1 You must measure simultaneously your reference signal and your weak signal (VI AI Multi PT), 2 you must "center" your two signals (substract their mean) 3 you multiply "point to point" your signals, you obtain a signal, 4 then the result is the sum (or the mean) of this signal. (after 2, you may too compute a "scalar produce" (produit scalaire in french). This result is proportionnal to the amplitude of the weak signal, multiplied with the cosine of the dephasage between the 2 signals. So this dephasage must be constant and different from pi/2
It is possible, but more difficult to calculate the amplitude and the dephasage in all the cases.
TaeHyun a écrit dans le message : 38BF01EB.8254C81@ee.tamu.edu... > Hi.. > > I'm trying to measure ve ry weak signals so, I use a chopper which makes > a reference signal for lock-in. > And measure a spectrum from weak light signals... > > I don't know how to program a spectrum analyzer VI and Lock-in VI.. > > Please help me out.. > > Thanks in advance. > > Jongseo >