| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus having a capacitive level-detecting part which can detect an impedance change with high sensitivity, by constituting a detecting circuit of the level-detecting part of a resistance valtage-deviding circuit and an operational amplifier. SOLUTION: A signal from an a.c. oscillation circuit 7 is sent to an operational amplifier 17 and a voltage-dividing resistance circuit. An output of the operational amplifier 17 is inputted to a plus terminal of an operational amplifier 13 through an operational amplifier 20. A signal from a dispenser probe 22 is inputted to a minus terminal of the operational amplifier 13 through operational amplifiers 18 and 21. Since a detecting circuit is composed of a resistance voltage-dividing circuit and the operational amplifiers, the operational amplifier is provided with a fine adjustment function, so that irregularities of a resistance value of a bridge circuit are absorbed to ensure stable operation. Moreover, in comparison with a conventional detecting circuit, an impedance change can be detected with higher sensitivity. |
