Interior and diagram of the Garrett ACE 250 metal detector

There is a saying: "Ours have been there."
And perhaps even the owner, which he probably won't admit to.

R3 pulls up the gate of the P-MOSFET to the source in the power circuit. There is still some SD_U14 going to this gate, perhaps this is connected to the complementary output.
Error or sloppy assembly or someone has been messing around with the power supply.

To me that massive drop of tin looks like an attempt to make a bridge. I know from experience that if the distances are a bit bigger, it's not easy.

Using too high a temperature when soldering can end up like this, so it's worth experimenting at an electro-smashing shop first and breaking down the pads/elements there to avoid spoiling the equipment for repair. Flux is also essential.

p.kaczmarek2 wrote:

that's why it's worth experimenting at an electro-smashing shop first and breaking down the pads/elements there to avoid spoiling the equipment for repair. Flux is also essential.

Exactly on the example of my case well, unfortunately at the beginning I also damaged something and not just one [I mean the encroachment of SMD technology and these multilayer prints and still flooded with black resin ] it was a novelty for me mentioning here the microscope and even when I connect the inspection camera / magnification at max. / it is still a problem, you look at the screen of the computer and the hands have to coordinate, except that you are not looking at a particular plate, and even here there is the A after getting on the Hot-a , suction cups, braid, etc. this is where the motor coordination comes into play and I admit more than once I have blown off some mini resistor or transistor.
And as for this model of detector a friend has I think an identical one but unfortunately it's under warranty, no option to make him break the seal.

And I'll add, he wanted to check it out and we started these So called piku piku he found me two coins I don't know how to clean them we shared, I have one to the eye perfect only terribly dirty and here the restorer comes into play, because hardly legible they may be worth something or practically zero value [kopiejka ] I know, he made a paper for searching with the detector, and also the shell probably just the price of brass.

I've never seen a detector inside before.
Although there are no ,,black glutes".
Thanks for the large number of photos and the diagram.

#6 for most pix you need a permit.
Worse if you find a bum bum.

Hello, I have dealt and still deal with detectorists, I have even written a little about it, even writing my master's thesis. I have even written a little about it, even writing my master's thesis. I have also dabbled in it as an amateur when I had the time.

First of all, I have to constructively deny the thing, which for a skilled electronics technician bites in the eye .

Don't listen to YT-salesmen, just specific technical channels, gaining knowledge.

No metal detector measures and graphically indicates the conductivity of metals [S/m] - because some on the internets tell you such things.



It is impossible due to the fact that we do not directly know >> the shape, dimension, cross-sectional area, and resistance of the detected object.

Who will assess this underground and how ? ;]


Plus a theoretical and practical simple comparative example,


A simple example - silver is a very good conductor.
Check the reaction of the detector to a large 925 sterling silver ring,
check the reaction to a very thin chain of the same sample or a very thin small coin. In theory, apart from the size of the object, the metal alloy is identical, so the result should be similar (because a very good guide), and it won't be.
And compare it (relative to the chain) with some copper object, which should have a lower result no because it is a worse conductor, and it will turn out to be, for example, higher.

The detector indicates a certain value averaged and calculated according to the adopted algorithm - in short, some ratio of maximum values of vectors resulting from a certain signal received from the detection probe (generally this signal is generated into two components X and Y)


X In-phase (in-phase) Mainly resistivity, conductivity How much current it can let through - e.g. copper, silver give a strong signal in X

Y Quadrature (quadrature, 90° offset) Mainly reactivity, i.e. inductance and capacitance Whether the metal is ferromagnetic or not - e.g. iron reacts strongly in Y

Conductive metals (e.g. copper, silver)

- They give a strong signal in X (in phase) because they conduct well - large eddy current → strong response.
- The Y signal is low because they have no magnetic properties.

Magnetic metals (e.g. iron)
- They give a large signal in Y (quadrature) - the detector "sees" strong inductance (the material delays the signal response).
- The X signal is weak because the conductivity is lower.




And now yes: the calculated value (actually the phase shift of the base signal) will be characterised to some extent (what I have already described above) by the fact that we are able to distinguish between metal alloys because their el, physical properties will affect the phase shift - higher for paramagnetics, lower for ferromagnetics.

This happens through the induced electromagnetic field in the conductor (eddy currents), which are created by the transmitter's excitation of the detection probe.

This field generates a secondary electromagnetic field generated in the receiving section of the detection probe.

The probe is aligned, it has some sort of minimum balance signal (system balance).

