UKD2User Posted October 30, 2023 Share Posted October 30, 2023 On 10/29/2023 at 7:52 PM, Geotech said: "All single frequency, multifrequency, and PI designs use accumulation. " I'd be fascinated to know how you know this, given the level of encryption protecting most embedded code in modern detectors - have you seen the source code or reverse-engineered one/several? Yes, I'm sure that target responses at multiple frequencies are compared/correlated in various ways, but 'accumulation' (if it means anything very much) suggests simple addition. We know that the D2 , for example, uses more than one kind of addition and/or subtraction in processing the return signal - there are almost certainly other transformations going on. The great beauty of processing signals digitally is that you can do all sorts of things with them - in the time domain and/or the frequency domain. Link to comment Share on other sites More sharing options...
Popular Post Geotech Posted October 30, 2023 Popular Post Share Posted October 30, 2023 12 hours ago, Digalicious said: Around the same time, I discovered that SMF modes have a primary frequency. For example, the Legend's M1 primary frequency is around 15 khz. I would be in high EMI using M1 and the noise was intense, yet switching to the SF of 15 khz, caused most of the noise to disappear. That's when I realized that SMF is inherently more open to EMI than SF, despite SMF modes having a primary frequency. When I asked about that, an engineer either said it's because the frequencies and their associated EMI gets "accumulated", or he might have said "they get added together along with the EMI". I can't remember the exact term he used, but it was either "accumulated" or "added together". I'll try and find that post. Metal detectors typically use "integration" as a way to improve SNR. It's basically averaging which is a form of accumulation. It can be done in analog or digital. With MF there have been two broad approaches to processing the multiple frequencies. One way is to treat each frequency as a separate single frequency metal detector. That is, each frequency channel is individually ground balanced and individually gives a target response. The results from each channel can then be compared/correlated to determine what the target is. This is what the DFX & V3 do. We'll call this "channelized" processing. Another way is to combine certain signals from each channel to create "composite" signals. One composite signal is typically the ground balance signal, another the salt balance signal, and target information is extracted from the composite signals. The Fisher CZ series uses this method, as do BBS/FBS. Composite processing tends to offer only a single VDI and a single graphable result, whereas with channelized processing you can get multiple graphs and multiple VDIs. This is why the V3 can give you all 3 spectrums. With channelized processing you can treat each channel as a single narrow-band detector and tightly filter it. With composite processing, once the composite signals have been created they now have a blend of frequencies with noise mixed from different bands and you've got what you've got. It's possible that this is what is going on in the newer all-digital MF designs. It would be interesting to see if, say, a DFX or V3 struggle as much. However, another factor is that designs seem to continuously push up gain and sensitivity so maybe a DFX would be quieter but also not go nearly as deep. 3 hours ago, UKD2User said: I'd be fascinated to know how you know this, given the level of encryption protecting most embedded code in modern detectors - have you seen the source code or reverse-engineered one/several? I design metal detectors for a living. No, I don't have any competitor's code but I can deduce some things from how the detector operates. I also look at competitor's patents which are often revealing. 8 2 Link to comment Share on other sites More sharing options...
phrunt Posted October 30, 2023 Share Posted October 30, 2023 4 hours ago, UKD2User said: I'd be fascinated to know how you know this, given the level of encryption protecting most embedded code in modern detectors - have you seen the source code or reverse-engineered one/several? He even wrote the book on it ? 5 2 Link to comment Share on other sites More sharing options...
F350Platinum Posted October 30, 2023 Share Posted October 30, 2023 I'll just leave this here... ? Thanks, Geotech. I'm a relative noob myself, but this forum is loaded with so much experience I just expound wild theories and get my butt kicked. ? It's all good. 2 Link to comment Share on other sites More sharing options...
Chase Goldman Posted October 31, 2023 Share Posted October 31, 2023 8 hours ago, phrunt said: He even wrote the book on it ? Yep. I own it and read it. When Carl (Geotech) pops in here to share his technical wisdom on detectors, I just read and absorb the nuggets and thank him for sharing. He's forgotten more than I'll ever know. As a trained engineer I can somewhat understand and explain the technical concepts but I am not a designer like Carl who can make these concepts come alive in your hands. 7 Link to comment Share on other sites More sharing options...
iron_buzz Posted October 31, 2023 Share Posted October 31, 2023 10 hours ago, Chase Goldman said: Yep. I own it and read it. When Carl (Geotech) pops in here to share his technical wisdom on detectors, I just read and absorb the nuggets and thank him for sharing. He's forgotten more than I'll ever know. As a trained engineer I can somewhat understand and explain the technical concepts but I am not a designer like Carl who can make these concepts come alive in your hands. I spent far too many years on another MD forum hoping to get that sort of information. The one person that was in that group that gave good information left it some time ago. I'm glad that I recently discovered this group. Looking forward to some more in-depth learning! 2 Link to comment Share on other sites More sharing options...
Chase Goldman Posted October 31, 2023 Share Posted October 31, 2023 2 hours ago, iron_buzz said: I spent far too many years on another MD forum hoping to get that sort of information. The one person that was in that group that gave good information left it some time ago. I'm glad that I recently discovered this group. Looking forward to some more in-depth learning! Maybe they ended up over here. ? 2 Link to comment Share on other sites More sharing options...
Digalicious Posted October 31, 2023 Share Posted October 31, 2023 3 hours ago, iron_buzz said: I spent far too many years on another MD forum hoping to get that sort of information. The one person that was in that group that gave good information left it some time ago. I'm glad that I recently discovered this group. Looking forward to some more in-depth learning! That's why I joined this forum. I still participate in another forum, but not so much anymore. I rarely even read or post on the Facebook detecting pages anymore. The other forum mainly seems to be about finds. I wanted a forum that is mainly based in technical aspects of metal detectors, and when it comes to that, this forum delivers ? 3 Link to comment Share on other sites More sharing options...
CPT_GhostLight Posted October 31, 2023 Author Share Posted October 31, 2023 That's a big "Me Too!" I really enjoy seeing all the wonderful stuff detectorists find, but in my quest for detecting and detector knowledge I found the DP forum and quickly discovered that when you jump into such a huge pool of real knowledge, you can't help but soak some of that in. Big Thanks to @Steve Herschbach for creating this place and to all the fine folks who inhabit it! 4 1 Link to comment Share on other sites More sharing options...
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