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Pulse induction and push button controls

Turtleman

New member
Forgive me if this appears to be a stupid question but it seems that most modern vlf detectors such as fisher F75 minelab explorers and a lot of others use push button controls to adjust things like sensitivity, ground balance, threshold were they can fine tune the detector a lot more precisely. Now in PI unit like TDI, Gp4500 and others
they still use old style knobs for most of there controls for adjusting grd bal, sat speed. Is this just the nature of pulse in that it doesn't lend itself to this type of control or is.there another reason. It also seems to me in the field that the push button controls are a lot less likely so get bumped out of adjustment. i'm quiet excited about the
advancements that appear to be happening in discriminating pulse induction detectors, it just seems that when i look at them they resemble vlf detectors of the 70's.
Forgive me if my post is a little garbled, but i'm in the middle of a very intense field test of a new single malt scotch. !!!! IT'S A SMASHING SUCCESS!!!

Everybody have a safe and GREAT HOLIDAY SEASON!!!

If yu ain't failin Yu ain't tryin!!!!
 
Hi Turtleman,

Adding features such as pushbuttons to make adjustments may seem convenient to the user, but such a feature may not add any real advantage. In fact, in some cases may be a disadvantage, especially when dealing with PI's.

One should realize that a PI is not a VLF and does not act like a VLF, especially when dealing with low level signals and noise. A VLF can be quite selective in frequency, but a PI has to be broadband if it is going to be sensitive to all sizes and types of metals. This broadband design concept makes such a design very sensitive to any form of noise generator including that of a microprocessor. So, to convert to a digital design can easily introduce unwanted noise, with little advantage to offset this disadvantage. This becomes even more apparent when trying to make a very sensitive detector.

The second issue of importance is time to design such features. Generally speaking, the PI market is quite small by itself, so it is not that practical to try to develop a digital design into such a limited market. Only larger companies that are already using such designs have the time and resources to try to develop such features.

What many people do not realize is going to digital in many cases is not for convenience, but is used as a means of reducing costs by reducing component count. Are there areas such as using digital to reduce costs on a PI? Yes, of course, providing it can be done without introducing excessive noise. Thus, using a microprocessor just might introduce a lot of extra engineering time to minimize possible noise problems. This will ultimately result in increase costs of the detector. So, then one has to decide if the increase cost is worth the convenience and determine whether the customers will agree.

Right now, extra care has to be used to avoid having even the power supplies introduce noise on a PI. So, in many if not most cases, even the secondary features such as the power supplies are synchronized to minimize any possible noise introduction. This is much more difficult to do with microprocessors. Instead, additional care has to be used to both shield and filter the possible noise from such a device.

One of the bigger complaints right now by owners moving from a VLF to a PI is the extra threshold noise factor and this occurs even without the use of microprocessors. So, there is this concern even today about the extra threshold noise or noise susceptibility that PI's have already. Introduce even more of the same unwanted noise and it could be enough to turn people away from the PI technology. So, care has to be used when such technology is introduced.

The issue really isn't whether to introduce such features but rather if adding such a feature can be done cheaply and without adding more problems. So, what may seem minor to a user, can be a major concern for a manufacturer.

Reg
 
Hi Reg

Thanks for the response. I always read your post's with great interest.
In my mind I always thought that digital or microprocessors would have introduced less noise, but obviously not the case.
How are your mod's working out on your TDI, and do you see Whites making any changes to that unit in the next year or so. Have you heard of any of the other manufacturers coming out with a PI unit to rival the TDI in the same price range? I wonder if First Texas or Garrett have anything in the works. Even though as you said it's a pretty small market, a discriminating pulse induction unit could really change that especially if they could get the price down to that 1000.00 to 1200.00 range. I know for myself being mainly a coin hunter,beach hunter and a wantaby nugget hunter the TDI has a lot of appeal.


Turtleman
 
Hi Turtleman,

Digital circuits switch extremely fast and this fast switching creates a lot of noise. In fact, most of the IC sockets designed to be used with digital design have capacitors built in to minimize this noise problem.

As for my mods to the TDI, I haven't done that much as of yet. I have reduced the delay and changed some caps, but that is all. These changes enhance signals to small gold, which what I was aiming for. I do need to tackle some of the noise issues next. I am also considering adding a second GB control and the ability to quickly change between the two, maybe with a push button. This would allow for a quick test of targets. My initial idea is to operate at regular GB and make a quick check to eliminate nails. This would give more sensitivity while searching. Now I have to manually change the GB control each time a new suspected good target is found. In many areas, this isn't a big deal since good targets are normally few and far between, but could be a problem in certain areas where there are excessive nails.

I have no idea just what the other manufacturers you mentioned are going to do. My guess is they will wait and see how well the TDI is received, especially with the economy the way it is. So, I wouldn't be looking for anything new for a while and this includes any major mods to the Whites TDI.

Reg
 
Hi Reg

One of the reasons for my original question was due to the fact that every time you want to check a target you had to reach over and adjust the gb. For prospecting may not be a big issue, but my main application would be coin and beach hunting. It would be great if you could have like a default setting with a push of a button instead of having to reach across. I usually have something in my left had when I hunt so would be a little bit of a pain, unless of coarse i was pulling out silver coins.
I saw on one of the other forums were Garrett has an industrial PI mine sweep detector. I wonder if it has any possibilities in the hobby arena. Time will tell. Maybe that Pulse devil will resurface, AGAIN!!!

Have a good Xmas

Turtleman

P.S Reg. All i had to do is look to the next post on the forum and someone has posted a link to that Garrett unit, which I'm sure you've already seen. Put the TDI in that format and it's the next generation of detectors. It's a beautiful thing.
 
Hi Turtleman,

If you looked closely at the new Garrett PI, you probably noticed it used 8 AA batteries which would imply it is a low powered PI. On the plus side, it should make the unit lighter and easier to reduce the delay.

Now, as for your idea of a default GB setting, my plan is to have two separate GB controls and simply switch between them using a pushbutton or possibly a simple toggle switch. This is not that difficult to do and doesn't require any complex circuitry. Right now, I am doing what you are doing and that is when a suspected object is detected, I do adjust the GB to see if it is a nail or not. Fortunately, in the park I hunt, the older deeper coins are few and far between, as are the nails, so this type of testing of a suspected object doesn't get that tiring. I am like you and want a much easier way of making the test, so when time permits, I will add the extra GB control and the necessary circuitry.

Reg
 
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