The signal generated will have an amplitude that depends on the size of the object and its depth in the ground, and the phase shift will depend on the electrical properties of the object, its shape, size, angle of inclination, depth, thickness, soil, moisture content and more.

This shifted, induced signal is compared to the transmitter's reference signal - it is relative to this signal that it will be shifted in phase.

Generally, the signal is then demodulated in the electronics into two components corresponding to resistive, conductive and reactive values.

There is also the land component (but that is a separate topic).

These signals pass through bandpass filters and are then analysed (analogue or digital) - a ratio calculated, for example, or according to some other algorithm.

fi = arc.tan(y/x)

This will ultimately be the determinant of the angle of deflection of the resultant vector, which can then be calibrated and described graphically, audibly, numerically - e.g. -95 to +95.


The resulting analogue signal is also verified at the end of the detection system, e.g. by a pair of comparators which, against a separate discrimination module (analogue detectors), check whether to generate sound or to reject the signal from the detected object - discriminate.

Digitally, it's similar, but it tends to process the entire spectrum on the fly and simply responds to specific parameters set in some kind of pattern table.

So yes - better materials (conductors) will cause the signal to tend towards maximum vector bias, worse ones in the opposite direction.

But still, as I mentioned, many other factors will influence the definitive identification.

Because the fact that something beats e.g. at VDI = 90 (e.g. a silver ring , a large copper coin) does not classify that we are always dealing in the ground only with material of the "better conductor" classification.
This is because two materials, silver and copper, with obviously physically different conductivity, fall into the same number, but the VDI is definitely influenced by other factors, so that in theory a material with inferior physical electrical properties is on a par with one with better it does not make the slightest sense if we would go back to the fact that the detector calculates, measures, indicates the conductivity of metals and on this basis classifies into better worse, it is not so simple .





X - answers

- Conductivity σ (S/m) → the higher, the stronger the X signal
- Low resistivity ρ (Ω-m) → i.e. copper, silver, gold
- Slightly dependent on shape and depth

Y - corresponds to

- Magnetic permeability μ → ability to conduct a magnetic field (ferromagnetism)
- High reactance → e.g. with iron (strong delayed response)
- Predominantly non-conductive or weakly conductive metals

This is why the detector is said to present VDI numbers - Visual Discrimination Identification, i.e. the identification of the type of metal object likely to lie in the soil beneath the probe.

And some sort of scale is adopted, e.g. from -90 to +90.
Some range is calibrated for copper, lead, aluminium, silver, foil, iron, objects - caps, nails, specific coins, rings and conventionally assigned to the adopted scale.

Then you can comparatively infer what might be under the probe.

But further it is not measuring the conductivity of a specific object.

An ideal paramagnetic will swing the receiving signal in the +90 direction,
An ideal ferromagnetic will tend to swing in the opposite direction of the -90 scale

VDI is only a guide, it does not give 100%, because there are too many factors influencing the measurement result, and it also depends on the depth of the object.



There are also interesting issues of discrimination, i.e. deliberate omission or exclusion of some objects, and ground, which introduces an "interfering" signal for the electronic detection system and should be compensated so that the resultant signal vector "0" of the unawakened detector does not "escape" on the scale (possible false signals, incorrect indications, excitation), but set at the neutral point - the beginning of the scale..

Because the ground itself can also have conductive , magnetic and other properties, so it physically induces a signal in the receiver coil of the detector and this should be nullified at the outset.


I encourage you to read the articles of the monthly magazine Discoverer on the construction of detector >>> series by Mr Proscan from Gliwice, who is one of the "gurus" when it comes to knowledge of principles and assemblies. He has his own proprietary solutions, but mainly deals with service.
For the more inquisitive, there are several English-language items on detector construction and even home experiments step by step designing simpler circuits for the final device.
(Inside the metal detectors)




A properly repaired detector (above) should additionally be connected and tested complete with a detection probe, which forces the whole transmitter/receiver system. The whole thing should of course preferably be connected to an oscilloscope at the appropriate measuring points and then checked for correct probe compensation, signal generation from the detected object, X/Y channels, ground response, ground imitation and response to various objects etc .

Detectors in general are a very cool and interesting topic.



Greetings!

