Automatic calibration of logarithmic amplifier and spectrophotometer utilizing this calibration

Abstract

Abstract PURPOSE:To provide an automatic calibration method for logarithmic amplifiers, which can be used for a wide range of voltages without being adversely affected by temperatures, by calibrating a logarithmic amplifier with a control unit consisting of a micro-computer so as to obtain linear logarithmic amplification characteristics. CONSTITUTION:A signal electric current received at an input terminal 1 is applied to a logarithmic amplifier 3 through switches 2. A calibration electric current from a calibration current source 4 is also input into the amplifier 3 through the switches 2. An output from the amplifier 3 is calibrated by operating an A/D converter 6 and a control unit 7 in a predetermined manner to obtain a calibration curve 8. An amplifier calibration value, by which a logarithmic amplification value is multiplied to obtain a logarithmic amplification value based on linear characteristics 9, is then calculated in the control unit 7. The control unit 7 then outputs a true value. Thus, an excellent automatic calibration method for a logarithmic amplifier can be obtained, which has a wide range of operation and which can be used stably at a low cost for a long period of time without paying regards to temperature characteristics.

Inventors

• 👤 Shinichiro Watanabe

Bibliographic Details