| 摘要 |
PURPOSE:To obtain accurate photometric output by removing the variation in the temp. of the bias voltage of a membrane optical sensor, by using a voltage source showing the same voltage characteristic as that to the temp. of an amplifying circuit in an output side as the power source of the membrane optical sensor. CONSTITUTION:In a photometry circuit wherein a membrane optical sensor SP2' is connected to the input terminal of an amplifying circuit OP1, the voltage characteristic to the temp. at the input terminal of the amplifying circuit OP1 is calculated. Then, a voltage source having the same characteristic as the temp./voltage characteristic thereof is provided to be connected to the terminal of the membrane optical sensor SP2' in the side opposite to the amplifying circuit OP1. In order to form this voltage source, an operational amplifier OP4 having a diode LD4 may be provided in a return path. By this method, the bias voltage of the membrane optical sensor SP2' can be removed and, therefore, accurate photometric output under no temp. change is obtained. |
