Why we more noise in PDA detector compared to UV detector?






Why we more noise in PDA detector compared to UV detector?..

Answer / anil

There is no Integration function in the conventional UV-Vis spectrophotometer which
accumulates the signal. For example, the total required time will be 1000 sec. for 1000 data
points and it takes 1 sec. to measure one datum. In this case, all 1000 data have the same signal
to noise ratio (S/N).
But in a PDA instrument which has a 1000 photodiode array, 1000 data points can be
measured in 1 sec. and it would take 1/1000 sec. to achieve the same result obtainable in 1 sec.
in a conventional instrument. Therefore, when the same sample is measured for 1000 sec in a
PDA instrument, the signal is accumulated and is 1000 times greater than when measuring for 1
sec. The noise will be 10001/2
. This means that the S/N ratio is improved by 10001/2
.
This resulting benefit of fast data acquisition is termed Felgett’s S/N Advantage or
Multichannel Advantage

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