field test unit no 001 "model T"

[Aziz]

...
One key aspect is that it bypasses the techniques currently patented by a well known oz company who seem to want to own all the PI ip. ..and makes it hard for us little guys to come up with non infringing technique.
...
Paul.

Yep, I have the same impression of that company. But one guy seems to want to own even physical laws as well.


Looking forward to your invention.

Aziz

[moodz]

Paul,

Is this something you've built in real hardware or is only sims so far?

- Carl

Carl, I made up multiple bench top versions letting plenty of smoke out along the way with only limited real tests because a fair bit of time was spent writing up the idea for the patent apps. however the two key discoveries ...new damping method and a servo to auto regulate are definitely hardware verified.
This invention is based around new behavior apparently not previously discovered in PI technology and describes a system for exploiting it. It is not some arrangement of special parts and though relatively simple ..can be done in analogue or digital ...it does appear to be a new technique and will have benefits especially for monocoils. I don't think it will double the depth LOL. But it will have benefits for earlier sampling, signal to noise, easier ground balance, lower power consumption, wide tolerance to variations in coils and probably more as well. One key aspect is that it bypasses the techniques currently patented by a well known oz company who seem to want to own all the PI ip. ..and makes it hard for us little guys to come up with non infringing technique.
The sims merely provide a means to explore the dynamics of the system and try to understand why it works as well as it does.
We are currently working towards building a prototype based on an existing high performance design. ... However this is new territory and I also shortly expect to add descrim to the list of claims. ..though this has been observed but not quantified yet.

Paul.

[Davor]

5% improvement is not bad at all

[straton]

It sounds good to me...And if it is user, real time controlled, it will improve sensitivity in certain areas. I first heard about impedance matching in high school, from my father. Was too young to understand its implications. In order to get the most energy transfer from source to load, there must be an impedance "match". This is standard 101 course in electrical eng. The better the match, the better the energy transfer. BTW, I am working too on an active damping circuit to get better sensitivity. So far, I have only seen an improvement of 5% to depth range. Hope yours is a lot more.

[Carl-NC]

.... the good news is that we have made major progress in developing a new topology PI front end that does not use damping resistors. ( actually no damping resistance at all )

Paul,

Is this something you've built in real hardware or is only sims so far?

- Carl

[Davor]

I'd say that having heavily damped coil during initial stage, and then relaxing it to see low impedance would squeeze the most juice out of the targets. It would shorten the initial stage, and widen the sampling stage, so that's good. In a way a simple inverting amp does that - as soon as it drops from saturation the effective series resistance drops to one half of what is written on the resistor.

My view of the PI damping is that it is transformed to the targets as well, so all the targets will under such conditions appear more resistive, which in turn ruins discrimination.

[straton]

I never talked about amp noise except in the case of the servo loop, to justify my reasoning. I talked about other parameters that can be of importance to high gains. It is not my problem that some members like to get off the subject.
About your damping circuit, hope it works as you said, too bad you can't publish it, but may I ask why this will improve noise. Since it is damping the coil, it some has a resistance/reactance and it has inherent noise. The only way that I can see, to improve sensitivity in certain situations only, if it is dynamic in nature and over/under damps the coil at specific times.

[WM6]

.... the good news is that we have made major progress in developing a new topology PI front end that does not use damping resistors. ( actually no damping resistance at all )

Really good news! Go ahead moodz!

[moodz]

...anyway back to the main thread.

The amp discussion is interesting .. however it seems to hijack nearly every PI thread .... my opinion is that when there is functional PI design then the amplifier discussion will become relevant ... however without a PI circuit to make comparisons and tests on the discussion is pretty much a waste of time ... EMI from the coil will probably be 20 db above the amp noise floor anyway. LOL.

The VLF guys dont spend all thier time arguing about amplifiers.

...in the mean time while you guys have been waxing lyrical about amplifier development I have been working on the front end ...

.... the good news is that we have made major progress in developing a new topology PI front end that does not use damping resistors. ( actually no damping resistance at all )

A new control circuit perfectly damps the coil at all times utilising a new patent pending technique. It also surpasses all previous art in noise and the invention works on monocoils, DDs, ground loops and differential coils.

.... the bad news is we cant release it ( yet ) to prevent patent leaches from ripping the idea off ... we have had to apply for our own patents to protect the idea.

To give you an idea the first picture below is the response of a 300uH coil with a 200 microsecond Transmit pulse 3.2 amp peak coil current and damped in 5 microseconds ... with NO damping resistor ( the new control circuit manages this bit ).

In the second picture the control circuit magnetic factor is backed off to allow the coil to ring slightly ( remembering that there is still no damping resistor ) ... If you sampled a standard coil at this point in time with NO damping resistor the ringing would be in the order of hundreds of volts .

Because there is no damping resistor ... target sensitivity is greatly increased.
Sampling commences at 5 microseconds.

[straton]

Are you reading the posts? I think enough was said!

[sido]

Please explain what flaws..."I gave advice and my opinion about some of its "flaws"

Ok. understood

Regards Sid

[straton]

I don't see any design flaws because I have not! built this machine but at the same time I can pretty much "see" its capabilities and where this is heading. I gave advice and my opinion about some of its "flaws" and mentioned info that the datasheet does not have! It took me plenty of hours, for example, to do the set-up for the temp. drift. It's free info.

[sido]

Until i see proven design flaws, i am open to Moodz use of the THAT Ic. Looks interesting and I am all for it until proven otherwise.

Cheers Sido

[straton]

Thanks for the advice but my "THAT IC" testing period, is over. Yes,I have designed my own pre amp, with excellent results but it was a bit tricky and time consuming- not to mention the high cost of buying all precision components...have to congratulate you all for the time, effort and info you're given to all.

[Davor]

So why don't you build your own CFIA with discrete transistors and op amps? Unlike a THAT configuration that has unbal output you could make it double balanced, just like the THAT's inspiration - Cohen preamp had. You want to use it for AD converter, and those are happiest with balanced signal ... even a bit of bias would not bother you any more

Alternatively if you insist on THAT solutions, try THAT1570. It is basically 1510 without the output differential amp. The only downside is 0dB common mode gain (no cross-coupled diff amps to enhance CMMR), but for supplying AD converter WITH a balanced input - that's just fine.