The ACE 250, nicknamed the canary because of its colour, although classified as an 'entry level' detector is a pretty good piece of equipment and often successfully competes with many more expensive detector models. In my opinion this is due to the fact that the input stage and phase detectors and filters are a simplified version of the once flagship Garrett 2500. Add good software and the detector for $200 (I think it was introduced in 2008 with such a price) turned out to be a market hit. The weak point of this detector is the coil, so independent manufacturers were quick to respond and there is a good selection. I tested the Canary with a 13" coil and was impressed. It certainly won't 'see' a piece of broken 2x2mm silver coin even with a small coil, which better detectors such as the EQ800 can do. It won't fight in salt water either. But a larger coin like a boratin can already "see" and identify it from a comparable but slightly smaller depth. I have been to a few rallies where quite a few people were running around the field with various equipment and in the end it happened that the owners of the canary were in the lead of the "discoverers". Because there are few places where there are pieces of 2x2 mm coins or other hard-to-detect objects. Seawater in our lakes does not occur. Besides, the detector is only a 10-20% chance of success, the rest is the operator, his intuition and certainly some luck. This is of course my opinion based on observation.
I once read a very accurate opinion. 'The detector will not signal the presence of a coin if it is not under the coil'.
I will add from myself- even the best or most expensive one.

I used this model to find ironstone in the field. I didn't find any iron. In the yard I managed to find beer caps. Somewhere in the woods it squeaked hard, but I didn't want to dig for explosive surprises.
In the trials in the courtyard the iron was found, so it's possible I missed them in the search area.
Instead, I found other ironstone lost many years earlier. The searcher indicated roughly the search area. One pass and the detector beeped. With the precipitator at the first spade penetration, the lost item was hit. Rusty, but recovered.
I also have a folding unit, but can't get it together to do the coil holder and electronics. This is how it even works well. I haven't done field trials of the folding unit.

To me, my father once made a toy on a two-frame feta. It was able to detect the bathtub and the fridge in the flat. Some smaller things from a short distance too, but I didn't run around in the fields with it.

The hobby metal detector does a little more than detect 'iron'. In general, it is probably the abundance of coastal or other beaches that has made this equipment so popular. Some of the simpler models are even referred to as 'beach bugs'. During the summer season, people lose a lot of coins and even jewellery on the beaches. You can even find a buried beer can. I don't know how it is today, but in the past you could pull out about 50 zlotys a day and sometimes much better if you found jewellery. Some locals used to earn a lot by digging all season. Back in the day, White's XLT high-end equipment displayed icons that corresponded exactly to American coins. And it worked pretty well, so on the beach the prospector knew with great certainty what he was digging for. In the USA, of course.
The most important feature of the detector is the identification of the type of metal detected and its quality. So that the detector does not mistake a rusty bottle cap for a coin. Many sellers mistakenly call identification discrimination. Discrimination is rejection, so there is no discrimination without identification. Many searchers do not use discrimination anyway, preferring to have the full picture under the coil, besides which, according to some, enabled discrimination spoils the quality of identification.

j570 wrote:

The most important feature of a detector is the identification of the type of metal detected and its quality. So that the detector does not mistake a rusty cap for a coin. Many sellers mistakenly call identification discrimination. Discrimination is rejection so there is no discrimination without identification.

You are wrong, discrimination in the simplest version of the detector allows you to ignore iron in favour of precious metals but without identifying them.
On better detectors you can turn on Notch or selective discrimination and here you get something like identification.

acctr wrote:

In better detectors you can turn on Notch or selective discrimination and here you get something like identification.

.
Have you mate ever seen a modern detector? If not then at least read what AoT_Hunter_PL wrote about identification.

j570 wrote:

The hobby metal detector does a little more than detect 'iron'. Generally, it's probably the abundance of coastal or other beaches that has made this equipment so popular. Some of the simpler models are even referred to as 'beach bugs'. During the summer season, people lose a lot of coins and even jewellery on the beaches. You can even find a buried beer can. I don't know how it is today, but in the past you could pull out about 50 zlotys a day and sometimes much better if you found jewellery. Some locals used to earn a lot by digging all season. Back in the day, White's XLT high-end equipment displayed icons that corresponded exactly to American coins. And it worked pretty well, so on the beach the prospector knew with great certainty what he was digging for. In the USA, of course.
The most important feature of the detector is the identification of the type of metal detected and its quality. So that the detector does not mistake a rusty bottle cap for a coin. Many sellers mistakenly call identification discrimination. Discrimination is rejection, so there is no discrimination without identification. Many searchers do not use discrimination anyway, preferring to have a full picture of the situation under the coil, besides, enabled discrimination, according to some, spoils the quality of identification.

