Bruce Candy Technical Paper - GPZ 7000 Zero Voltage Transmission (ZVT) Explained

[Steve Herschbach]

Here it is folks. Loaded with tuning tips!

http://www.minelab.com/__files/f/254716/KBA%2024-1%20Basics%20of%20the%20GPZ%207000%20Technology%20Zero%20Voltage%20Transmission%20(ZVT).pdf

"A significant technical achievement of GPZ 7000 ZVT technology was in creating the ultra‐stable transmitted magnetic field during the receive period, to ensure that the large reactive component of the soil signal, X, is not detected, in the same way that it is not detected in PI."

Figure 2 shows a comparison between the ZVT VRM soil signal and the nearest equivalent PI soil VRM signal; both transmitted magnetic signals being bi‐polar, with the same fundamental frequency and same rapid change of magnetic field period. It should be noted that the PI receive period is half that of the ZVT period, because the PI system shown in figure 2 transmits for half the time and receives for the other half of the time, unlike ZVT that transmits and receives simultaneously just about all of the time. The important difference in the VRM signals is that the PI signal decays away substantially faster than the ZVT system. This indicates that the receive signal for PI is less sensitive to longer Time Constant (TC) components compared to shorter TC targets than ZVT, and this is one of the main reasons why ZVT technology is better at detecting large nuggets compared to PI; another main reason being from the double length receive period in ZVT compared to PI for the same fundamental frequency.

[russ]

Awesome, thanks Steve.... I've got it booked marked.

[Steve Herschbach]

This will be sort of the "Holy Grail" of the GPZ 7000 that will be pored over, picked apart, and interpreted for quite some time. There is a lot said that answers many questions and raises others.

[Rick Watkins]

Looks like its almost an electro magnet, that could be handy to clean your ground . Flip a switch then drop your nail in the bucket, you shouldn't need the magnetic rake steve or maybe the magnetic field is actually pushing away the steel like two magnets reversed. Wow. Rick.

[Gold Hound]

Thanks for the paper Steve I now have a better undersanding of how zvt works.

Now all we need is all of the audio settings explained.

[Qld Sandy]

The paper by Bruce Candy is well worth the read and is a must for all those with a GPZ. The section about ground balance is the critical area for mine and there are tips to make this procedure accurate. It appears to me that the GPZ is more like a computer than what we have had in the past, and is a totally different animal than the 5000 and older detectors, hence should be regarded as totally new. That means that we need to disregard a lot of the ways of doing things that we have learned and ground balance procedure is the first base. Pumping the coil is not the best way to ensure an accurate balance especially when there are several factors being charted and adjusted out.

 

It makes me wonder whether the testing that was done just after the release is at all accurate, as it was done with the 5000 and older mindset. I'm not trying to disregard it, but have to ask whether it is relevant in light of this paper. With the limited time I have had with the 7000, I can say that it impresses me more each outing as I have seen what it is capable of, and have many customers that give feedback on it. Cheers.

[Steve Herschbach]

Well people can just go right on testing the GPZ vs GPX and trying to prove whether the GPZ is any better or not. Frankly, I have moved on in that regard. As JP says at http://www.detectorprospector.com/forum/topic/748-the-subject-of-the-gpz-7000/

"The GPZ 7000 is what it is, you can either believe or not believe. I believe!!!"

[russ]

The auto ground balance/tracking on the GPZ reminds me of the ECU on the newer cars, or not? 

 

The ECU "learns" about your engine as you drive the car. The "learning" is actually a process that the ECU uses to track the tolerance changes of the sensors and actuators on the engine. 

The ECU is always tracking the engine's sensors and actuators. Resetting the ECU does not cause the ECU to learn engine changes any faster. The ECU is always tracking the gradual changes in the engine sensors and actuators. The ECU never gets satisfied with a setting, and is always updating the trim values. It will discover whatever change you made to your engine and make the appropriate changes. In fact, unplugging the ECU will most likely increase the learning curve of the new part.

[Qld Sandy]

Russ, That's probably a good analogy.

The first of the Holden Commodore engines had a computer with a "Block Learn Memory", which tracked the sensors and actually would substitute a value for one that went missing or out of range. It would also learn and update the fuel curve for engines that were worn or had a lot of milage.

 

I wonder if the GPZ does a similar thing?

[russ]

The paper by Bruce Candy is well worth the read and is a must for all those with a GPZ. The section about ground balance is the critical area for mine and there are tips to make this procedure accurate. It appears to me that the GPZ is more like a computer than what we have had in the past, and is a totally different animal than the 5000 and older detectors, hence should be regarded as totally new. That means that we need to disregard a lot of the ways of doing things that we have learned and ground balance procedure is the first base. Pumping the coil is not the best way to ensure an accurate balance especially when there are several factors being charted and adjusted out.

 

Qld Sandy, between reading your post about the GPZ having more like a computer doing the ground balancing and looking at that beautiful car in your avatar got my wheels turning.