Summary so far
.
Photodiodes can operate in two modes - photovoltaic and photoconductive
PMTs are usually used for fluorescence measurements
Photodiodes are usually used for scatter
PMTS are sensitive to
different wavelengths according to
the construction of the photocathode
PMTs are subject to dark current
Voltages and gain are not linear
Photodiodes are more sensitive than PMTs but because of their low gain, they are not as useful for low level signals (too much noise)