Hello,
I have a quesiton about modifying the lock-in VI shown here: http://www.ni.com/example/29532/en/. I saw some threads that discussed a similar problem, but there were no clear answers.
We have a infrared signal that is modulated at 280KHz. This signal is interfered with an equal wavelength infrared beam that is modulated at 260 Hz, which then creates a sideband with a better signal to noise compared to just when locked-in to the 280 KHz signal. So, our signal is just one input, but our reference is ONE frequency, but comes from two mixed signals. Here are some pictures of the frequency spectrum showing where we want to lock-in and the setup of the experiment (see attachements). We actually want to lock-in at a sideband of the 3rd harmonic (3*280KHz+260Hz).
I imagine we can input the two references into a daq device, but how should we modify the Lock-in amplifier VI that NI provides ("lock-in amplifier example") to mix the two reference to make the harmonic sideband reference? Can I do this in Labview? We would greatly appreciate any help! The necessary hardware to do this operation cost $30k!!!! Thank you.