TGSL Tuning & troubleshooting

[johnsmith77]

Only inversion is the same, when grounding LF353 pin 5 or 6, not the phase shift.

[johnsmith77]

Please ignore this on the post 1618338:
"Furthermore i thought more and got decision: LF353 pin 6, or pin 5 is grounded there will be no difference. I bet. There is no mistake and both manuals correct at this point"

And sorry for multiposting.

[der_fisherman]

Interesting question.

I tried LTSpice simulation and attached photos shows my results. They don't match yours exactly. However, I don't know if correct. Did you try with actual circuit?

I can't explain slight phase shift between the cases; maybe due to different impedance of op amp inputs???

These waveforms are of course just the "null" signal, does not show how target signal phase would be affected if at all.

-SB

P.S. I don't trust this yet because I recall trying a similar comparison for dfbowers and did not see difference between his "wet" grass version (vout3) and the TGSL standard (vout1). So I need to doublecheck.

What format is the file ".ASC" is not recognised by my windows PC. Can you post it in an easier, more common format, or give me some tips as to how I can view it? Thanks in advance.
Andy

[simonbaker]

What format is the file ".ASC" is not recognised by my windows PC. Can you post it in an easier, more common format, or give me some tips as to how I can view it? Thanks in advance.
Andy

Hi der_fisherman:

That is an LTSpice simulation file, in case you want to play with the simulation yourself and try different configurations.

LTSpice is free -- if you google it, you should find the download for it.

-SB

[simonbaker]

Not me guv!
This is one of Simon's.

I think he is referring to a mod you once proposed to line up the center frequencies of the two op amp filters, or something like that -- changing the feedback cap on last filter stage.

-SB

[der_fisherman]

Hi der_fisherman:

That is an LTSpice simulation file, in case you want to play with the simulation yourself and try different configurations.

LTSpice is free -- if you google it, you should find the download for it.

-SB

Ah!! That explains it, many thanks.

[johnsmith77]

I solved it. I know why?

It depends on cable connection mode.

Connection "for wet grass" according to ussuall cable connection to coil, changes signal polarity on Tr4, Tr5, drains. Also it changes phase shift by 90 degrees.

Do you agree?

I am interested how is going coil nulling if someone is trying null, having standart cable connection on his TGSL and that someone compares his oscilograms to oscilograms of "wet grass" connection. The second person should think he made coil wrong, then he make another hoping then he will get oscilograms as got the first person, then again again and big trouble.
He can faill

Maybye it was disscused in forum before, but i could not find?

Thanks

Seems now i solved in real.

It happens because i always was scopping when TGSL coils put on boxes (0,5m away from any metal). GEB signal on TR drain positive.
Only few times i scopped on table (some metal around, maybye bolts). GEB signal on TR drain negative.
By this accidence i saw that signals on tr4, tr5 become inverted.

All scillograms i saw on TGSL forum, has GEB signal on TR drain - negative. I make decision they are scoppend with some nearby metals.

Sounds funny maybye Have no other explanation.

[simonbaker]

Seems now i solved in real.

It happens because i always was scopping when TGSL coils put on boxes (0,5m away from any metal). GEB signal on TR drain positive.
Only few times i scopped on table (some metal around, maybye bolts). GEB signal on TR drain negative.
By this accidence i saw that signals on tr4, tr5 become inverted.

All scillograms i saw on TGSL forum, has GEB signal on TR drain - negative. I make decision they are scoppend with some nearby metals.

Sounds funny maybye Have no other explanation.

Good observation, but I don't think that explains all the other waveforms.

Let's try to figure this out. Maybe it's just a simple thing we're looking at differently.

Can you get a dual-trace scope to take very reliable measurements?

Your last graphs were relative to LF353 pin 7, but that is difficult to interpret.

Can you make all the same graphs but relative to TX oscillator? That is where we need to start.

Also note: the signal at TR4 and TR5 Drain is basically the same signal -- any difference (other than DC offset) is probably due to some feedthrough of Gate signal -- don't you think?

Regards, SB

[satdaveuk]

Ivonics TX mod

Hi
anyone done the mod on the TGSL same as IGSL putting a 10k preset and changing a couple of resistors in the TX tank circuit.
At first i thought it a good mod but after setting up with the scope i since notice that the sense pot doesnt work and disc pot no different, disc switch works but takes silver out, tryed variations of adjustment to no availe.
im working with a factory 8" coil round, could that be the difference?
Or maybe ive put a fault on the unit any advise, im still on 14khz, everything sounds like it did, sense on iron is the same as ever.

Thanks in advance
Regards

[johnsmith77]

Good observation, but I don't think that explains all the other waveforms.

Let's try to figure this out. Maybe it's just a simple thing we're looking at differently.

Can you get a dual-trace scope to take very reliable measurements?

Your last graphs were relative to LF353 pin 7, but that is difficult to interpret.

Can you make all the same graphs but relative to TX oscillator? That is where we need to start.

Also note: the signal at TR4 and TR5 Drain is basically the same signal -- any difference (other than DC offset) is probably due to some feedthrough of Gate signal -- don't you think?

