The **ESD-R-18SD** belongs to the **ESD-R-SD** series of EMI cores, manufactured by KEMET. These components are specifically designed for noise suppression in high-frequency applications, primarily used on circular cables. --- ### 1. Key Technical Specifications The "18SD" designation refers to the physical dimensions and the specific material composition used for electromagnetic interference (EMI) mitigation. | Attribute | Specification | | :--- | :--- | | **Material Type** | Ni-Zn (Nickel-Zinc) Ferrite | | **Outer Diameter (A)** | 18.5 mm | | **Inner Diameter (B)** | 10.0 mm | | **Thickness (C)** | 10.0 mm | | **Operating Temperature** | -25°C to +85°C | | **Core Shape** | Toroidal (Ring) Core | | **Flame Retardancy** | UL94 V-2 (for the coating/case) | --- ### 2. Functional Characteristics The ESD-R-18SD acts as a passive low-pass filter. It works by providing high impedance to high-frequency noise while allowing low-frequency signals or power to pass through with minimal attenuation. * **Frequency Range:** The Ni-Zn material is highly effective for high-frequency noise suppression, typically ranging from **10 MHz to 300 MHz**. * **Impedance Induction:** As noise passes through the core, the magnetic field interacts with the ferrite material, converting electrical noise energy into a small amount of heat (thermal dissipation). * **Common Mode Choke:** It is most effective when used to suppress common-mode noise on signal or power lines. --- ### 3. Application and Installation This part is commonly found in consumer electronics and industrial equipment where electromagnetic compatibility (EMC) compliance is required. #### Common Uses: * **Cabling:** HDMI, USB, and power supply cables. * **Internal Wiring:** Protecting sensitive internal circuits from external interference. * **Office Equipment:** Copiers, printers, and computers. #### Installation Methods: 1. **Single Pass:** The cable simply passes through the center of the ring. 2. **Multi-turn:** For increased impedance (better noise filtering), the cable can be looped through the core multiple times. The impedance increases proportionally to the square of the number of turns ($Z \propto N^2$). --- ### 4. Comparison of Materials (Ni-Zn vs. Mn-Zn) The **SD** suffix in this part number indicates Ni-Zn, which differs from Mn-Zn (Manganese-Zinc) cores used in lower frequency ranges. | Feature | Ni-Zn (ESD-R-18SD) | Mn-Zn (Standard) | | :--- | :--- | :--- | | **Frequency Range** | High (MHz range) | Low (kHz to low MHz) | | **Resistivity** | High (Insulative) | Low (Conductive) | | **Best Application** | Radiated noise | Conducted noise |