the case for him as well. A turtle slow crawl and the target would just disappear.
One thing I've seen a few say for them in the past and I found be true for me as well is that there seems to be a sweet spot in bad ground of pointing the sensitivity control right at about the "C" in noise cancel, or roughly around the 2 or 3PM setting on a clock face. More often than not when a site is really bad by the time I get it set where I want it I look down and see that the dial ended up being pointed right at that letter "C". More so with the 15x12 or the 10" Tornado though than the 12x10. It's rare for me to have to lower the sensitivity that low with the 12x10 due to minerals, but I have had to for really strong EMI situations.
When hunting old foot trails that have a lot of rocks in them which can cause a bunch of nulls, I've gotten so frustrated that I just set it to Auto and that usually smooths things right out. Don't need stellar depth in ground like that anyway. If the sensitivity setting gets much lower than say about 4PM then Auto usually gets the same depth for me. Not always though. I think that might depend on EMI and minerals present as to how low auto ends up setting it's self. I have dug silver at about 7.5" deep in Auto, and a few even silver quarters at worked to death spots I've creamed with many machines over the years.
Some of these weren't even masked but the ground was changing fast (hot rocks, black sand, iron patches, and then good clean neutral soil). I suspect that maybe auto might help in situations like that where the ground is changing so fast that a static manual setting might be too hot or too cold for the given patch of ground every few feet or so as it changes. Maybe auto is acting much like auto ground tracking in a sense where that can be beneficial in fast changing ground. I also suspect it helps in heavy iron patches to tame the machine down and see non-ferrous targets mixed in with the iron, but I need to play with that more versus manual on some badly masked stuff and see how that pans out.
PS- I have noticed one thing to watch out for when thinking I have sensitivity right. I'll be hunting along and then hold the coil still for several seconds and the threshold gets much louder all of a sudden. It's then I realized that the threshold had in reality dropped out while I was hunting due to too high of a sensitivity setting, but I had raised the threshold dial to where I could hear it again I would guess (not sure on that).
Try it some time...After swinging for a while hold the coil still and see if the threshold gets louder. Not by changing tone, but just it gets louder. If it does then that's a sure sign you've got sensitivity too high or were swinging too fast for the given minerals and yet were somehow still able to hear the threshold even with it dropping out while swinging. Probably due to the threshold dial being raised loud enough to hear again. Not seen this happen much so maybe it has nothing to do with the dial, but I do end up having to lower the threshold after lowering the sensitivity a bit to what the soil or sand is calling for.
Gary UK said:
That one I'm going to have to try. It sounds much like setting the ground balance via pumping the coil in a clean spot.
I always set my sensitivity setting for disc by the following method...
First I find a clean patch of ground wide enough to do a normal wide swing over by using PP mode to make sure no iron or other targets are present. Then I'll flip to disc and keep the coil still, either held in the air (but still horizontal, as raising it vertical can change the interaction with EMI) or on the ground in that clean spot. I'll then raise the sensitivity until I start to hear chatter or nulling. If I do then I know this is caused by EMI since the coil is not in motion and will lower sensitivity slowly until it stops. That eliminates the EMI aspect of setting sensitivity for me.
Then I start swinging the coil around (still in disc) in the same clean spot I found via PP before hand. If it starts to null or chatter I'll keep sweeping over the same spot to see if it's iron present I somehow missed with PP...If I slow down my sweep and it goes away then I know it's not iron but rather is caused by too fast of a sweep speed for my sensitivity setting. They are interrelated in some respects for me in my soil. Or sometimes a higher sensitivity setting requires a slower speed and a lower one allows for a faster sweep for me. Too fast of a sweep will also cause nulling out for the given minerals present. If it doesn't go away even with a slower speed, but comes and goes (nulling, etc) in the same spot, then I know it's too high a sensitivity setting, because a null or chatter from iron will always be there. I'll then lower sensitivity in small amounts until the random nulling or chatter goes away.
One other method I've used in the past and still do sometimes is to find a deep fringe target and then play with sensitivity until I get the most stable ID and tone out of it using long general "hunting for my next target" sweeps over it. I haven't really seen a lower sensitivity setting than max stable be needed with the 10" Tornado or 12x10, but in the case of my 15x12 I often found a lower setting than max stable gave me the best ID/hardest hit and right tone with a sensitivity setting a good bit lower than max stable. Only thing I can figure is that in my soil the 15x12 was just too big for the minerals present and would wash out a target at depth or degrade it badly if I made the ground signal too hot by cranking up the sensitivity even though the GT was still stable.
If I keep hitting nulls in large numbers, I'll stop and swing over some of those at a slower speed. If it goes away then that tells me my sensitivity is still too high for the ground matrix, or that I need to slow down my sweep for the sensitivity level I'm using. I prefer though to stick with a somewhat Whites medium speed as it often shows more depth on fringe stuff when I compare it to a slow one, so I'm more apt to lower sensitivity than to slow down to a turtle slow crawl. I've seen some say they get max depth in their soil with a crawl. Just not the case for my minerals at most of my sites. They seem to want a somewhat faster sweep. Seen one guy's video showing that was the case for him as well. A turtle slow crawl and the target would just disappear.
One thing I've seen a few say for them in the past and I found be true for me as well is that there seems to be a sweet spot in bad ground of pointing the sensitivity control right at about the "C" in noise cancel, or roughly around the 2 or 3PM setting on a clock face. More often than not when a site is really bad by the time I get it set where I want it I look down and see that the dial ended up being pointed right at that letter "C". More so with the 15x12 or the 10" Tornado though than the 12x10. It's rare for me to have to lower the sensitivity that low with the 12x10 due to minerals, but I have had to for really strong EMI situations.
When hunting old foot trails that have a lot of rocks in them which can cause a bunch of nulls, I've gotten so frustrated that I just set it to Auto and that usually smooths things right out. Don't need stellar depth in ground like that anyway. If the sensitivity setting gets much lower than say about 4PM then Auto usually gets the same depth for me. Not always though. I think that might depend on EMI and minerals present as to how low auto ends up setting it's self. I have dug silver at about 7.5" deep in Auto, and a few even silver quarters at worked to death spots I've creamed with many machines over the years.
Some of these weren't even masked but the ground was changing fast (hot rocks, black sand, iron patches, and then good clean neutral soil). I suspect that maybe auto might help in situations like that where the ground is changing so fast that a static manual setting might be too hot or too cold for the given patch of ground every few feet or so as it changes. Maybe auto is acting much like auto ground tracking in a sense where that can be beneficial in fast changing ground. I also suspect it helps in heavy iron patches to tame the machine down and see non-ferrous targets mixed in with the iron, but I need to play with that more versus manual on some badly masked stuff and see how that pans out.
PS- I have noticed one thing to watch out for when thinking I have sensitivity right. I'll be hunting along and then hold the coil still for several seconds and the threshold gets much louder all of a sudden. It's then I realized that the threshold had in reality dropped out while I was hunting due to too high of a sensitivity setting, but I had raised the threshold dial to where I could hear it again I would guess (not sure on that).
Try it some time...After swinging for a while hold the coil still and see if the threshold gets louder. Not by changing tone, but just it gets louder. If it does then that's a sure sign you've got sensitivity too high or were swinging too fast for the given minerals and yet were somehow still able to hear the threshold even with it dropping out while swinging. Probably due to the threshold dial being raised loud enough to hear again. Not seen this happen much so maybe it has nothing to do with the dial, but I do end up having to lower the threshold after lowering the sensitivity a bit to what the soil or sand is calling for.