| 摘要 |
PURPOSE:To detect a liquid level with higher order by feeding back the output light intensity from a light source and comparing an output signal from a light source driving circuit with a signal from a detection part for measurement and calculating it. CONSTITUTION:When a driving command signal is sent from a comparison circuit 11 to a LED driving circuit 13, an intense optical signal is outputted and inputted to a sensor head 23 for reference and a sensor head (detecting part) 25 for the signal. Then, the signal inputted to the head 23 detecting part is converted into the electrical signal in accordance with the intensity of the optical signal with a reference photodetection means 1 (a ferrule 3, etc.) and afterwards, amplified 9 and compared with an output value from a reference voltage circuit 7 with the circuit 11 and calculated therewith. On the other hand, the signal inputted to the head 25 is converted into the electrical signal in accordance with the intensity of the optical signal with a photodetection means 29 (a ferrule 27, etc.) for the signal and afterwards, amplified 33 and given to a comparison circuit 35 and compared with an output signal value from the circuit and calculated therewith. Then, arithmetic operation is performed based on output signal values from the amplification circuit 33 and the circuit 13 and the quantity of loss in the head 25 is calculated, by which the liquid level can be detected with high accuracy. |
