EMI effect

I read a Wiki article on EMI . It lists hundreds of sources including the sun and solar radiation. My question is, does EMI affect all detectors the same or say like does the sun or phone towers affect one certain brand or model different than another? I know Mr. Dankowski told of air testing with a dime between different detectors in one certain situation and picking the one that could discern 10 inches when a different one couldn’t. Does this prove that one is deeper than the other in all situations or can the one that didn’t test as deep that day test deeper another? With all the different forms of EMI, is there any way to say one is deeper than another?

A lot depends on how the machine was designed..... does it have the ability to compensate for EMI and how well does it do it. Theres a whole lot that goes into the "depth factor". EMI is just a very small part of it... minerals (salt and ground phase), type of target, how well it can unmask, moisture ability, Components of the detector, coil, headphones, and on and on.... and then there is YOU. Coin garden is one of the most reliable for comparisons...... but even that aint going to tell you what you might get at a given location.



Edited 1 time(s). Last edit at 04/30/2019 07:12PM by dewcon4414.

Every different model of detector is looking at the received signal differently. The EMI that degrades performance for an AT-Pro may do nothing to a White's V3i (just random models for illustration) and vise-versa. One of the things discovered from Minelab multifreq detectors was that you can get different performance from different frequency "channel" on different days. Where as Channel 3 may give the best depth today, tomorrow it might be channel 7. So obviously, the frequencies used and listened to can be negatively affected by transient EMI.

The worst part is that so much of the world we live has "silent EMI" that is affecting our detector performance but not so severely that it produces audible signals. This is why Minelab's owner manual for FBS and newer models say to perform a noise cancel every time you turn on the detector and possibly multiple times during a long hunt.

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You can see my videos here: [www.youtube.com]
My blog is here: [thesilverfiend.com]

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Among EMI........weather, barometric pressure, ground moisture, even battery level will affect a MD performance. A lot of variables will affect overall performance....everyday is different. Not to mention the user's skill or current mental state.....LOL. Will lend to the fact that no site is completely dug of targets. If finds get more sparse try a different coil.....shape, size, or type (dd or concentric).

Picketwire Wrote:
-------------------------------------------------------
> I read a Wiki article on EMI . It lists hundreds
> of sources including the sun and solar radiation.
> My question is, does EMI affect all detectors the
> same or say like does the sun or phone towers affe
> ct one certain brand or model different than anoth
> er? I know Mr. Dankowski told of air testing with
> a dime between different detectors in one certain
> situation and picking the one that could discern 1
> 0 inches when a different one couldn’t. Does th
> is prove that one is deeper than the other in all
> situations or can the one that didn’t test as dee
> p that day test deeper another? With all the diff
> erent forms of EMI, is there any way to say one is
> deeper than another?


Depth of a detector.
Has some different meaning really.
I look at depth as how deep a detector will identify nonferrous as nonferrous.
It will depend on target though as to how deep as well as ground mineralization.
Some detectors do better as ground minerals rise. Key word is is better. All VLF detectors are negatively affected.

EMI
We can’s see it, smell it or feel it.
A detector can be affected by it though.
How much it’s affected will vary.

How much Emi affects depth will vary.

Seems multi frequency detectors generally fair better in situations where Emi would be more obvious.
The noise cancel features, of Minelab GPX series (pi) detector models, Garrett ATX (pi) detector model, Minelab fbs/fbs2 VLF detector models, Minelab Equinox series (Multi IQ ) all have the noise cancel feature. By all accounts this noise cancel feature does a good job overall. A user doesn’t usually have to monitor audio feedback in gauging Emi being present at particular freq the detector is being used.

Emi can change while a detectorist is in a site too.
In my rural area aircraft pose as an Emi source.
I can sometimes while detecting even using Minelab Equinox when an aircraft in vicinity is affecting my detector.
Naturally other detectors being operated nearby can be a source of Emi.

It is recommend by some to find a somewhat deep target when using a detector not equipped with noise cancel feature and compare how the detector responds while changing channels (off setting the freq) and see if one can find a channel where the detector seems to give best signal.

