| 摘要 |
Apparatus and method for correctly detecting the level of a processing liquid such as HPM in a processing tank in the event that any drift occurs in a detector is disclosed. A liquid level detecting apparatus (70) comprises a pressure sensor (73) operable to generate an output signal S0 which is maintained at a constant signal level until the level of HPM reaches a predetermined position M in the tank and rises in the signal level as the liquid level rises in the tank after reaching the predetermined position M, a determination circuit (93) for determining whether the liquid level reaches the predetermined position M and a liquid level detecting circuit (94) for detecting the liquid level. The output signal S0 from the pressure sensor is input to an amplifier (92). The liquid level detecting circuit (94) comprises a low-pass filter (97) which receives the amplified signal and generates an output pressure signal S4. The liquid level detecting circuit (94) is operable to calculate any difference between the output signal S4 from the low-pass filter and a correction signal DELTAS generated by a signal holding circuit (98).
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