| 摘要 |
A variable voltage to be logarithmically indicated is fed to an input of an operational amplifier acting as a constant-current source in charging or discharging a capacitor at a constant rate determined by the magnitude of that voltage. The time required for the capacitor to charge or discharge from a reference potential to a potential equal or proportional to the variable voltage (or vice versa) is measured by a digital counter to which the output of a constant-frequency pulse generator is supplied, during the charging or discharging interval, through a binary frequency divider with a multiplicity of cascaded binary stages which are progressively cut in or out by a programmer responding to a predetermined number of pulses in the divider output, thereby modifying the pulse rate in the divider output in discrete steps by a factor of 2. Intermediate steps, designed to provide a closer approach to a logarithmic function, involve the alternate insertion of two final stages of stepdown ratio 5:1 and 7:1 in cascade with the binary stages to establish a pulse-rate modification by a factor of approximately 2ROOT 2. |
