Abs / Rms / Log Converter

013 TEST & MEASUREMENT ABS / RMS / LOG CONVERTER The converter is specially intended for use in audio applica- larly suitable. The is derives three voltages from the input signal: tions for which the lc used, a Type SSM2210 from Pm", is particu- one corresponding to the absolute-Ass-value; one correspon- ELEKTOR ELECTRONICS JULY 1989 SUPPLEMENT ing to the root-mean square-inks-value; and the third corres- ponding to the logarithmic-Loc -value of the input current, since the is operates with currents. This makes possible a wide dynamic range: something like 100 dB. Translated into terms of input current, that gives 3 mA (p-p) to 30 nA (p-p). This makes it vital that Cl is a type with a very small leakage current. The input voltage is converted into current by Rl. With a value as shown for this component, the nominal input level is 0 dBV with a reserve up to +20 dBV. Like the input signal, the output signals are currents that are converted into voltages by opamps Al, A...