I have two current signals from a two color Si-photodiode/PbS-photodetector. I want to measure the signal with the Stanford Research Lock-In Amplifier 830. I read in the manual that I can measure currents with the SR830. Does anyone have experience with this? Do I get better signals if I first convert my current signal into a voltage signal? I read that I could do this with the SR570 - but it seems me a little bit expensive. Is there any cheaper solution? I am a chemist and electrical things are totally new for me - I will really appreciate any answer!