The **FLCS-21-R** refers to a specific series of high-performance **Fiber Optic Liquid Level Sensors** (often associated with manufacturers like Panasonic or specialized industrial sensor brands). These devices are designed to detect the presence or absence of liquid through the use of optical principles. ### 1. Core Operating Principle The FLCS-21-R operates on the **Total Internal Reflection (TIR)** principle. * **In Air:** Light emitted from an LED travels through the fiber optic cable to the tip. Because the refractive index of air is low, the light reflects off the prism-shaped tip and returns to the receiver. * **In Liquid:** When liquid touches the tip, the refractive index changes. The light "leaks" into the liquid instead of reflecting back. The receiver detects this drop in light intensity and triggers an electrical output. --- ### 2. Technical Specifications Table | Feature | Description | | :--- | :--- | | **Detection Method** | Optical Refraction (Prism Tip) | | **Light Source** | Infrared LED (usually 850nm - 950nm) | | **Output Type** | NPN or PNP Open Collector (depending on wiring) | | **Operating Voltage** | 12V to 24V DC | | **Response Time** | < 2ms (High speed) | | **Material** | PFA / Fluoropolymer (Chemical resistant) | --- ### 3. Electronic Component Breakdown #### A. The Sensing Head (Fiber Optic) The part ending in "-R" often denotes a specific **Radius** or **Chemical Resistance** (Fluoropolymer coating). * **Internal Fiber:** High-purity plastic or glass fibers that transmit light with minimal loss. * **Prism Tip:** A precision-molded tip that acts as the interface between the electronic signal and the physical liquid. #### B. The Amplifier Unit The fiber optic cable must connect to an external **Amplifier Unit** (like the FX-500 series). This unit contains: 1. **Emitter Circuit:** Drives the LED at a specific frequency to avoid interference from ambient light. 2. **Receiver (Phototransistor):** Converts returning light into a voltage. 3. **Comparator:** Compares the voltage against a user-defined threshold. 4. **Output Transistor:** Switches the load (PLC, Relay, or LED indicator). --- ### 4. Wiring Diagram Logic Most FLCS-21-R systems follow standard industrial color coding: ```yaml Brown: +V (12-24V DC) Blue: 0V (GND) Black: Control Output (Signal) Pink: Mode Selection (Light-ON / Dark-ON) ``` --- ### 5. Key Advantages * **Non-Electrical at Point of Contact:** Since only light enters the tank, it is safe for explosive or flammable liquids. * **Chemical Resistance:** The PFA coating allows it to be used with strong acids, bases, and ultra-pure water. * **Compact Form Factor:** Can be installed in tight spaces where mechanical floats cannot fit.