Data Capture and Processing in Chemical Relaxation Measurements

Abstract

The old method to evaluate relaxation jump experiments is to photograph the trace on the oscilloscope screen and to plot the measured amplitudes against time on semilogarithmic paper. An improved evaluation technique introduced by Crooks et al. [1] eliminates the amplitude measurements (and the error introduced by the imperfection of the oscilloscope). The photographed relaxation trace is projected onto the same oscilloscope screen which has been used for the actual experiments, and an exponentially decaying time function is generated with a suitable RC network on the scope. The amplitude and time constant of this function are varied until the projected curve on the scope is matched. The method has been extended also for two relaxation times. This technique is a definite improvement, though still dark room work is necessary, and the results are not available immediatedly after the experiment. Another more convenient version of this technique consists in using a digital oscilloscope with alternating points from the relaxation experiment proper and from the simulated exponentially decaying curve. A faster matching without photographic work can thus be realized. Both techniques, however, do not allow signal averaging (see below).