Hi. Not necessarily, since the 1980s-90s detectorists have been and are widely used both amateur and professional for archaeological work, searching for militaria, coloured small objects, and there is also a beach or even underwater faction.

At the moment, the market is being destroyed by 'YT-tube' content. A lot of people, lured, not necessarily passionate, just on the basis of "it's cool, it's trendy, I'm into it too", are searching, destroying this hobby .

And yes, when it comes to beach conquests, there's such competition now that it's not the same as 20 years ago - first come, first served. Walking between the legs of beachgoers or racing who's first to the beach in the evening, that is, at 11pm, 3am, because after all, by 6am it will already be searched.

I personally don't like it, but people whine that it's getting worse because there are more and more people wanting to go.

When it comes to actual good trophies like gold jewellery - compared to the quantity - Poland is hardly a paradise. Such things come out more often in countries where tourism is more developed and more people pass through.

Added after 18 [minutes]:

acctr wrote:

j570 wrote:

The most important feature of a detector is the identification of the type of metal detected and its quality. So that the detector does not mistake a rusty cap for a coin. Many sellers mistakenly call identification discrimination. Discrimination is rejection so there is no discrimination without identification.

You are wrong, discrimination in the simplest version of the detector allows you to ignore iron in favour of precious metals but without identifying them.
In better detectors you can turn on Notch or selective discrimination and here you get something like identification.

You have not understood the message of your colleague above.

For discrimination to work, the electronics circuitry has to correctly try to identify the range within which we can cut off, filter out, isolate a signal from an unwanted target - and against something this has to be compared.
And it is not at all that simple, as ferromagnets - because of the for their properties and their being buried in the ground - can cause electronics to receive a signal that is not necessarily 100% characteristic of such a target, only to be interpreted as 'coloured'.

Because of this, there is no perfect detector - even the better ones can interpret a target's response as a colour signal, and it will be corroded iron (even a Deus XP like this).

So yes, discrimination allows you to exclude a given range of targets or even a specific range, and NOTCH mode is related to it.

Although I personally would separate identification from discrimination.

Because mostly identification is associated with information that the user already gets in the form of sound or graphics.

But the above is, sewn into the detection circuitry of the device - and the values are compared to allow discrimination of unwanted targets, setting some values assigned to a specific range.

Discrimination (and in fact the target response signal) is related not only to the type of metal, but also to the size of the metal, the depth of the target - because you can, after all, exclude aluminium foil from the initial range, but at the very end of the range there will still be a response to large aluminium targets (manners etc).
Simply put, there is some algorithm or implemented functionality [analogue], which deviates some signal (data) at the input, has to process it interpret it and spit something out at the output .


The subject is broader - a book would have to be written here, there are so many things related to it.

Added at 8 [minutes]:

j570 wrote:

acctr wrote:

In the better detectors you can turn on Notch or selective discrimination and here you get something like identification.

It's not like that.
Have you mate ever seen a modern detector? If not then at least read what AoT_Hunter_PL wrote about identification.

Yes, notch is selective discrimination, but it is not an identification option.
It simply allows a smaller area to be cropped out, allowing the response of the target (the undesirable one) to be filtered out, retaining the ability to respond to the entire remaining range.

A colleague was probably referring to the indirect method in single tone analogue detectors, where there were no multitones, just the ability to discriminate by moving the range manually with a dial.

At the minimum setting - let's assume - you detect a target. By turning the discrimination potentiometer, we check at which position the target response is lost, e.g. at a value of 5 (out of 10). And we know from experience that, for example, in this range are medium-sized copper objects, brass objects - and it could be, for example, a Mauser shell.

But rest assured - good analogue detectors also had multitone capabilities, selective discrimination, visual or audio identification options .

AoT_Hunter_PL wrote:

You have not understood your colleague's message above.

j570 wrote:

Discrimination is rejection so there is no discrimination without identification.

The colleague above was clear and this message is clearly wrong.
In simpler analogue detectors with discrimination there is no identification and yet you can successfully use discrimination to avoid digging in vain for a steel cap.
It's like seeing from a distance that there's something on the road that has four paws and it could be a dog, a wild boar or a deer, but the bottom line is that you see it's an animal and not a human - you haven't identified what it is, but you know you won't humanly talk to it .
In general, the term 'discrimination' has a deep-rooted meaning in detectors and stems from pioneering analogue designs. Today we have DSP and despite this further discrimination is used by manufacturers and this is no mistake.