Some detectors by virtue of their engineering are more prone to Emi. Good example here is original Fisher F75 units. Later on Fisher started equipping their F75 models with what they refer to as digital shield technology (DST). This new addition defintley made the detector line less Emi prone.

I really like the noise cancel feature of the Minelabs.
It is my opinion any and all flagship detectors manufactured should have this noise cancel feature.
Handy and saves time. And seems does improve actual infield performance over time.

Cheers.



Edited 2 time(s). Last edit at 05/01/2019 11:26AM by tnsharpshooter.

Is the noise cancel feature similar to the different frequencies in the F75 and T2 except the Minelab finds the frequency by itself?

Yes

Seems the Minelab noise cancel has a wider range as I can audibly hear the differences.....when it picks a channel, it is quiet. The f-75, seldom can I tell of a difference when switching channels, they are all equally noisy. But then again, my f-75 is more sensitive to smaller pieces of metal verses the FBS units.
In some areas the f-75 will almost stop chattering once the coil is swung over the ground.

Picketwire Wrote:
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> Is the noise cancel feature similar to the differe
> nt frequencies in the F75 and T2 except the Minela
> b finds the frequency by itself?


Here’s a video I did. Very relatable to your questions in original post here.

[m.youtube.com]



Edited 1 time(s). Last edit at 05/01/2019 11:34AM by tnsharpshooter.

Thank you for the video. I appreciate it.

Yes EMI is very real.

Silent EMI is the KIller

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

If you do suffer from EMI on a regular basis chances are it will be at 'its worst' from around 12 midday to 6, or 7pm when most forms of 'transmissions responsible' are slowly wound down.
As the day gets on with its business and more machines / trains / engines are 'on', it will be at its worst. Best times w/o EMI would be 7am and 7pm when most folks are 'shut down' and gone home for the day because it's industry in its many varied forms is responsible for 'heard' EMI
Heck, you can even get it in 'rural idylls' when a tractor or combine is switched on: many's the time I have heard a generator in an engine being fired up thru the speaker/headphones in the middle of nowhere with just 'birds' singing and nowt else!



Edited 1 time(s). Last edit at 05/03/2019 02:04PM by Des D.

Is there any way to tell what kind of EMI or the level of it with which to experiment? Example: Is there any way to tell if my Super Duper 800 works better than my Z99 in EMI caused by cell phone towers but my Z99 is better with electrical lines overhead and can I measure the different levels to know which one is the most likely to be successful?

Arkansas Wrote:
-------------------------------------------------------
> Among EMI........weather, barometric pressure, gro
> und moisture, even battery level will affect a MD
> performance. A lot of variables will affect overal
> l performance....everyday is different. Not to men
> tion the user's skill or current mental state.....
> LOL. Will lend to the fact that no site is complet
> ely dug of targets. If finds get more sparse try a
> different coil.....shape, size, or type (dd or con
> centric).


Please explain how barometric pressure effects a metal detector. That's a new one on me.

glabelle Wrote:
-------------------------------------------------------
> Arkansas Wrote:
> --------------------------------------------------
> -----
> > Among EMI........weather, barometric pressure, g
> ro
> > und moisture, even battery level will affect a M
> D
> > performance. A lot of variables will affect over
> al
> > l performance....everyday is different. Not to m
> en
> > tion the user's skill or current mental state...
> ..
> > LOL. Will lend to the fact that no site is compl
> et
> > ely dug of targets. If finds get more sparse try
> a
> > different coil.....shape, size, or type (dd or c
> on
> > centric).
>
>
> Please explain how barometric pressure effects a m
> etal detector. That's a new one on me.


Yes barometric pressure can affect Emi a detector is exposed to. Meaning the Emi source (emitter) could be more enabled or less enabled for detector affects. A TV using antenna and tv. I could tell when weather was high pressure or low pressure. As far as reception went.
This here a good read. Weather phenomenon could cause emitter on aircraft (farther away from you) for example to have more dire effects on your detector vs average.
[pnrsolution.org]



Edited 2 time(s). Last edit at 05/04/2019 01:26AM by tnsharpshooter.

