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Phase Difference

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My bad!

 

The reference and syncro signal will be in phase since the reference induces the rotor ( or vise versa).

 

The Phase enters the picture as the amplitude of the signal measured in the rotor. As in;

 

(Amplitude of Rotor) / (Amplitude of Stator winding) = Cos (Rotor Angle)

 

If the Stator signal is in phase the angle between stator and rotor is in range 0-180 degrees.

If the phase is 180 out then the rotor angle is 0- (-180).

 

Syncros used to have two windings (mentioned above) that are oriented 90 120 out from each other so when the signal gets very small the other winding can be used to get a better measurement.

 

The is some Missile Fire Control instructor pulling his hair out over my previous post.

 

See this image to try and clear up my old memory

 

Synchro.jpg

 

Ben  

Retired Senior Automation Systems Architect with Data Science Automation LabVIEW Champion Knight of NI and Prepper LinkedIn Profile YouTube Channel
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Message 11 of 42
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Just to simplify the setup.  I apply 5 vrms@400 hz to r1/r2 of a synchro.  I measure off s3 relative to rtn of the supply ( 5vrms) voltage.  From what little I understand of synchro the amplitude measured off S3/rtn is proportional to the position of the synchro.  And the phase of s3/rtn indicates clockwise or cc position.  I measure my ref signal and my S3 signal using a daq 6229.  Using extract multiple tone information.vi, I get the amplitude and phase of each of the signals.  I then subtract the 2 phases.  If its say ( a phase diff picked by me) the phase diff is more than 45 deg the they are out of phase and moved CCW.  If less, they moved CW.  I can easily measure the amp.  That's not my difficulty.  Its the phase.  I've looked at both signals on a scope and the above description "works". I can see the phase shift and the amp change relative to my ref signal.  Just can't get phase measurement to work.  All these math solution seem to be more complex than I need..plus its been a long time since I used any of them..

Does what I'm doing sound plausible??  My question is what criteria do I use to determine phase shift??  Is 45 deg reasonable?  Because of the nature of a synchro there is a slight phase shift.  Why can't i use extract multiple tone information.vi?

 

Thanks..

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Message 12 of 42
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One thing I forgot.  Does anyone know how small a signal you can measure w extract multiple tone information.vi ?  It doesn't say in help for "threshold". 

thxs

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Message 13 of 42
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Ups, I mixed up resolver (90°) and syncro (120°)... 

However I didn't get how you wire it, and why you get a phase shift... according to

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-12/ac-instrumentation-transducers...

it seems just amplitude propotional ...

 

Did I get it rigth, that the signal amplitude gets down to zero at the ideal position?

Or as I have seen it with LVDTs , the signal is not perfectly going down to zero and swap phase by 180° , is gliding to the new phase with a residual signal. BUT I wouldn't use that position for fine positioning!

 

If you read only S3 that is going to zero, how about reading S1 and S2 and compare the amplitudes ?

Or drive the syncro with a 3 phase signal and read the absolute phase?

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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Message 14 of 42
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@Clint1000 wrote:

One thing I forgot.  Does anyone know how small a signal you can measure w extract multiple tone information.vi ?  It doesn't say in help for "threshold". 

thxs


It's more about noise (quantisation and whatever you have on your signal), the amplitude doesn't matter.

If you exactly know the frequency  you can measure even signal buried in noise... LOCK-IN 😉

The tone detection works with FFT , so longer durations can help, together with the search window. BUT it is no Lock-In.)

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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Message 15 of 42
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@Henrik_Volkers wrote:

@Clint1000 wrote:

One thing I forgot.  Does anyone know how small a signal you can measure w extract multiple tone information.vi ?  It doesn't say in help for "threshold". 

thxs


It's more about noise (quantisation and whatever you have on your signal), the amplitude doesn't matter.

If you exactly know the frequency  you can measure even signal buried in noise... LOCK-IN 😉

The tone detection works with FFT , so longer durations can help, together with the search window. BUT it is no Lock-In.)

 


Lock-in is what I suggested earlier, and you too in a round-about way. You suggested fitting to (A cos(2 pi f t) + B sin(2 pi f t) ); this is what modern lock-in do. Multiply signal by cos and sin, low-pass filter, and get A and B, also called X & Y or I & Q. Phase is then an arcTan away.

 

All these math solution seem to be more complex than I need..plus its been a long time since I used any of them..

 

There is some serious "math" behind the Extract Tone Information VI, it is just hidden behind a VI. Wrap the math in a VI and don't worry about it. You don't have to understand it, you need to believe it works. So test it and see if it works.

 

mcduff

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Message 16 of 42
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@mcduff wrote:

There is some serious "math" behind the Extract Tone Information VI, it is just hidden behind a VI. Wrap the math in a VI and don't worry about it. You don't have to understand it, you need to believe it works. So test it and see if it works.

 

mcduff


He will not need a lock-in. He need a proper setup.

An ideal synco in his actual setup will go down to zero and ramp up again with 180° phase shift. Just by imperfection he still can measure a residual signal at S3  with a phase change. Not a good way to use a syncro. If he would measure S1 and S2 at the same position, he should get two signals of equal amplitude and the direction of a position missmatch is indicated by one amplitude is higher or smaller then the other. With a much better signal to noise ratio!

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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Message 17 of 42
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Lock-in is what I suggested earlier..not familiar w that terminology

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Message 18 of 42
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@Clint1000 wrote:

Lock-in is what I suggested earlier..not familiar w that terminology


Read attachment

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Message 19 of 42
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Can you explain further??  Using my DAQ I measure S1 to rtn and S2 to rtn.  If S1 or S2 is greater than the other there is a phase shift?? 

Confused by: "If he would measure S1 and S2 at the same position, he should get two signals of equal amplitude and the direction of a position missmatch is indicated by one amplitude is higher or smaller then the other".  In part of your statement you say "he should get two signals of equal amplitude " then go on to say "and the direction of a position missmatch is indicated by one amplitude is higher or smaller then the other" .  Currently I'm using amplitude to determine relative position to say center.  Think of it as looking down on a clock face w jut the hour hand.  At 3 o'clock its at position 0 deg.  At noon its at 7 vp and the phases are out of alignment ( relative to a ref voltage)  so it moved CCW.  At 6 o'clock its 7 vp and the phases are in align so I know it moved CW.  between 3 o'clock and either noon or 6 the amplitude decreases indicating its position on the clock face. 

So I need to know Vp and phase at any instant to see where I am.  Would measuring S1 and S2 still allow me to do this?

 

 

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Message 20 of 42
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