Level switch, abbreviated as LS, provides a discrete input to the PLC. It is a device used to detect the presence or absence of a liquid or solid substance at a specific level within a container or tank. The level switch is typically used as a method of control in tanks and vessels. Level switches are crucial in various industrial and commercial applications to monitor and control processes involving liquids or solids. The primary function of a level switch is to provide a signal or trigger an action when the substance being monitored reaches a certain level. This signal can be used to activate alarms, control valves, pumps, or other devices in the process.
Commom Level Switche Types
Float Level Switches - These switches use a float mechanism that rises or falls with the level of the liquid. When the liquid reaches the predetermined level, the float actuates a switch, triggering the desired response.
Capacitive Level Switches - Capacitive level switches work based on changes in capacitance between two electrodes as the level of the substance changes. When the substance reaches the electrodes, the capacitance changes, signaling the switch to activate.
Conductive Level Switches - Conductive level switches utilize the conductivity of the substance to detect its presence. When the substance bridges two conductive probes, completing a circuit, the switch is activated.
Optical Level Switches - Optical level switches use light beams to detect the presence or absence of the substance. When the substance interrupts the light beam at the desired level, the switch is triggered.
Ultrasonic Level Switches - Ultrasonic level switches use ultrasonic waves to measure the distance between the sensor and the substance. When the substance reaches the predetermined distance, the switch is activated.
Vibration Level Switch - The switch incorporates a vibration sensor, which can be based on various principles such as piezoelectric, electromagnetic, or mechanical mechanisms. This sensor detects vibrations caused by the presence or absence of material at the level being monitored.
The choice of level switch depends on factors such as the type of substance being monitored, the temperature and pressure conditions, the accuracy required, and the specific application requirements. Instrumentation level switches play a critical role in ensuring the safe and efficient operation of various industrial processes, including chemical processing, food and beverage production, water treatment, and oil and gas refining.
Configuration and Alarms
Configuration (Normal State):
- NO - Normally Open
- NC - Normally Closed
Alarms in the PLC can be:
- LSH - Level Switch High
- LSL - Level Switch Low
- LSHH - Level Switch High High
- LSLL - Level Switch Low Low
