The **S-156-R** typically refers to a high-voltage, high-reliability **Reed Relay** manufactured by companies like **Standex Electronics** (formerly MEDER electronic). These components are designed to provide physical switching with high isolation in a compact footprint. --- ## Technical Specifications | Parameter | Specification (Typical) | | :--- | :--- | | **Contact Form** | 1 Form A (Normally Open) | | **Coil Voltage** | 12V or 24V DC (Variant dependent) | | **Max Switching Voltage** | Up to 1,000V DC | | **Max Switching Current** | 1.0 Amps | | **Max Power Rating** | 100 Watts | | **Contact Resistance** | < 150 mΩ | | **Isolation Voltage** | 4kV to 10kV DC (Across contacts/coil) | --- ## Key Components & Construction ### 1. The Reed Switch The heart of the S-156-R is a hermetically sealed glass tube containing two ferromagnetic blades (reeds). These are plated with precious metals (usually Rhodium or Iridium) to prevent oxidation and ensure a long life cycle (millions of operations). ### 2. The Electromagnetic Coil Wrapped around the glass reed switch is a copper wire coil. When current flows through this coil, it generates a magnetic field that pulls the two reeds together, closing the circuit. ### 3. Encapsulation (The "R" Suffix) The "R" in the part number often signifies **Resin** encapsulation or a specific **Ruggedized** housing. * **Protection:** Protects the delicate glass switch from mechanical shock and vibration. * **Insulation:** Provides high dielectric strength, allowing the device to handle high voltages without "arcing" to nearby components. --- ## Operation Principle The device operates based on simple electromagnetism: 1. **De-energized State:** The reeds are separated by a small gap. The circuit is "Open." 2. **Energized State:** DC voltage is applied to the coil pins. The resulting magnetic field magnetizes the reeds with opposite polarities. 3. **Closing:** The opposite poles attract, the reeds touch, and the circuit is "Closed." --- ## Common Applications * **Test and Measurement:** Used in Automated Test Equipment (ATE) for high-voltage insulation testing. * **Medical Equipment:** High isolation makes them ideal for defibrillators or imaging sensors. * **Renewable Energy:** Monitoring isolation resistance in solar inverters and battery management systems (BMS).