The **FNS-H4W-R** is a specific model of a **water flow sensor** (often categorized under flow switches or flow meters) commonly used in industrial cooling systems, laser equipment, and water treatment machinery. Below is a detailed breakdown of its electronic components and technical specifications. --- ## 1. Technical Specifications The device acts as a transducer, converting the mechanical kinetic energy of water flow into an electrical signal. | Feature | Specification | | :--- | :--- | | **Model** | FNS-H4W-R | | **Switching Element** | Micro-switch (Snap-action) | | **Contact Arrangement** | SPDT (Single Pole Double Throw) | | **Max Voltage** | 250V AC / 125V AC | | **Max Current** | 15A (Resistive load) | | **Protection Rating** | IP54 (Dust and splash resistant) | | **Connection Size** | Usually 1/2" or 3/4" NPT/G | --- ## 2. Key Electronic & Mechanical Parts ### A. The Micro-Switch (Core Electronic Component) Inside the casing is a heavy-duty micro-switch. Unlike digital sensors that use Hall Effect sensors, the "R" series typically uses a mechanical contact switch. * **Function:** When flow reaches a set threshold, the mechanical arm triggers the switch. * **Wiring:** It features three terminals: **COM** (Common), **NO** (Normally Open), and **NC** (Normally Closed). This allows the sensor to either start a pump when flow is detected or trigger an alarm if flow stops. ### B. The Internal Bellows The electronic switch is isolated from the water by a metallic or rubber bellows system. * **Role:** This ensures that the electrical housing remains dry. It translates the movement of the paddle (in the pipe) to the switch plunger inside the dry housing. ### C. Sensitivity Adjustment Screw Located near the electronic switch, there is usually a range adjustment screw. * **Electronic Impact:** Turning this screw changes the spring tension, effectively altering the "Trip Point" (the flow rate at which the electrical circuit closes or opens). --- ## 3. Wiring Diagram Logic To integrate the FNS-H4W-R into a system, the following logic is applied: ```mermaid graph LR A[Power Source] --> B[COM Terminal] B --> C{Flow Detected?} C -- YES --> D[NO Terminal -> System Runs] C -- NO --> E[NC Terminal -> Alarm/Stop] ``` ### Typical Usage Scenarios: 1. **Safety Interlock:** If the cooling water for a spindle or laser tube stops, the NC circuit closes, sending a signal to the PLC to E-stop the machine. 2. **Pump Control:** The NO circuit closes once flow is established, signaling that it is safe to engage high-power heaters or components. --- ## 4. Maintenance Notes * **Contact Pitting:** Because it is a mechanical switch, switching high-inductive loads (like large motors) directly can cause "pitting" on the electronic contacts. It is recommended to use an intermediate relay. * **Insulation:** Ensure the cable gland is tightened to maintain the IP54 rating and prevent moisture from shorting the electronic terminals.