Des D Wrote:
-------------------------------------------------------
> If you do suffer from EMI on a regular basis chanc
> es are it will be at 'its worst' from around 12 mi
> dday to 6, or 7pm when most forms of 'transmission
> s responsible' are slowly wound down.
> As the day gets on with its business and more mach
> ines / trains / engines are 'on', it will be at it
> s worst. Best times w/o EMI would be 7am and 7pm w
> hen most folks are 'shut down' and gone home for t
> he day because it's industry in its many varied fo
> rms is responsible for 'heard' EMI
> Heck, you can even get it in 'rural idylls' when a
> tractor or combine is switched on: many's the time
> I have heard a generator in an engine being fired
> up thru the speaker/headphones[/si
> ze] in the middle of nowhere with just 'birds'
> singing and nowt else!

What you are saying makes a lot of sense because I feel like I do a lot better at finding silver coins in the very early morning hours than I do later on in the day. I wish someone would invent a portable EMI meter that would tell you the type and strength of the EMI at a site so you'd know which detector would work best at that particular site.

tabman

There was an article in an old treasure mag from the 1980s or early 90s that mentioned all the variables of metal detecting. An experiment was done using the same three metal detectors on the same (marked off) piece of land....same person. This was done everyday for a week. Of course it wasnt about how many finds one dug......as you'd think one would find the most on the first day (not so). It had to do with the machines stability, depth, ease of ground-balance, ect.....They recorded the ground conditions and barometric pressure......overall weather. Some of the days the machines were very noisy and difficult to GB. Also some days one had to Ground Balance many times. Lots of variables



Edited 1 time(s). Last edit at 05/04/2019 10:25PM by Arkansas.

" I wish someone would invent a portable EMI meter that would tell you the type and strength of the EMI at a site so you'd know which detector would work best at that particular site."

I started the thread asking if there was one.

Heck, during my daily tests on New Products, with Minelab I was even testing the 'PH' content of the soils and was reporting all that extra info back to the powers!!!

I found this under "How to measure dirty electricity" at emfanylisis.com:

My favorite simple EMI detector is a basic AM radio. You turn the AM dial all the way to the left (500 KHz) and right (2 MHz) and the radio will show you a difference in static based on changes in the electromagnetic environment. This is especially good for detecting dirty electricity in a home. I do this at the circuit panel to find sources. You can always contact me to learn how to do this. I partly demonstrate this in this video.

Picketwire Wrote:
-------------------------------------------------------
> I found this under "How to measure dirty electrici
> ty" at emfanylisis.com:
>
> My favorite simple EMI detector is a basic AM radi
> o. You turn the AM dial all the way to the left (5
> 00 KHz) and right (2 MHz) and the radio will show
> you a difference in static based on changes in the
> electromagnetic environment. This is especially go
> od for detecting dirty electricity in a home. I do
> this at the circuit panel to find sources. You can
> always contact me to learn how to do this. I part
> ly demonstrate this in this video.

That will only show one type of EMI. The digital EMI (cell phone towers, wifi, bluetooth) wont be picked up but can still interfere with detectors.

======================================================

You can see my videos here: [www.youtube.com]
My blog is here: [thesilverfiend.com]

======================================================

...Why I love this Forum - some great Q's are fielded!

Here is another thing to consider... ferrite core bead clamps. Some data cables have them pre-installed. You can buy them in all different sizes. They act as EMI blockers. I have never seen anyone using them on a metal detector. I have heard they wont help, but they wont hurt either.

wondering what others have thought about their use on detector coil cables.

======================================================

You can see my videos here: [www.youtube.com]
My blog is here: [thesilverfiend.com]

======================================================

What about an EMF meter ?....measures electo-magnetic fields (microwaves produce mG). Curiously an EMF meter is a tool used by ghost hunters.