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Old 2nd January 2013, 06:36 AM   #1431
RNMarsh is offline RNMarsh  United States
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Did you also try a tracking notch filter or parallel tracking notch/comb filters to remove Harmonic components?

Last edited by RNMarsh; 2nd January 2013 at 06:38 AM.
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Old 2nd January 2013, 06:44 AM   #1432
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by davada View Post
This is the circuit used and spectrum of the output.

For 6Vrms input to the lamp there is a 5.56Vdc output.
At 3Vrms the output drops to 0.823Vdc.

That's not very linear.

I'm concerned about the level of distortion as well.
This is with a 0.1uF feedback cap on the output amplifier.
I's much worse with out the cap.
R is 10M.
Its a lot worse than the results shown in the left paper/page. Why is that?
-RNM
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Old 2nd January 2013, 11:38 AM   #1433
dimitri is offline dimitri  United States
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Quote:
multiplier
Why not two of them in control loop: (A*sin(wt))^2+(A*cos(wt))^2)=A^2, no ripple (in theory)
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Old 2nd January 2013, 01:19 PM   #1434
davada is offline davada  Canada
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Quote:
Originally Posted by dimitri View Post
Why not two of them in control loop: (A*sin(wt))^2+(A*cos(wt))^2)=A^2, no ripple (in theory)
In a perfect world Dimitri.

The Sin and Cos terms have to be exactly matched or it gets really ugly.
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Old 2nd January 2013, 01:26 PM   #1435
davada is offline davada  Canada
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Quote:
Originally Posted by RNMarsh View Post
Its a lot worse than the results shown in the left paper/page. Why is that?
-RNM

System as a whole here. Lamp plus detector.
we are very demanding. What you see wound not show on a chart.
The lumens of a lamp driven from AC is not necessarily linear.
I don't have equipment to measure this.

It shows up in the multiplier gain constant chart.
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Old 2nd January 2013, 02:07 PM   #1436
davada is offline davada  Canada
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Originally Posted by 1audio View Post
My Boonton does the frequency trim through an optoisolated link. I get very good phase noise plots with it. If you have the local loop for stabilizing the oscillator then the control loop doesn't need to be very quick at all. For frequency they use JFET switches for both resistors and caps. Today I would use a controlled resistor array and switch the caps with JFETS. Then the final steering would be using a 4 Q multiplier. The PLL code would be the most difficult to get right.
This is an interesting looking IC.
Do you know who sells them?

Are the distortion figures with or without op amps?
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Old 2nd January 2013, 02:35 PM   #1437
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The Sin and Cos terms have to be exactly matched or it gets really ugly.
Have you tried it? Even with several percent amplitude mismatch output ripple is likely still much lower than for an average or RMS detector (with the same filtering). And you can easily trim the amplitude match for each range.

The S & H peak detector is cleary better, but also more difficult to implement right.

Samuel
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Old 2nd January 2013, 04:29 PM   #1438
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by davada View Post
System as a whole here. Lamp plus detector.
we are very demanding. What you see wound not show on a chart.
The lumens of a lamp driven from AC is not necessarily linear.
I don't have equipment to measure this.

It shows up in the multiplier gain constant chart.
Being a test equipment junky, I can loan you the equip to measure Lumens... if you want to know more about this.
For any system, just need to know if it can be linearized easily and affectively.

-RNM

Last edited by RNMarsh; 2nd January 2013 at 04:32 PM.
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Old 2nd January 2013, 07:15 PM   #1439
davada is offline davada  Canada
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Originally Posted by RNMarsh View Post
Being a test equipment junky, I can loan you the equip to measure Lumens... if you want to know more about this.
For any system, just need to know if it can be linearized easily and affectively.

-RNM
Thanks Rick.

It doesn't matter that much. I'm interested in the system as a whole.
The lumens for this lamp at 18V is 1.89.
The linearity of the system is more important. How much distortion is added.
There is some signal transmitted by the lamp to the optical sensor and it is this I'm looking at. What saw on the I posted is about 5% distortion. That's too much for such small signal. So I will try something else. The linearity of the device I used depends on the wave length of the source according to the data sheet IIRC. There is either a positive or negative tempco also dependant on the wavelength of the source.

I have some LDR around somewhere but have I no idea what they are. I think I got them from Radio Shack. When they where still called that in Canada.
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Last edited by davada; 2nd January 2013 at 07:35 PM.
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Old 2nd January 2013, 07:31 PM   #1440
davada is offline davada  Canada
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Originally Posted by Samuel Groner View Post
Have you tried it? Even with several percent amplitude mismatch output ripple is likely still much lower than for an average or RMS detector (with the same filtering). And you can easily trim the amplitude match for each range.

The S & H peak detector is cleary better, but also more difficult to implement right.

Samuel
Hi Samuel,

No I haven't tried it outside spice. What I saw from spice was not to promising.
Some one did try this and posted the results in one of the threads saying the ripple wasn't much better than more conventional methods IIRC.

I don't mind trying anything but then I don't get too far along on this project.

At 1KHz the output from an AD536A is quite acceptable. All harmonic appear to below -130dB. I have to confirm this once I have the Twin T built and my EMU0204 arrives.
Then I have something to compare the QA400 to.

Cheers,
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