Phase Difference

[Clint1000]

I think you're understanding what I've been trying to explain. Using the Rotor/stator schematic and the waveform capture is exactly what I'm doing. If you only use S3>S1 you see, I'm assuming ,as the stator moves the amp changes and at the same time the phase of S3>S1 relative to R1>R2 is shifting. My wings only move +30 to -30 full range. I use the formula for synchros and Moogs data sheet to get. Deg=Invsin of ((Vp measure on S3>S1)divided by (5.25 vrms ( my applied R1>R2) * 2.203 ( the coupling ratio of the synchro *1.414( convert to rms)). So if I measure 5.59 Vp on S3>S1 using the formula above: Invsine of=(5.59/(5.25*2.203*1.414))= 20 DEGS.

[Henrik_Volkers]

S1-3 means all three legs Sx/rtn ... and ref , 4 channels.  Other configurations are just math then...

10kSPS at least... 50kSPS would be fine

Again: What is the target angular resolution needed?

[Clint1000]

My S3>S1 was a differential measurement ref.  My resolution needs to be +/-1 degree.

[Henrik_Volkers]

I attached a vi with the 'Ben' reconstruction ..  The recalculation you used (make it a sin and cos) is from the old days of analog computing 😉

depending of the connections you need to swap the angle sign and add an offset.

DAQ configuration needs to be done before running.

Since I had  no DAQ and synchro it's barely untested 😉

Hey NI, I want a configurable DAQmx simulator 😄 😄

EDIT should have added a save feature to get raw data 😄

[Henrik_Volkers]

For a maybe curious Ben: 😄

and see an error .. not really harming in this case ... phase difference 😉 

[Clint1000]

You are kind of doing what I did except..

1) I don't use producer consumer to read/analyze the signals.  I read the data in w my daq then analyze it.

2)It looks like you subtract the ref freq from each leg of the synchro freq.  I do that except on only one leg..not the other 2.

3) You then add 90 to this phase??? Why??  Then divide by 360..then subtract 90 from the remainder.

4) If this result is great than 90 you negate it.  Otherwise you send it straight thru to polar to complex..

5) you then have a polar form in real and imaginary.  One at 0, 2pi/3 and 4pi/3

6) Now back to rectangular form..get the angle of all 3 stators added together and convert that result (radians) to degrees.

7) What is swap sign for??  What is angle offset??  What is wrap in -90 to 270?

Maybe you could explain why you do all 7 steps??

Like I've been saying all along.  I only measure S3 to S1...differentially.  Why do I need the other 2 stators when they will just be 120 degs out from my S3>S1 measurement??  Why take 2 measurements just to add or subtract 120 from them to get what I measured on S3>S1 ??  Why measure w extra hardware just to do a math calculation of addition or subtraction in SW??

Could I use your method above w just one stator measurement relative to the rotor measurement?

thxs

[Henrik_Volkers]

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@Clint1000 wrote:

You are kind of doing what I did except..

1) I don't use producer consumer to read/analyze the signals.  I read the data in w my daq then analyze it.

2)It looks like you subtract the ref freq from each leg of the synchro freq.  I do that except on only one leg..not the other 2.

3) You then add 90 to this phase??? Why??  Then divide by 360..then subtract 90 from the remainder.

4) If this result is great than 90 you negate it.  Otherwise you send it straight thru to polar to complex..

5) you then have a polar form in real and imaginary.  One at 0, 2pi/3 and 4pi/3

6) Now back to rectangular form..get the angle of all 3 stators added together and convert that result (radians) to degrees.

7) What is swap sign for??  What is angle offset??  What is wrap in -90 to 270?

Maybe you could explain why you do all 7 steps??

Like I've been saying all along.  I only measure S3 to S1...differentially.  Why do I need the other 2 stators when they will just be 120 degs out from my S3>S1 measurement??  Why take 2 measurements just to add or subtract 120 from them to get what I measured on S3>S1 ??  Why measure w extra hardware just to do a math calculation of addition or subtraction in SW??

Could I use your method above w just one stator measurement relative to the rotor measurement?

thxs

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In a first guess it shouldn't make a difference if you measure Sx/rtn or Sa/Sb ...

If you use all channels you get a much better signal

After building the difference to the ref, the result could be anywhere between -+360° (or +-720° didn't check) .  The +90,remainer from 360,-90 will wrap the phase always into the -90 to 270 region. Now you need to decide the sign, wether the phase is ~0° or ~ 180° ,  90° is the boundary 😉 .

The complex math will result in the absolute position of the  synchro . Since the rotation sign and zero position depend on the way you connect the synchro signals (no matter how you do it , swapping polarity or a leg, it will still work, just change the zero and rotation direction), I added sign and offset .

Hook it up, turn the servo , check if the angle direction match or invert it , put the synchro (coarsly) into the your zero position. you should find an angle coarsly around ~+-n*30° , enter -+n*30 as your offset ... Setup DONE 🙂 Test , report here 😉

Why do I need the other 2 stators when they will just be 120 degs out from my S3>S1 measurement? As said alrady, that signal is about zero at the position you eagely want to measure, but the zero crossings are not perfekt in synchros ..

Could I use your method above w just one stator measurement relative to the rotor measurement?  No. There are other methods possible, but this one is the best AFAIK. Do you run out of channels? Or copper?

[Clint1000]

THANKS!!!!!  I'll give it a shot .  Give me 5 North American business days and I'll report back.  Lots of hardware changes now !

One question.  I'm ( will be 0 doing a single measurement at a time of all 3 stators ( after I chg based on your suggestion).  It shouldn't matter if I use consumer/producer or just a straight DAQ setup would it.  I'm not doing a continuous measurement.  Take a reading..analyze ..pass/fail.

Thanks for sticking this out.

[Henrik_Volkers]

If you use the cosumer part, you just have to make shure that the first channel is the reference in the array of wfrms.

A continious read would ease the setup of sign and offset, but since I don't know what else is done with the DAQ and where the synchro is mounted ....

[Clint1000]

I'm trying to follow your connections based on the schematic of LV you posted.  In the section labeled "wrap in -90 to 270" you measure phase w the extract single tone measurement.vi.  In one path you use phase and the other, if the resultant phase is >90, you negate the amplitude of the measured signal and use that as your phase??  Why?  To me that doesn't make sense to use phase in one case and amplitude in the other.  

Thxs