Eliminate 2 signals from 1 analog signal

[Shesha12345]

Hello Everyone,
I know some knowledge about LABVIEW coding so my problem is that I want to separate combine signals such as I am using LED of dual wave-length and I use photodiode as a detector and after some amplification and filtration I have analog waveform and I want to see my signal at a different wavelength such as 750nm and 850nm. Kindly guide me what could I do next.
Thanks for your consideration.

[Kreative24hk]

So, you have a combined analog signal which includes 750nm and 850nm wavelengths.

If you want to separate those two signal, I think you can use Filter VIs included in LabVIEW Full Development System.

VI Path : Block Diagram >> Function Pallete >> Signal Processing >> Filters

Amon that filter functions, using two of 'Equi-Ripple BandPass.vi' may help you to separate measured signal which has combining different frequency's signals. 

[Shesha12345]

Dear Kreative24hk,
Thanks for your reply but using ripple bandpass filter isn't my answer.
Actually, I have a control signal who control the initialization of LED such as 750nm and 850nm and photodiode are detected that signals as a combine and after demodulation and filtration I have a combined signal of 750nm and 850nm together. And I want to separate that 2 signal individually.
Now I have an output of filter in a waveform chart.
And I want 2 waveform chart of 750nm and 850nm respectively.
I hope you understand my desired result.
Thanks

I also attach my combine output after filtration.

[Henrik_Volkers]

Modulate both ligth sources with different (RF?) frequencies.

The resulting PD signal than can be filtered (or demodulated, or use a lockin) to seperate both sources.

What type of information do you need? Amplitude at wavelength? At what frequency do you expect the changes?

[Shesha12345]

Thank you sir for reply,

Actually my Trig frequency is 40Hz and RST frequency is 1Hz. It's mean 20Hz for 750nm and 20Hz for 850nm wavelength in 1 sec RST signal.

And photodiode detect my combine signal so after amplification and demodulated my signal and after filtration I have a combine signal of 750 and 850nm.

Now I want to separate my signal in two different graph such as 1 graph for 750nm and other graph for 850nm wavelength.

I think I can do that but how that is the problem?

Please gave me any guidance how I separated my signals.

Thanks 

[Henrik_Volkers]

How are the LEDs controlled?

What do you use to read the photodiode (DAQ?)

[Shesha12345]

Yes for generating the TRIG signal and RST signal I using DAQMX USB-6002 and also I use Analog Input to measure the output of photodiode after filtration.

[Henrik_Volkers]

I never used a 6002 and it seems that it is one of these devices not really made for synchronised AI and DO ....

You not really descriped how you control the LEDs ... each one need a dedicated turn on (TRG) and turn off line (RST)?

Seems that you can do a hardware timed DO and sync your AI. Alternate the LEDs power and cut (not filter) the AI input accordingly.

Another point is your PD circuit. Don't know if it looks like expected, but for me it looks like it needs some improvement to be faster (TIA?).

(and if you hit the Print button (or ALT-Print) you can make a screen shot copy and use a grafik program to (cut and) save it as a PNG ... much better quality 😉 )

[Shesha12345]

Thanks for Reply,
Actually, first I generate two analog output by using DAQmx 6002 that two signals are TRIG and RST. For every rising edge LED 750nm glow then 2nd rising edge LED 850nm to glow and this is carry-on. And I use photodiode OPT101 which detect these signals and forward to (PGA711) then PGA amplifies that signal and forwards to LOCK-IN modulation-demodulation IC and after demodulated I use Butterworth low pass filter and after filters, I have a combined signal of LED 750 and 850nm. Then I use the Analog Input channel to detect that output of filters.
Now I need a solution to How I can separate these combine signals.
If you need some more information please let me know I will give you.
This project is very important for me so please guide me or gave me some clue or share some related examples that helps so much.

Thank you so much for your consideration. 

[Henrik_Volkers]

Sorry it's still unclear to me how the signal you measure with the 6002 is related to the information you want to extract.

Without knowledge of

• what you want to measure and
• how the signal is processed  (oh you have some sort of lock-in IC ? What does it do to the signal ? how is it setup, and controled?

I can't help you unless my crystal-ball is back from recalibration after it unforseeable dropped from the table 😉