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Coin on Edge
- Thread starter below2doe
- Start date
TheMarshall
New member
below2doe said:Hi Guys,
How do you all go with coins on edge. I have the v3 and only can get a coin on edge one way.
Regards Below2Doe.
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[attachment 166285 Sweep.jpg]
This is what you should be aware of.
You can normally only detect a coin if your sweep is transverse, rather than 'in line', depending on distance or depth.
In air tests will produce varied responses from any direction, again there are other factors such as the coin's thickness.
Even the shape of the coil's 'pattern' can cause variations to what is implied in the rough drawing.
A smaller diameter coil should hit from either direction.
Are you using a steel clad coin, and experiencing some degree of 'rejection'???????
Hope that makes sense......same with any detector....
TheMarshall
The Beep Goes On
New member
All detectors I have tested have problems when the sweep is parallel to the coin and do best when perpendicular to the coin. All angles inbetween will give signals that may need to be more fully investigated (by circling the target).
gilfordberry
New member
It isn't rocket science, guys. The electrons in the target are excited by the RF energy sent out by your transmit coil. They tend to spin in a circle in the target, producing their own radio signal which is what your receive coil is waiting to "see". That signal is greatest perpendicular to the plane of the spin. That means the greatest signal produced is outward from the "head" and the "tail" of the coin. Smallest signal is sideways from the face and tail of the coin. Thus a coin parallel to your detector produces greatest signal return; one on end produces least signal; like turning your TV antenna 90 degrees from best reception. If you get a "coin on edge" type signal, you can usually tilt your coil a bit to better ID your target. Also helps to pinpoint it. Gil
: TheMarshall
New member
gilfordberry said:
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Hi Gill....Good post, but I suggest the use of 'RF' is not quite applicable. Metal detecting is about 'transformer action', and 'near field' stuff.
Your opening comment triggered recollections of how the principles involved in the subject matter were indeed relateable to
gilfordberry
New member
I think your understanding of near field effect would definitely be appropriate for a pulse induction machine, where the field collapse time is lengthened (and is thus detectable) by a change in inductance of the coil caused by metal within the collapsing field. VLF machines are RF devices by definition, so I'll stand by my previous statement.
Larry (IL)
Well-known member
Although magnetic propulsion has very little to do with metal detecting, a good example to use is the roller coaster rides at the mega amusement parks where one is "shot" off of the starting line magnetically, high speed rail service is another.
Most metal detectors are RF devices. The operating frequencies of 2.5, 7.5 and 22.5 of the V fall into the VLF (Very Low Frequency) range of the Radio Spectrum.
Most metal detectors are RF devices. The operating frequencies of 2.5, 7.5 and 22.5 of the V fall into the VLF (Very Low Frequency) range of the Radio Spectrum.
TheMarshall
New member
A little knowledge is a dangerous thing.
Meaning
A small amount of knowledge can cause people to think they are more expert than they really are.
Origin
First used by Alexander Pope (1688 - 1744) in An Essay on Criticism, 1709:
"A little learning is a dangerous thing; drink deep, or taste not the Pierian spring: there shallow draughts intoxicate the brain, and drinking largely sobers us again.
TheMarshall
Meaning
A small amount of knowledge can cause people to think they are more expert than they really are.
Origin
First used by Alexander Pope (1688 - 1744) in An Essay on Criticism, 1709:
"A little learning is a dangerous thing; drink deep, or taste not the Pierian spring: there shallow draughts intoxicate the brain, and drinking largely sobers us again.
*********************************
TheMarshall
Larry (IL)
Well-known member
TheMarshall
New member
Ray, I couldn't agree more with your sentiment.....but with the added proviso!
I say that knowledge comes from both learning and working, but wisdom come from the time spent in applying both.
So if wisdom is the qualification, then may I solicit your comments on the subject involved?
It originally was regarding a coin on edge and the V3's response.
We all generally generally agreed on the causes, so that led to other side issues.
The principle one being Gill's definition of the modern metal detector as being an RF device.
I differed, and explained that the modern Induction Balanced detector is basically a conductivity meter working on the principle of an air cored transformer, and 'near field effects'.
Larry and Gill still contend that it is indeed a Radio Frequency device.
Neither give a proper account of why for instance, the Spectra can be called an RF device.
Can I call on your wisdom, and wide experience of the modern Induction Balanced detector, to assist readers?
Maybe rcassio (Whom I understand has taught electronics ) can join the debate?
Looking forward to any genuine input..........TheMarshall
I say that knowledge comes from both learning and working, but wisdom come from the time spent in applying both.
So if wisdom is the qualification, then may I solicit your comments on the subject involved?
It originally was regarding a coin on edge and the V3's response.
We all generally generally agreed on the causes, so that led to other side issues.
The principle one being Gill's definition of the modern metal detector as being an RF device.
I differed, and explained that the modern Induction Balanced detector is basically a conductivity meter working on the principle of an air cored transformer, and 'near field effects'.
Larry and Gill still contend that it is indeed a Radio Frequency device.
Neither give a proper account of why for instance, the Spectra can be called an RF device.
Can I call on your wisdom, and wide experience of the modern Induction Balanced detector, to assist readers?
Maybe rcassio (Whom I understand has taught electronics ) can join the debate?
Looking forward to any genuine input..........TheMarshall
tony (Orlando FL)
New member
Hello Marshall.
I agree that the signal output principle is more in line with a magnetic tape head inducing a magnetic field into the soil than it is radio signal transission YET, however, when something oscillates and develops a field about itself AND can be also picked up by an adjacent metal detector some distance away, the means at which it does this is considered RF. If a radio receiver were tuned to the same freq as the xmit freq of a metal detector it would receive the xmit signal as well, therefor its output is RF. The radio is an RF device which also emits a frequency of its own in order to receive same freq it is interested in receiving.
The reason I feel comfortable in agreeing that the output or coil is more magnetic tape head like than radio antenna like is because the engineering of the search coil currently does not use a reflector or a director element to focus the coil energy into the soil. The output is as you suggest, via a transformer like effect.
What do you think?
Tony
I agree that the signal output principle is more in line with a magnetic tape head inducing a magnetic field into the soil than it is radio signal transission YET, however, when something oscillates and develops a field about itself AND can be also picked up by an adjacent metal detector some distance away, the means at which it does this is considered RF. If a radio receiver were tuned to the same freq as the xmit freq of a metal detector it would receive the xmit signal as well, therefor its output is RF. The radio is an RF device which also emits a frequency of its own in order to receive same freq it is interested in receiving.
The reason I feel comfortable in agreeing that the output or coil is more magnetic tape head like than radio antenna like is because the engineering of the search coil currently does not use a reflector or a director element to focus the coil energy into the soil. The output is as you suggest, via a transformer like effect.
What do you think?
Tony
Larry (IL)
Well-known member
I think we are drifting off topic and it is partly my fault. ........Coin on edge..............