The **W0402R-12-RDI** is a high-precision, thin-film surface mount resistor manufactured by **TT Electronics/Welwyn**. It belongs to the **W series**, which is renowned for its excellent stability and reliability in demanding electronic circuits. --- ## 1. Technical Specifications The part number follows a specific coding convention that defines its electrical characteristics: | Parameter | Specification | | :--- | :--- | | **Resistance Value** | Defined by the "RDI" suffix (usually requires specific value lookup) | | **Case Size** | 0402 (1.0mm x 0.5mm) | | **Technology** | Thin Film (Metal Film) | | **Tolerance** | Typically ±0.01% to ±0.1% (High Precision) | | **Temperature Coefficient (TCR)** | ±10 ppm/°C to ±50 ppm/°C (indicated by "12") | | **Power Rating** | 0.063 Watts (1/16 W) | | **Operating Temperature** | -55°C to +155°C | --- ## 2. Key Features * **High Precision:** Thin-film technology allows for extremely tight tolerances, making it suitable for applications where signal accuracy is critical. * **Low Noise:** Thin-film resistors exhibit significantly lower current noise compared to thick-film alternatives. * **Stability:** Designed to maintain its resistance value over long periods and under varying environmental stresses (moisture, heat). * **Compact Form Factor:** The 0402 package is ideal for high-density PCB designs in modern portable electronics. --- ## 3. Typical Applications The W0402R series is commonly found in circuits that require high signal integrity: 1. **Medical Instrumentation:** Precision monitoring and diagnostic tools. 2. **Telecommunications:** Signal processing and base station equipment. 3. **Industrial Controls:** Sensor interfaces and feedback loops. 4. **Test & Measurement:** Calibration equipment and multimeters. --- ## 4. Understanding the Part Number Code ```text W 0402 R - 12 - [Value] [Tolerance] | | | | | | | | | | | +-- Packaging/Tolerance | | | | +------------ Resistance Value | | | +------------------- TCR Code (12 = 10ppm/°C) | | +------------------------ Resistor Type (Thin Film) | +----------------------------- Size (0402) +--------------------------------- Series (Welwyn Precision) ```