| 摘要 |
PROBLEM TO BE SOLVED: To provide a cheap liquid level detection device with a simple constitution capable of inhibiting an influence on liquid level detection by a stray capacitance variation caused by a vertical and rotation motion of a sampling arm. SOLUTION: Liquid 5 is separately poured to a container 3 of a retaining portion 4 and liquid level is detected by a probe 6. In the liquid surface detection device, the probe 6 is made to a shield drive which is constituted by an operation amplifier between an inner tube 6a and an outer tube 6b of the probe 6 and the outer tube 6b is not earthed and is made to a low impedance at the same potential as the inner tube 6a. Since the inner tube 6a and the outer tube 6b have the same potential, an electrostatic capacity between them is 0 and a variation of the electrostatic capacity is not generated caused by a descending of the probe 6 and a position deviation of a wiring. A difference of a capacity when the probe 6 is contacted with the liquid and a capacity when the probe 6 descends becomes a capacity between the probe 6 and the retaining portion 4 and a stable liquid surface detection becomes possible. |
