Method for Improving RC Filter Bela Mohos,* Markus Zobrist, and Alex von Zelewsky Institute of Inorganic Chemistry, University of Fribourg, CH- 7 700 Fribourg, Switzerland
Gyorgy Galambos Department of Chemistry, McGill University, Montreal 10 f , Canada
A classical device to improve the signal to noise (S/N) ratio in spectrometry is the RC filter. T o avoid signal distortion, the efficiency of such a filter, as limited by scanning time, is given by the time constant. A possible basis for a method to improve the RC filter is the application of a long time constant to distort the signal, followed by a digital treatment to restore the original signal shape.
a
THEORY The relation between a signal y ( t ) and its distorted form Y(t) after passing a first-order low pass filter (negligible loading) with a time constant B = RC is given by Equation 1:
y(t) = 8
dY0 dt + y ( t )
it-
In the normal operation of the spectrometer, the acquisition time has to be increased until 8-dY(t) dt
