| 摘要 |
PURPOSE:To absorb dispersion of characteristics of an apparatus including fiber and to optimize the concentration of ink by the improvement in detecting accuracy, by adjusting the outputs of light emitting and light receiving diodes with an operational amplifiers, which are provided in a light emitting part and a light receiving part. CONSTITUTION:A light emitting part has an operational amplifier 9 and a light emitting diode 10. The output current of the operational amplifier 9 is supplied as a base current to an emitter grounded transistor 8. The voltage of a variable resistor R3 is made constant. The current, which flows through the light emitting diode 10, is made linear with respect to the change in resistance of the variable resistor R3. A light receiving part has a photodiode 11 and first and second operational amplifier 91 and 92. The light output emitted from the light emitting diode 10 is received with the photodiode 11 through a fiber which is partly in contact with ink, which is liquid to be measured. The output converted into an electric signal is amplified in the operating amplifier 91. The output current is made variable with a variable resistor R'3. A voltage corresponding to the concentration of standard ink is obtained in the operational amplifier 92. The voltage is used for measuring the concentration of the ink in the ink feeding system of an ink jet printer. |
