Phase angles and all that jazz...........TheMarshall

[TheMarshall]

Hi there folks.....I've been reading the opinions posted regarding phase angles etc., and what they are supposed to indicate.

May I add my two cents worth to the debate.

I think I can safely say, that presently such phase indicators, be they in 'degrees' format or 'digitised numerics', are only a crude indicator of RELATIVE ground effect as sensed by the induction balanced search-coil arrangement.

You do not have sufficient data to make any accurate assessment of the quantitative mineralisation under the search-head.

At best, you are offered a 'general indicator'......A bit like licking your finger and sticking it in the air to check wind speed and direction.

Under such circumstances I offer the following:-

Let us invent some realistic figures by setting the search head's phase be 87 degrees, at frequency 'X', in air.

Now depending on the density of Fe mineralisation in the soil being tested, the phase will INCREASE as the mineralisation increases.

The actual resulting figure obtained is RELATIVE ONLY TO THE DIRECTION OF CHANGE, and tells us little about the MAGNITUDE of the Fe medium causing the change.

In that context, the phase change indicator is ambiguous, for it is dependent dynamically on TWO FACTORS.

Soil CONDUCTIVITY and Fe MINERALISATION.

A severe increase in the soil's conductivity will cause a DECREASE in the phase angle. ( Salt water or boggy, acidic ground, as examples).

So the reality of it all is that what we see numerically, is only a relatively crude indications of the ground's character.

The most significant thing being when there is an increase in phase, for this suggests that Fe mineralisation is present.

That in turn will cause a subtraction from the 'in-air' value of our targets, to a degree dependent on depth, size, conductivity of the metal involved and frequency used.

Also, mineralisation adds an unwelcome modulation to the base line signal, upon which our targets of interest ride.

Our choices of filters are intended to combat the latter.

Which one, is primarily (but not totally) dependent on your sweep speed.

So good people, the subject of phase readings, their significance, and interaction regarding filter choice, is a very complex subject.

At best we guess, using transient readings and knowing little of actual facts about the ground changes beneath our feet.

So ultimately, It's mostly about gaining experience of effect caused to the usual 'in-air' readings for the targets we recover,

and then trying to relate the differences, to form some simple, crude relationship to that thing we call 'Ground Phase'.

I almost forgot to also mention the limiting effect, (diversion) of flux penetration into ferrous mineralised soil.


TheMarshall........(UK adviser on White's detectors)...............

 

[hang7575]

So what you are telling us that the ground probe screen is worthless

 

[duclaw]

So what you are telling us that the ground probe screen is worthless

That's what I took from it too, but I can't imagine that is the case as I don't think White's would have put it in there if it was only a "crude indicator".

 

[Larry (IL)]

I think this is just a matter of having more information than we know how to use at this time. Let's re-evaluate this a year from now when books are written and more time is spent learning how to use the advanced tools that is available to us. I'm sure many of you are much like me, having loads of fun just finding stuff with the V knowing what we do.

For now, I suggest just trying the different filters and swing speed on a deep target or in your test garden to determine what works best for you in your ground. The half hour spent testing would be time well spent.

 

[duclaw]

Well put Larry. I agree that it is there for a reason and we simply haven't realized it's full value at this point....in due time!

 

[TheMarshall]

So what you are telling us that the ground probe screen is worthless

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~​

Worthless....???????????????????????

[size=large]Indeed NO.[/size]

Rather, that such data must be interpreted on the basis of how definitive it is, and YOUR comprehension of what it is telling you.

The point I was trying to convey, within the limited context of such a brief post, is that the Phase angle indication is not a 'complete' indicator.

It is only a PARTIAL factor of what should be a COMPLEX indicator. ( i.e. One which should contain other data.)

An analogy would be to compare the V3's Ground Phase meter, to a wind-vane

The wind vane indicates the direction the wind is blowing from, but not the strength of the wind.

It requires the extra information provided by the the 'spinning cups' on the more informative assemblies, which also tells you the wind's speed.

A navigator needs those TWO factors to predict his course.

So gentlemen, the important point is, 'How are you interpreting the data' as it is presently supplied?

My post was trying to alert you to understanding the present limitations involved, and also the problem of comments from those who do not.

The V3's data supplied by the ground probe etc., is an excellent source of dynamic monitoring.

The challenge now, is can YOU utilise it?

Whites have given you the 'tools', but can you develop the skills to use them?

Regardless of this discussion, the V3 is a superb detector, with a feast of functions in its menus.

Now it is up to you to enjoy the banquet.....................Have fun...........TheMarshall

 

[duclaw]

Thx Marshall, that sheds a new light on your first post.

 

[Skif]

Whites have given you the 'tools', but .... TheMarshall[/quote]

did not give any information how to use it

 

[ramases]

[
The challenge now, is can YOU utilise it?

Whites have given you the 'tools', but can you develop the skills to use them?

Regardless of this discussion, the V3 is a superb detector, with a feast of functions in its menus.

Now it is up to you to enjoy the banquet.....................Have fun...........TheMarshall[/b]

Now, while I accept the thrust of what you are saying here, in my view if we are going to get an understanding of what this information is telling us, it is really up to the Techies at Whites to help us with it. Otherwise, it is a bit like Ford adding a new switch to the dashboard of a car without explaining in the manual what it is for or offering any customer support when asked about it! Surely, someone at Whites understands what the Ground Probe is for and why it is useful - otherwise why bother to include it? Whites have a fantastic reputation for Customer Service and support so why nothing on this? Sadly, I am beginning to think that we'll have to wait for Mr Foster to publish his book before we get our heads around this one!