AC/DC converter - adapter for DC meters

7-88 — elektor july/august 1982 This AC/DC converter "translates" the value of an AC voltage into a corresponding DC voltage. It allows AC voltages to be measured with the aid of a high impedance (DC voltage) voltmeter. The circuit diagram shows an active rectifier which is designed around a CA3130. It contains a few little tricks that make it possible to ap- proach the effective value measure- ment as closely as possible. The signal to be measured is fed to the non-inverting input of IC1 via input capacitor Cl. Diodes D3 and D4 protect the input against excessive voltages. The capacitors C4/C6 and C2 make sure that the output and negative feedback are only AC coupled, so that any offset of IC1 will not effect the measurement result. Resistors RI and R2 look after the DC setting of the IC, while R3 takes care of the DC amplifi- cation factor (1x). Bootstrapping is achieved by C2, which consider- ably increases the input impedance of the circuit. D2 will conduct on a positive edg...