Regards, SB

At this moment i can't get dual scope. I measured by sound card scope. I didn't attach pictures, because they looks ugly and are not stable at higher frequencies. But i managed get some info from it.
I measured Tx J1-1 vs LF353 pin 7. Rx signal lags about 17-20 degrees according to Tx signal, phase shift negative.

So my all previously attached graphs will be lagged about 20 degrees according to Tx.
Can we make any decision at this point?

[simonbaker]

At this moment i can't get dual scope. I measured by sound card scope. I didn't attach pictures, because they looks ugly and are not stable at higher frequencies. But i managed get some info from it.
I measured Tx J1-1 vs LF353 pin 7. Rx signal lags about 17-20 degrees according to Tx signal, phase shift negative.

So my all previously attached graphs will be lagged about 20 degrees according to Tx.
Can we make any decision at this point?

As you noted, the RX phase can change easily with nearby metals or changes to coils, noise, etc., so it is difficult to trust any phase measurements relative to RX. Even with TX as reference, I usually need to make measurements many times to be sure I did it correctly.

I also find it difficult to think unless I see actual dual trace comparisons of the waveforms relative to TX signal. Too much mental arithmetic. But if you can show the waveforms relative to TX somehow, we can try to analyze. However I am afraid a sound card scope may not be good enough and may cause phase shifts of its own as well as waveform distortion.

Let me ask first: how do you determine phase with your sound card scope? What is the reference? How does the trigger work?

Regards,

-SB

[johnsmith77]

As you noted, the RX phase can change easily with nearby metals or changes to coils, noise, etc., so it is difficult to trust any phase measurements relative to RX. Even with TX as reference, I usually need to make measurements many times to be sure I did it correctly.

I also find it difficult to think unless I see actual dual trace comparisons of the waveforms relative to TX signal. Too much mental arithmetic. But if you can show the waveforms relative to TX somehow, we can try to analyze. However I am afraid a sound card scope may not be good enough and may cause phase shifts of its own as well as waveform distortion.

Let me ask first: how do you determine phase with your sound card scope? What is the reference? How does the trigger work?

Regards,

-SB

I determine phase shift by this:

Frequency measured by sound card scope frequency meter shows: 14,51 khz.
Tx, Rx signals period for 360 degrees (period) - i see ~ 68us.
Difference between Tx and Rx i see ~ 12us.

So 12us / 68us = 0,176 x 100 = 17,6 %
Phase shift ~17,6%. Negative
In forum oscilograms i see phase shift positive 20 %.

Triger is not very good at higher frequencies of sound diapason . A little sweeping, but not so big as i could not measure.

Positive or negative shift, there is the reason? No double beeps for my coil. Tx 14,51. Rx also should be about 16,1. So?
Did previous scoppers mixed their Tx or Rx start, end connections ?

[simonbaker]

I determine phase shift by this:

Frequency measured by sound card scope frequency meter shows: 14,51 khz.
Tx, Rx signals period for 360 degrees (period) - i see ~ 68us.
Difference between Tx and Rx i see ~ 12us.

So 12us / 68us = 0,176 x 100 = 17,6 %
Phase shift ~17,6%. Negative
In forum oscilograms i see phase shift positive 20 %.

Triger is not very good at higher frequencies of sound diapason . A little sweeping, but not so big as i could not measure.

Positive or negative shift, there is the reason? No double beeps for my coil. Tx 14,51. Rx also should be about 16,1. So?
Did previous scoppers mixed their Tx or Rx start, end connections ?

Is it a dual trace scope? If so, I would appreciate actual pictures with TX signal as top trace. I am never clear with word descriptions.

And could you say again what is the main difference between your signals and other peoples on this forum? I want to make sure I understand.

Regards,

-SB

[Jerry]

johnsmith77: Simon is right, you really need to find a scope so you can look at the relationship of both signals. What you are looking for is a phase shift expressed in degrees of a full cycle (360 degrees), not a percentage of it.

Your method is creative but I dont think it is going to work in this instance.

Jerry

[johnsmith77]

Is it a dual trace scope? If so, I would appreciate actual pictures with TX signal as top trace. I am never clear with word descriptions.

And could you say again what is the main difference between your signals and other peoples on this forum? I want to make sure I understand.

Regards,

-SB

Examples with positive phase shifts (Tx J1-2 vs LF353 pin 7):

a) http://www.geotech1.com/forums/attac...1&d=1261343207

Source: http://www.geotech1.com/forums/showthread.php?t=16122

Timebase: 20us; Phase shift: positive 57 degrees.
[calculated: 12us /76us x 360 ]

b) http://www.geotech1.com/forums/attac...1&d=1192949609

Timebase: 50us; Phase shift: positive 102 degrees. (calculated: 20us / 70us x 360 ]


Source: http://www.geotech1.com/forums/showt...hase#post61260


c) My phase shift negative 17%; its means 0.17 x 360 = - 61 degrees negative.
Timebase: 50us.
Attached picture, it looks very closely i got with pc soundcard scope.