Non-linear ranging to control linear ranging measurement device

This invention relates generally, as indicated, to non-linear ranging to control a linear ranging measurement device, and, more particularly, to apparatus and method employing a non-linear device to select respective ranges of a linear measurement device to measure signals over a wide range of magnitudes. A range selection circuit (), including a logarithmic amplifier () and output circuitry () associated therewith, is configured to directly drive linear ranging circuitry for measurement circuitry () in an optical power meter () to measure signals that vary over a wide range of, for example, from about −7 dB to about −45 dB. This allows the optical power meter to change ranges as fast as one (1) times the hardware settling time. The range selection circuitry is in parallel with the measurement circuitry, which allows ranging to happen in real time.