Abstract: An RMS converter has first and second transistors (40a and 42a) providing a signal representing double the log of the input voltage, a third transistor (40b), matched with the first (40a), providing a signal representative of the log of the output voltage and a fourth transistor (42b), matched with the second (42a). providing a signal representative of the anti-log of the ratio of those signals; the transistors in each matched pair are repetitively interchanged functionally thereby reducing errors caused by slight differences in the transistor operating characteristics.

Abstract: The variable attenuator and variable current shunt of a battery-powered auto-ranging digital multimeter uses latching relays, each of which, since it is stable in each of its two switching states, requires only a current pulse to change its state. The circuit which operates the relays provides a drive pulse only when the desired relay state differs from the actual state, thus minimizing the power required, and includes a tank circuit for minimizing disturbance to the multimeter power supply. To ensure that the tank circuit can recharge, each relay is driven by a tri-state output.