The **OARS1-R002** is a high-precision, surface-mount (SMD) current sense resistor manufactured by TT Electronics/Welwyn. It is part of the OARS (Open Air Resistor Series) family, specifically designed for high-current sensing applications. --- ### 1. Key Technical Specifications The "R002" suffix denotes the resistance value, which is 2 milliohms ($0.002 \Omega$). | Feature | Specification | | :--- | :--- | | **Resistance Value** | $0.002 \Omega$ (2 m$\Omega$) | | **Power Rating** | 1 Watt (at 70°C) | | **Tolerance** | $\pm 1\%$ (Standard for this series) | | **Temperature Coefficient (TCR)** | $\pm 40 \text{ ppm/}^{\circ}\text{C}$ | | **Operating Temperature** | $-55^{\circ}\text{C}$ to $+160^{\circ}\text{C}$ | | **Package / Case** | Surface Mount (SMD) - Elevated "Open Air" | --- ### 2. Design and Construction The OARS1-R002 has a unique physical profile compared to standard flat chip resistors: * **Elevated "Open Air" Design:** The resistive element is arched or raised above the PCB surface. This allows air to circulate underneath the part. * **Thermal Management:** By raising the hot spot away from the PCB, it prevents localized heating of the solder joints and the board material (FR4), which reduces the risk of thermal fatigue or board delamination. * **Flameproof:** The metal alloy construction is inherently flameproof. --- ### 3. Applications Because of its extremely low resistance and high precision, it is typically used for: 1. **Current Sensing:** Measuring current flow in power supplies by monitoring the voltage drop across the resistor ($V = I \times R$). 2. **Motor Control:** Monitoring torque and speed in automotive or industrial motors. 3. **Battery Management Systems (BMS):** Tracking charge and discharge cycles in electric vehicles or large battery packs. 4. **DC-DC Converters:** Providing feedback for regulation in high-efficiency power modules. --- ### 4. Advantages * **Low Inductance:** The strip-metal construction ensures very low self-inductance, making it suitable for high-frequency switching circuits. * **High Stability:** The metal alloy element provides excellent stability over time and temperature compared to thick-film alternatives. * **Solder Joint Integrity:** The flexible "U" shape of the element acts as a strain relief, absorbing the stress of thermal expansion and contraction.