NI Lock in Amplifier

[ubongakpabio]

I am designing a simple opto-electronic circuit, to determine the chemical concentrationof an unknown sample. The red light on the reference shows there is something wrong. Have tried all I could do, but still cant figure this out. I modulated the signal to my LED as a square wave, and am supposed to have a representation of a square wave. Any ideas would be appreciated. Attached is the image

 I am design an instruments to measure the chemical concentration of an unknown sample. the circuit design entails an LED as a light source, which emits light of a particular wavelength through the sample solution, a detector, which converts the light signal into an electrical signal. the concern is that am trying to use a lock in amplifier to ensure that that's only light from the LED is detected. I had modulated the signal to my LED with a figure wave. I seem not to get the correct representation using my lock in amplifier directory on labview. Any ideas would be appreciated

[JosephP]

Hi,

Can you up upload your code as this will allow people to understand your application a lot better and will make it easier to try and help you troubleshoot?

Best regards,

Joe