I am trying to design a turbidity detector and this has to be sensitive to tiniest amounts of contamination present in a sample fluid. My setup consists of a 780nm laser whose current I control with an SMU. Light from this laser passes through a cuvette which contains the fluid and the intensity of the transmitted light is detected by a photodetector using an electrometer. The laser has an in-built photodiode and I use that to monitor any change in the laser's intensity, using another electrometer built by a different manufacturer. My intent here is to normalize the transmitted intensity by the laser's input intensity, to factor out laser's intensity variation. However, the laser is pretty shabby(intensity varies a lot) and therefore I need the two instruments to be precisely time-synced when they make a measurement. What's the best way to achieve this?
What I have thought of:
Send "trigger" signal to both the devices when I want to make a measurement. The problem here is that the electrometers are manufactured by two different manufacturers and there might be a delay-to-measurement difference between the two.