| 摘要 |
<p>A liquid level control system is disclosed. The system includes at least one level sensing electrode which is fixedly mounted to a vessel and projects therein. The probe is adapted to contact a fluid within the vessel to utilize the electrical conductivity of the fluid to complete a circuit when the fluid contacts the probe. The probe is coupled between a point of reference potential and the control electrode of a single silicon controlled rectifier (SCR). The main electrodes of the SCR are serially coupled with the coil of a low-voltage A.C. relay and the secondary winding of a step-down transformer. Accordingly, the use of a relatively low secondary voltage avoids shock hazards; and, the sensitivity of the system is increased by the effective gain provided by the SCR. The use of an A.C. current in the probe avoids the galvanic corrosion which otherwise follows from D.C. current operation.</p> |
