| 摘要 |
PURPOSE:To perform zero-adjustment operation readily and accurately, by a method wherein a prescribed zero-adjusting circuit receives output from a light measuring unit, and a switch unit supplies start signal to the zero-adjusting circuit. CONSTITUTION:When output of a luminous intensity converter becomes 0 and a switch 51 is pushed, negative logic pulse is generated and fed through an inverter 53 to a monostable multivibrator 42. Output of the multivibrator resets FF 39 and a binary counter 45. Output of the FF 39 becomes 1 and is entered in NAND gate 40 to invert pulse in an oscillator 54 and supply it to the counter 45. If reset pulse is entered in R-terminal of the counter 45, the whole of bits become 0 and output voltage of DAC 46 becomes -V1. If one end 32 of input terminal of a summing amplifier 36 becomes negative, positive output of the amplifier 36 is passed through a comparator 37 and Tr 38 and holds output of the FF 39 to 1. As counting value of the counter 45 increases, output of the DAC 46 increases from -V1 towards 0 and a gate circuit 40 is closed by negative output of the amplifier 36. In this constitution, zero-adjustment operation is carried out readily and accurately. |
