The **FT-R31** is a high-performance fiber optic sensor head manufactured by **Keyence**. It belongs to the thrubeam type fiber sensor category, specifically designed for liquid level detection or presence sensing in tight spaces. --- ### 1. Core Technical Specifications The electronic and physical performance of the FT-R31 is characterized by the following parameters: | Feature | Specification | | :--- | :--- | | **Fiber Type** | Thrubeam (Emitter and Receiver separate) | | **Fiber Diameter** | ø1.0 mm × 2 | | **Fiber Length** | 2 meters (Standard) | | **Minimum Bend Radius** | R2 mm (High-flexibility) | | **Detecting Distance** | Depends on the connected Amplifier (e.g., FS-N series) | | **Environmental Resistance** | IP67 (Waterproof/Dustproof) | --- ### 2. Key Electronic Components & Materials The FT-R31 is a passive component, meaning it does not have internal circuitry like a transistor. Instead, it relies on optical physics and material science to interface with an electronic amplifier. #### A. Optical Fiber Core (The Data Path) * **Material:** Plastic (Polymethyl Methacrylate - PMMA). * **Function:** Conducts the light beam from the amplifier's LED to the sensing point. The core is designed for low attenuation to ensure high signal-to-noise ratios. #### B. The Sensor Head (Optical Interface) * **Housing:** Typically stainless steel or high-grade plastic. * **Lens System:** The R31 uses a side-view or space-saving layout. The internal prism or lens redirects the light 90 degrees or focuses it into a narrow beam to detect small objects. #### C. Fiber Sheathing * **Material:** Polyethylene (PE) or Fluororesin. * **Electronic Importance:** Provides electrical insulation and prevents electromagnetic interference (EMI) from affecting the light path, which is a primary advantage over traditional copper-wire sensors. --- ### 3. Electronic Integration (Amplifier Unit) To function, the FT-R31 must be connected to an **Amplifier Unit** (such as the Keyence **FS-N40** or **FS-V30** series). The electronic process follows this chain: 1. **Light Emission:** The amplifier’s internal LED (usually Red) pulses light into the FT-R31 emitter fiber. 2. **Transmission:** Light travels through the fiber core via total internal reflection. 3. **Reception:** The FT-R31 receiver fiber catches the light and returns it to the amplifier’s **photodiode**. 4. **Signal Conversion:** The photodiode converts the light intensity into an electrical voltage/current. 5. **Output:** The amplifier’s CPU compares this value to a threshold and triggers a digital output (PNP/NPN). --- ### 4. Application Advantages * **EMI Immunity:** Since the "part" in the sensing area is purely optical fiber, it is immune to electrical noise from motors or high-voltage lines. * **Explosion Proof:** No electrical current flows through the FT-R31 head, making it safe for hazardous environments. * **Compact Form Factor:** The R-series (Radial/Side-view) allows for installation in electronic assembly lines where vertical space is limited.